:root {
    --color-primary: #004EA1;
    --color-primary-dark: #003a7a;
    --color-primary-light: #e6f0fa;
    --color-accent: #9D0A12;
    --color-accent-light: #fdf2f3;
    --color-bg: #fafbfc;
    --color-surface: #ffffff;
    --color-surface-elevated: #ffffff;
    --color-border: #e2e8f0;
    --color-border-light: #f1f5f9;
    --color-text-primary: #0f172a;
    --color-text-secondary: #475569;
    --color-text-tertiary: #94a3b8;
    --color-text-inverse: #ffffff;
    --color-success: #059669;
    --color-success-light: #ecfdf5;
    --color-warning: #d97706;
    --color-warning-light: #fffbeb;

    --font-display: 'Noto Serif SC', 'STSong', 'SimSun', serif;
    --font-body: 'Noto Sans SC', 'PingFang SC', 'Microsoft YaHei', sans-serif;

    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.03);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.05), 0 2px 4px -1px rgba(0, 0, 0, 0.03);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.06), 0 4px 6px -2px rgba(0, 0, 0, 0.03);
    --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.08), 0 10px 10px -5px rgba(0, 0, 0, 0.03);
    --shadow-card: 0 1px 3px 0 rgba(0, 0, 0, 0.04), 0 1px 2px -1px rgba(0, 0, 0, 0.03);
    --shadow-card-hover: 0 8px 20px -4px rgba(0, 0, 0, 0.08), 0 2px 6px -2px rgba(0, 0, 0, 0.04);

    --radius-sm: 6px;
    --radius-md: 10px;
    --radius-lg: 16px;
    --radius-xl: 24px;

    --transition-fast: 150ms ease;
    --transition-base: 250ms ease;
    --transition-slow: 350ms ease;

    --sidebar-width: 280px;
    --header-height: 64px;
    --footer-height: 80px;
    --ai-width: 460px;
    --ai-width-wide: 560px;
}

*, *::before, *::after {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

html {
    font-size: 16px;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

body {
    font-family: var(--font-body);
    font-size: 0.9375rem;
    line-height: 1.7;
    color: var(--color-text-primary);
    background-color: var(--color-bg);
    min-height: 100vh;
}

h1, h2, h3, h4, h5, h6 {
    font-family: var(--font-display);
    font-weight: 600;
    line-height: 1.3;
    color: var(--color-text-primary);
}

a {
    color: var(--color-primary);
    text-decoration: none;
    transition: color var(--transition-fast);
}

a:hover {
    color: var(--color-primary-dark);
}

button {
    font-family: inherit;
    cursor: pointer;
    border: none;
    background: none;
}

input, select, textarea {
    font-family: inherit;
    font-size: inherit;
}

.screen {
    display: none;
}

.screen.active {
    display: flex;
    flex-direction: column;
    position: fixed;
    inset: 0;
    z-index: 1000;
    overflow-y: auto;
    background: var(--color-bg);
}

.hidden {
    display: none !important;
}


.onboarding-container {
    width: 100%;
    max-width: 1680px;
    margin: 0 auto;
    padding: 48px clamp(24px, 5vw, 80px);
    display: flex;
    flex-direction: column;
    gap: 40px;
}

/* 登录/注册表单保持窄居中，不随欢迎页一起撑宽 */
#onboarding-auth {
    width: 100%;
    max-width: 600px;
    margin: 0 auto;
}

.onboarding-hero {
    text-align: center;
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 20px;
}

.logo-mark {
    width: 80px;
    height: 80px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: linear-gradient(135deg, var(--color-primary-light) 0%, #ffffff 100%);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-md);
}

.logo-mark svg {
    width: 48px;
    height: 48px;
}

.onboarding-title {
    font-size: 1.875rem;
    font-weight: 700;
    color: var(--color-text-primary);
    letter-spacing: -0.02em;
}

.onboarding-subtitle {
    font-size: 1rem;
    color: var(--color-text-secondary);
    max-width: 400px;
    line-height: 1.6;
}

/* ==================== Welcome / Feature Showcase ==================== */

.welcome-section {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 100px;
    padding: 0 0 80px;
    position: relative;
    scroll-behavior: smooth;
}

/* ==================== STICKY ANCHOR NAV ==================== */
.welcome-nav {
    position: sticky;
    top: 0;
    z-index: 50;
    width: 100%;
    margin-bottom: -64px; /* 抵消 welcome-section 的 100px gap，使其下方留白合理 */
    background: rgba(255,255,255,0.72);
    backdrop-filter: blur(14px);
    -webkit-backdrop-filter: blur(14px);
    border-bottom: 1px solid rgba(0,78,161,0.10);
    box-shadow: 0 1px 0 rgba(255,255,255,0.6) inset, 0 4px 20px rgba(0,78,161,0.04);
}
.welcome-nav-inner {
    max-width: none;
    margin: 0 auto;
    padding: 12px 20px;
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 16px;
}
.welcome-nav-brand {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    font-family: var(--font-display, sans-serif);
    font-weight: 800;
    font-size: 1.05rem;
    color: #0a1628;
    letter-spacing: -0.01em;
    cursor: pointer;
    flex-shrink: 0;
}
.welcome-nav-links {
    display: flex;
    align-items: center;
    gap: 4px;
    overflow-x: auto;
    scrollbar-width: none;
}
.welcome-nav-links::-webkit-scrollbar { display: none; }
.welcome-nav-link {
    padding: 7px 14px;
    border-radius: 100px;
    font-size: 0.875rem;
    font-weight: 600;
    color: var(--color-text-secondary, #475569);
    white-space: nowrap;
    cursor: pointer;
    transition: color 0.2s ease, background 0.2s ease;
}
.welcome-nav-link:hover {
    color: var(--color-primary, #004EA1);
    background: rgba(0,78,161,0.06);
}
.welcome-nav-link.active {
    color: var(--color-primary, #004EA1);
    background: rgba(0,78,161,0.09);
}
.welcome-nav-cta {
    color: #fff !important;
    background: linear-gradient(135deg, var(--color-primary) 0%, #0070d6 100%);
    box-shadow: 0 2px 10px rgba(0,78,161,0.28);
}
.welcome-nav-cta:hover {
    background: linear-gradient(135deg, #003a7a 0%, #005bb8 100%) !important;
    color: #fff !important;
}

/* 锚点目标避开吸顶导航 */
#w-hero, #w-features, #w-compare, #w-details, #w-cta {
    scroll-margin-top: 76px;
}

@media (max-width: 600px) {
    .welcome-nav-brand span { display: none; }
    .welcome-nav-inner { padding: 10px 14px; }
    .welcome-nav-link { padding: 6px 11px; font-size: 0.82rem; }
}

/* ==================== BACKGROUND ==================== */
.welcome-bg {
    position: absolute;
    inset: 0;
    pointer-events: none;
    overflow: hidden;
}

/* Hexagonal lattice pattern */
.welcome-bg-hex {
    position: absolute;
    inset: -10%;
    background-image:
        url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='60' height='52' viewBox='0 0 60 52'%3E%3Cpath d='M30 0L60 15v22L30 52 0 37V15z' fill='none' stroke='%23004EA1' stroke-width='0.5' opacity='0.06'/%3E%3C/svg%3E");
    background-size: 60px 52px;
    mask-image: radial-gradient(ellipse 70% 50% at 50% 35%, black 25%, transparent 70%);
    -webkit-mask-image: radial-gradient(ellipse 70% 50% at 50% 35%, black 25%, transparent 70%);
}

/* Subtle noise texture overlay */
.welcome-bg-noise {
    position: absolute;
    inset: 0;
    opacity: 0.025;
    background-image: url("data:image/svg+xml,%3Csvg viewBox='0 0 256 256' xmlns='http://www.w3.org/2000/svg'%3E%3Cfilter id='n'%3E%3CfeTurbulence type='fractalNoise' baseFrequency='0.65' numOctaves='3' stitchTiles='stitch'/%3E%3C/filter%3E%3Crect width='100%25' height='100%25' filter='url(%23n)'/%3E%3C/svg%3E");
    background-size: 256px 256px;
}

/* Floating crystal shapes */
.welcome-bg-crystal {
    position: absolute;
    border-radius: 4px;
    opacity: 0.08;
    animation: crystal-drift 20s ease-in-out infinite;
}

.welcome-bg-crystal-1 {
    width: 110px; height: 110px;
    background: var(--color-primary);
    clip-path: polygon(50% 0%, 100% 25%, 100% 75%, 50% 100%, 0% 75%, 0% 25%);
    top: 15%; right: 8%;
    animation-delay: 0s;
}

.welcome-bg-crystal-2 {
    width: 70px; height: 70px;
    background: var(--color-accent);
    clip-path: polygon(50% 0%, 100% 38%, 82% 100%, 18% 100%, 0% 38%);
    bottom: 30%; left: 5%;
    animation-delay: -7s;
}

.welcome-bg-crystal-3 {
    width: 55px; height: 55px;
    background: #0d9488;
    clip-path: polygon(25% 0%, 75% 0%, 100% 50%, 75% 100%, 25% 100%, 0% 50%);
    top: 45%; right: 15%;
    animation-delay: -14s;
}

@keyframes crystal-drift {
    0%, 100% { transform: translate(0, 0) rotate(0deg); }
    25% { transform: translate(15px, -20px) rotate(5deg); }
    50% { transform: translate(-10px, -8px) rotate(-3deg); }
    75% { transform: translate(-18px, 12px) rotate(7deg); }
}

/* Ambient light orbs */
.welcome-bg-orb {
    position: absolute;
    border-radius: 50%;
    filter: blur(100px);
    opacity: 0.35;
    animation: orb-float 14s ease-in-out infinite;
}

.welcome-bg-orb-1 {
    width: 600px; height: 600px;
    background: radial-gradient(circle, rgba(0,78,161,0.15) 0%, transparent 70%);
    top: -180px; right: -150px;
    animation-delay: 0s;
}

.welcome-bg-orb-2 {
    width: 450px; height: 450px;
    background: radial-gradient(circle, rgba(157,10,18,0.09) 0%, transparent 70%);
    bottom: 12%; left: -100px;
    animation-delay: -5s;
}

.welcome-bg-orb-3 {
    width: 380px; height: 380px;
    background: radial-gradient(circle, rgba(13,148,136,0.10) 0%, transparent 70%);
    top: 45%; right: 8%;
    animation-delay: -10s;
}

@keyframes orb-float {
    0%, 100% { transform: translate(0, 0) scale(1); }
    25% { transform: translate(30px, -40px) scale(1.06); }
    50% { transform: translate(-15px, -20px) scale(0.94); }
    75% { transform: translate(-25px, 30px) scale(1.03); }
}

/* ==================== HERO ==================== */
.welcome-hero {
    text-align: center;
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 24px;
    position: relative;
    z-index: 1;
    padding-top: 72px;
}

.welcome-hero-badge {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    padding: 7px 18px;
    background: rgba(0,78,161,0.06);
    border: 1px solid rgba(0,78,161,0.12);
    border-radius: 100px;
    font-size: 0.875rem;
    font-weight: 500;
    color: var(--color-primary);
    backdrop-filter: blur(8px);
    -webkit-backdrop-filter: blur(8px);
}

.welcome-hero-badge-dot {
    width: 6px; height: 6px;
    border-radius: 50%;
    background: var(--color-primary);
    animation: pulse-dot 2s ease-in-out infinite;
}

@keyframes pulse-dot {
    0%, 100% { opacity: 1; transform: scale(1); }
    50% { opacity: 0.4; transform: scale(1.5); }
}

.welcome-title {
    font-family: var(--font-display);
    font-size: 4.25rem;
    font-weight: 800;
    color: #0a1628;
    letter-spacing: -0.04em;
    line-height: 1.2;
    max-width: 920px;
}

.welcome-title-highlight {
    background: linear-gradient(135deg, var(--color-primary) 0%, #2b7fd6 40%, var(--color-accent) 100%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    position: relative;
}

/* Decorative underline accent */
.welcome-hero::after {
    content: '';
    width: 80px;
    height: 5px;
    background: linear-gradient(90deg, var(--color-primary), var(--color-accent));
    border-radius: 2px;
    margin-top: 4px;
}

.welcome-tagline {
    font-size: 1.3rem;
    color: #475569;
    max-width: 640px;
    line-height: 1.9;
}

/* ==================== STATS ROW ==================== */
.welcome-stats {
    display: flex;
    align-items: center;
    gap: 64px;
    padding: 36px 72px;
    max-width: 760px;
    width: 100%;
    justify-content: center;
    background: rgba(255,255,255,0.7);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    border: 1px solid rgba(0,78,161,0.08);
    border-radius: var(--radius-xl);
    position: relative;
    z-index: 1;
    box-shadow: 0 1px 3px rgba(0,0,0,0.03), 0 8px 24px rgba(0,78,161,0.04);
}

.welcome-stat {
    text-align: center;
    display: flex;
    flex-direction: column;
    gap: 2px;
    flex: 1;
    min-width: 0;
}

.welcome-stat-number {
    font-family: 'SF Mono', 'Menlo', 'Consolas', monospace;
    font-size: 2.5rem;
    font-weight: 800;
    background: linear-gradient(180deg, var(--color-primary) 0%, #003a7a 100%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    letter-spacing: -0.04em;
    line-height: 1;
}

.welcome-stat-label {
    font-size: 0.9375rem;
    color: var(--color-text-secondary);
    font-weight: 600;
    margin-top: 2px;
}

.welcome-stat-desc {
    font-size: 0.8125rem;
    color: var(--color-text-tertiary);
    margin-top: 2px;
    line-height: 1.4;
}

.welcome-stat-divider {
    width: 1px;
    height: 56px;
    background: linear-gradient(180deg, transparent, rgba(0,78,161,0.12), transparent);
}

/* ==================== SECTION LABEL ==================== */
.welcome-section-label {
    font-family: var(--font-display);
    font-size: 1.5rem;
    font-weight: 700;
    color: #0a1628;
    text-align: center;
    position: relative;
    z-index: 1;
    letter-spacing: -0.01em;
}

.welcome-section-label::after {
    content: '';
    display: block;
    width: 48px;
    height: 3px;
    background: linear-gradient(90deg, var(--color-primary), var(--color-accent));
    border-radius: 2px;
    margin: 10px auto 0;
}

/* ==================== FEATURE CARDS ==================== */
.welcome-features {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 20px;
    width: 100%;
    position: relative;
    z-index: 1;
}

.welcome-feature-card {
    background: rgba(255,255,255,0.75);
    backdrop-filter: blur(8px);
    -webkit-backdrop-filter: blur(8px);
    border: 1px solid rgba(0,78,161,0.08);
    border-radius: var(--radius-lg);
    padding: 28px 30px;
    display: flex;
    align-items: center;
    gap: 14px;
    transition: all 0.4s cubic-bezier(0.22, 0.61, 0.36, 1);
    cursor: pointer;
    position: relative;
    overflow: hidden;
    animation: card-rise 0.6s cubic-bezier(0.22, 0.61, 0.36, 1) both;
    animation-delay: calc(var(--delay, 0) * 0.07s);
}

@keyframes card-rise {
    from { opacity: 0; transform: translateY(24px); }
    to { opacity: 1; transform: translateY(0); }
}

/* Subtle inner glow on hover */
.welcome-feature-card::after {
    content: '';
    position: absolute;
    inset: 0;
    background: radial-gradient(ellipse at center, rgba(0,78,161,0.03) 0%, transparent 70%);
    opacity: 0;
    transition: opacity 0.4s ease;
}

.welcome-feature-card:hover {
    border-color: rgba(0,78,161,0.2);
    box-shadow: 0 4px 24px rgba(0,78,161,0.08), 0 1px 4px rgba(0,0,0,0.04);
    transform: translateY(-3px);
    background: rgba(255,255,255,0.95);
}

.welcome-feature-card:hover::after {
    opacity: 1;
}

.welcome-feature-card:hover .welcome-feature-arrow {
    opacity: 1;
    transform: translateX(0);
}

.welcome-feature-icon {
    width: 52px;
    height: 52px;
    min-width: 52px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: rgba(0,78,161,0.06);
    border-radius: var(--radius-md);
    color: var(--color-primary);
    position: relative;
    z-index: 1;
    transition: all 0.4s ease;
}

.welcome-feature-card:hover .welcome-feature-icon {
    background: var(--color-primary-light);
    box-shadow: 0 0 0 4px rgba(0,78,161,0.06);
}

.welcome-feature-card:nth-child(even) .welcome-feature-icon {
    background: rgba(157,10,18,0.05);
    color: var(--color-accent);
}

.welcome-feature-card:nth-child(even):hover .welcome-feature-icon {
    background: var(--color-accent-light);
    box-shadow: 0 0 0 4px rgba(157,10,18,0.05);
}

.welcome-feature-icon svg {
    width: 24px;
    height: 24px;
}

.welcome-feature-text {
    flex: 1;
    min-width: 0;
    position: relative;
    z-index: 1;
}

.welcome-feature-text h3 {
    font-family: var(--font-body);
    font-size: 0.9375rem;
    font-weight: 600;
    color: #0a1628;
    margin: 0 0 4px;
}

.welcome-feature-text p {
    font-size: 0.8125rem;
    color: var(--color-text-secondary);
    margin: 0;
    line-height: 1.5;
}

.welcome-feature-arrow {
    font-size: 1.1rem;
    color: var(--color-primary);
    opacity: 0;
    transform: translateX(-8px);
    transition: all 0.4s cubic-bezier(0.22, 0.61, 0.36, 1);
    position: relative;
    z-index: 1;
}

/* ==================== COMPARISON ==================== */
.welcome-compare {
    display: flex;
    align-items: stretch;
    gap: 0;
    max-width: none;
    width: 100%;
    position: relative;
    z-index: 1;
}

.welcome-compare-card {
    flex: 1;
    padding: 40px 36px;
    border-radius: var(--radius-lg);
    display: flex;
    flex-direction: column;
    gap: 18px;
}

.welcome-compare-old {
    background: #f1f5f9;
    border: 1px solid #e2e8f0;
}

.welcome-compare-new {
    background: linear-gradient(135deg, rgba(0,78,161,0.03), rgba(0,78,161,0.01));
    border: 1px solid rgba(0,78,161,0.15);
    position: relative;
}

.welcome-compare-new::before {
    content: '推荐';
    position: absolute;
    top: -10px;
    right: 24px;
    background: var(--color-primary);
    color: white;
    font-size: 0.6875rem;
    font-weight: 600;
    padding: 3px 12px;
    border-radius: 100px;
    letter-spacing: 0.03em;
}

.welcome-compare-header {
    display: flex;
    align-items: center;
    gap: 10px;
    font-weight: 600;
    font-size: 1rem;
}

.welcome-compare-old .welcome-compare-header { color: #64748b; }
.welcome-compare-new .welcome-compare-header { color: var(--color-primary); }

.welcome-compare-header svg {
    width: 22px;
    height: 22px;
    opacity: 0.7;
}

.welcome-compare-old .welcome-compare-header svg { color: #94a3b8; }
.welcome-compare-new .welcome-compare-header svg { color: var(--color-primary); }

.welcome-compare-card ul {
    list-style: none;
    padding: 0;
    margin: 0;
    display: flex;
    flex-direction: column;
    gap: 12px;
}

.welcome-compare-card li {
    font-size: 0.875rem;
    padding-left: 22px;
    position: relative;
    line-height: 1.6;
}

.welcome-compare-old li { color: #64748b; }
.welcome-compare-old li::before {
    content: '\00D7';
    position: absolute;
    left: 0;
    color: #94a3b8;
    font-weight: 700;
    font-size: 0.875rem;
}

.welcome-compare-new li { color: #334155; }
.welcome-compare-new li::before {
    content: '\2713';
    position: absolute;
    left: 0;
    color: var(--color-success);
    font-weight: 700;
    font-size: 0.875rem;
}

.welcome-compare-vs {
    display: flex;
    align-items: center;
    justify-content: center;
    width: 56px;
    min-width: 56px;
}

.welcome-compare-vs-inner {
    width: 36px;
    height: 36px;
    border-radius: 50%;
    background: white;
    border: 2px solid #e2e8f0;
    display: flex;
    align-items: center;
    justify-content: center;
    font-family: var(--font-display);
    font-weight: 700;
    font-size: 0.6875rem;
    color: #94a3b8;
    letter-spacing: 0.05em;
    box-shadow: 0 2px 8px rgba(0,0,0,0.04);
}

/* ==================== Frontier + Grounding ==================== */
.welcome-grounding {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 20px;
    position: relative;
    z-index: 1;
}

.welcome-grounding-card {
    background: white;
    border: 1px solid #e8edf3;
    border-radius: 16px;
    padding: 28px 28px 24px;
    box-shadow: 0 2px 12px rgba(0,0,0,0.03);
    transition: transform 0.25s ease, box-shadow 0.25s ease;
}

.welcome-grounding-card:hover {
    transform: translateY(-3px);
    box-shadow: 0 12px 28px rgba(0,78,161,0.08);
}

.welcome-grounding-icon {
    width: 46px;
    height: 46px;
    border-radius: 12px;
    background: var(--color-primary-light);
    color: var(--color-primary);
    display: flex;
    align-items: center;
    justify-content: center;
    margin-bottom: 16px;
}

.welcome-grounding-card:nth-child(even) .welcome-grounding-icon {
    background: var(--color-accent-light);
    color: var(--color-accent);
}

.welcome-grounding-icon svg { width: 24px; height: 24px; }

.welcome-grounding-card h3 {
    font-family: var(--font-display);
    font-size: 1.25rem;
    font-weight: 700;
    color: #0a1628;
    margin: 0 0 10px;
    letter-spacing: -0.01em;
}

.welcome-grounding-card p {
    font-size: 0.9375rem;
    line-height: 1.7;
    color: #475569;
    margin: 0 0 18px;
}

.welcome-grounding-card p strong { color: #1e293b; font-weight: 600; }

.welcome-grounding-tags {
    display: flex;
    flex-wrap: wrap;
    gap: 8px;
}

.welcome-grounding-tag {
    font-size: 0.75rem;
    font-weight: 600;
    padding: 5px 11px;
    border-radius: 999px;
    background: #f1f5f9;
    color: #64748b;
}

.welcome-grounding-tag-book { background: rgba(0,78,161,0.08); color: var(--color-primary); }
.welcome-grounding-tag-paper { background: rgba(157,10,18,0.08); color: var(--color-accent); }

.welcome-stat-plus { font-size: 0.6em; vertical-align: super; opacity: 0.7; }

@media (max-width: 720px) {
    .welcome-grounding { grid-template-columns: 1fr; }
}

/* ==================== CTA ==================== */
.welcome-cta-section {
    text-align: center;
    position: relative;
    z-index: 1;
    padding: 32px 0 8px;
}

.welcome-cta-section h2 {
    font-family: var(--font-display);
    font-size: 2.25rem;
    font-weight: 700;
    color: #0a1628;
    margin: 0 0 16px;
    letter-spacing: -0.02em;
}

.welcome-cta-section p {
    font-size: 1.125rem;
    color: var(--color-text-secondary);
    margin: 0 0 32px;
}

.welcome-cta {
    display: inline-flex;
    align-items: center;
    gap: 10px;
    padding: 22px 64px;
    background: linear-gradient(135deg, var(--color-primary) 0%, #0066d6 100%);
    color: #fff;
    font-size: 1.25rem;
    font-weight: 600;
    border: none;
    border-radius: var(--radius-xl);
    cursor: pointer;
    transition: all 0.3s cubic-bezier(0.22, 0.61, 0.36, 1);
    box-shadow: 0 4px 24px rgba(0,78,161,0.35), 0 0 0 1px rgba(0,78,161,0.1);
    position: relative;
}

/* Animated pulse ring */
.welcome-cta::before {
    content: '';
    position: absolute;
    inset: -6px;
    border-radius: calc(var(--radius-xl) + 6px);
    border: 2px solid rgba(0,78,161,0.2);
    animation: cta-pulse 2.5s ease-out infinite;
}

@keyframes cta-pulse {
    0% { transform: scale(1); opacity: 0.6; }
    100% { transform: scale(1.08); opacity: 0; }
}

.welcome-cta:hover {
    transform: translateY(-3px);
    box-shadow: 0 8px 36px rgba(0,78,161,0.45), 0 0 0 2px rgba(0,78,161,0.15);
}

.welcome-cta:active {
    transform: translateY(-1px);
}

.welcome-cta svg {
    transition: transform 0.3s ease;
}

.welcome-cta:hover svg {
    transform: translateX(3px);
}

.welcome-footer-note {
    font-size: 0.875rem;
    color: var(--color-text-tertiary);
    margin-top: 20px;
}

.welcome-footer-note a {
    color: var(--color-primary);
    font-weight: 600;
    transition: color 0.2s ease;
}

.welcome-footer-note a:hover {
    color: var(--color-primary-dark);
}

.welcome-section.hidden {
    display: none;
}

/* ==================== DETAIL SECTIONS ==================== */
.welcome-details {
    display: flex;
    flex-direction: column;
    gap: 36px;
    max-width: none;
    width: 100%;
    position: relative;
    z-index: 1;
}

.welcome-detail {
    display: flex;
    gap: 32px;
    padding: 44px;
    background: rgba(255,255,255,0.8);
    backdrop-filter: blur(8px);
    -webkit-backdrop-filter: blur(8px);
    border: 1px solid rgba(0,78,161,0.06);
    border-radius: var(--radius-xl);
    opacity: 0;
    transform: translateY(32px);
    transition: opacity 0.6s cubic-bezier(0.22, 0.61, 0.36, 1),
                transform 0.6s cubic-bezier(0.22, 0.61, 0.36, 1),
                box-shadow 0.3s ease,
                border-color 0.3s ease;
}

.welcome-detail.revealed {
    opacity: 1;
    transform: translateY(0);
}

.welcome-detail:hover {
    border-color: rgba(0,78,161,0.15);
    box-shadow: 0 4px 24px rgba(0,78,161,0.06);
}

.welcome-detail-icon {
    width: 60px;
    height: 60px;
    min-width: 60px;
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: var(--radius-lg);
    transition: all 0.3s ease;
}

.welcome-detail:hover .welcome-detail-icon {
    box-shadow: 0 0 0 6px rgba(0,78,161,0.04);
}

.welcome-detail-icon svg {
    width: 28px;
    height: 28px;
}

.welcome-detail-body {
    flex: 1;
    min-width: 0;
}

.welcome-detail-body h3 {
    font-family: var(--font-display);
    font-size: 1.25rem;
    font-weight: 700;
    margin: 0 0 6px;
    color: #0a1628;
}

.welcome-detail-subtitle {
    font-size: 0.875rem;
    color: var(--color-text-secondary);
    margin: 0 0 22px;
}

.welcome-detail-content h4 {
    font-size: 0.875rem;
    font-weight: 600;
    color: var(--color-primary);
    margin: 18px 0 6px;
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

.welcome-detail-content h4:first-child {
    margin-top: 0;
}

.welcome-detail-content p {
    font-size: 0.9375rem;
    color: var(--color-text-secondary);
    line-height: 1.8;
    margin: 0;
}

.welcome-detail-content ul {
    margin: 6px 0 0;
    padding-left: 20px;
}

.welcome-detail-content li {
    font-size: 0.875rem;
    color: var(--color-text-secondary);
    margin-bottom: 6px;
    line-height: 1.7;
}

.welcome-detail-content li::marker {
    color: var(--color-primary);
}

.welcome-detail-content strong {
    color: #0a1628;
    font-weight: 600;
}

/* ==================== RESPONSIVE ==================== */
@media (max-width: 768px) {
    .welcome-features {
        grid-template-columns: repeat(2, 1fr);
    }
    .welcome-title {
        font-size: 2.75rem;
    }
    .welcome-tagline {
        font-size: 1.125rem;
    }
    .welcome-stats {
        gap: 36px;
        padding: 28px 40px;
    }
    .welcome-stat-number {
        font-size: 2.25rem;
    }
    .welcome-compare {
        flex-direction: column;
        gap: 16px;
    }
    .welcome-compare-vs {
        width: 100%;
        padding: 0;
    }
    .welcome-compare-vs-inner {
        width: 32px;
        height: 32px;
    }
    .welcome-compare-new::before {
        right: 16px;
    }
    .welcome-detail {
        flex-direction: column;
        gap: 24px;
        padding: 32px;
    }
}

@media (max-width: 480px) {
    .welcome-features {
        grid-template-columns: 1fr;
    }
    .welcome-title {
        font-size: 2.25rem;
    }
    .welcome-section {
        gap: 60px;
    }
    .welcome-stats {
        gap: 20px;
        padding: 22px 24px;
        flex-wrap: wrap;
    }
    .welcome-stat-divider {
        height: 40px;
    }
    .welcome-cta-section h2 {
        font-size: 1.25rem;
    }
    .welcome-cta {
        padding: 16px 40px;
        font-size: 1rem;
    }
    .welcome-detail {
        padding: 24px;
    }
}

/* ==================== Profile Card ==================== */


.profile-setup-card {
    background: var(--color-surface);
    border-radius: var(--radius-xl);
    padding: 40px;
    box-shadow: var(--shadow-lg);
    border: 1px solid var(--color-border-light);
}

.profile-setup-card:hover {
    box-shadow: var(--shadow-xl);
}

.card-title {
    font-size: 1.25rem;
    font-weight: 600;
    margin-bottom: 8px;
}

.card-description {
    font-size: 0.875rem;
    color: var(--color-text-secondary);
    margin-bottom: 32px;
}

.profile-form {
    display: flex;
    flex-direction: column;
    gap: 24px;
}

.form-group {
    display: flex;
    flex-direction: column;
    gap: 8px;
}

/* ① 简历/成绩上传 */
.profile-upload-btn {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    align-self: flex-start;
    padding: 9px 16px;
    border: 1.5px dashed var(--color-primary);
    border-radius: var(--radius-md);
    background: rgba(0,78,161,0.05);
    color: var(--color-primary);
    font-size: 0.9rem;
    font-weight: 600;
    font-family: var(--font-body);
    cursor: pointer;
    transition: background .15s ease;
}
.profile-upload-btn:hover { background: rgba(0,78,161,0.1); }
.profile-upload-hint {
    font-size: 0.8rem;
    color: var(--color-text-secondary);
    line-height: 1.5;
}
.profile-upload-list {
    display: flex;
    flex-direction: column;
    gap: 6px;
}
.profile-upload-list:empty { display: none; }
.profile-file-row {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 10px;
    padding: 7px 12px;
    background: var(--color-bg);
    border: 1px solid var(--color-border-light);
    border-radius: 8px;
    font-size: 0.82rem;
}
.profile-file-name { color: var(--color-text-primary); overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
.profile-file-status { flex: 0 0 auto; color: var(--color-text-secondary); }
.profile-file-status.ok { color: var(--color-success, #16a34a); }
.profile-file-status.warn { color: #d97706; }
.profile-file-status.err { color: var(--color-accent); }
.profile-distill {
    font-size: 0.82rem;
    color: var(--color-text-secondary);
    padding: 6px 2px;
}
.profile-distill.ok { color: var(--color-success, #16a34a); }
.profile-distill.err { color: var(--color-accent); }

.form-group label {
    font-size: 0.875rem;
    font-weight: 500;
    color: var(--color-text-primary);
}

.form-group input[type="text"],
.form-group input[type="email"],
.form-group input[type="password"],
.form-group input[type="number"],
.form-group select,
.form-group textarea {
    padding: 12px 16px;
    border: 1.5px solid var(--color-border);
    border-radius: var(--radius-md);
    font-size: 0.9375rem;
    font-family: var(--font-body);
    transition: border-color var(--transition-fast), box-shadow var(--transition-fast);
    background: var(--color-surface);
    color: var(--color-text-primary);
}

.form-group input[type="text"]:focus,
.form-group input[type="email"]:focus,
.form-group input[type="password"]:focus,
.form-group input[type="number"]:focus,
.form-group select:focus,
.form-group textarea:focus {
    outline: none;
    border-color: var(--color-primary);
    box-shadow: 0 0 0 3px rgba(0, 78, 161, 0.08), var(--shadow-sm);
}

.form-group input::placeholder {
    color: var(--color-text-tertiary);
}

.radio-group,
.checkbox-group {
    display: flex;
    flex-wrap: wrap;
    gap: 10px;
}

.radio-option,
.checkbox-option {
    display: flex;
    align-items: center;
    gap: 8px;
    padding: 10px 16px;
    border: 1.5px solid var(--color-border);
    border-radius: var(--radius-md);
    cursor: pointer;
    transition: all var(--transition-fast);
    background: var(--color-surface);
    flex: 1;
    min-width: 140px;
}

.radio-option:hover,
.checkbox-option:hover {
    border-color: var(--color-primary);
    background: var(--color-primary-light);
    transform: translateY(-1px);
    box-shadow: var(--shadow-sm);
}

.radio-option:has(input:checked),
.checkbox-option:has(input:checked) {
    border-color: var(--color-primary);
    background: var(--color-primary-light);
    box-shadow: 0 0 0 1px rgba(0, 78, 161, 0.1);
}

.radio-option input,
.checkbox-option input {
    width: 18px;
    height: 18px;
    accent-color: var(--color-primary);
    cursor: pointer;
    flex-shrink: 0;
}

.radio-label,
.checkbox-label {
    font-size: 0.875rem;
    color: var(--color-text-primary);
    cursor: pointer;
}


.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
    padding: 10px 20px;
    font-size: 0.875rem;
    font-weight: 500;
    border-radius: var(--radius-md);
    transition: all var(--transition-fast);
    cursor: pointer;
    border: 1.5px solid transparent;
    line-height: 1.4;
}

.btn:active {
    transform: scale(0.97);
}

.btn-primary {
    background: var(--color-primary);
    color: var(--color-text-inverse);
    border-color: var(--color-primary);
    box-shadow: 0 1px 2px rgba(0, 78, 161, 0.25);
}

.btn-primary:hover {
    background: var(--color-primary-dark);
    border-color: var(--color-primary-dark);
    color: var(--color-text-inverse);
    box-shadow: 0 2px 8px rgba(0, 78, 161, 0.3);
}

.btn-secondary {
    background: var(--color-surface);
    color: var(--color-text-primary);
    border-color: var(--color-border);
}

.btn-secondary:hover {
    background: var(--color-bg);
    border-color: var(--color-primary);
    color: var(--color-primary);
}

.btn-large {
    padding: 14px 28px;
    font-size: 1rem;
    font-weight: 600;
    border-radius: var(--radius-lg);
    width: 100%;
}

.btn-icon {
    display: flex;
    align-items: center;
    justify-content: center;
    width: 40px;
    height: 40px;
    border-radius: var(--radius-md);
    color: var(--color-text-secondary);
    transition: all var(--transition-fast);
    background: transparent;
}

.btn-icon:hover {
    background: var(--color-primary-light);
    color: var(--color-primary);
}

.btn-sm {
    padding: 6px 14px;
    font-size: 0.8125rem;
    font-weight: 500;
    border-radius: var(--radius-sm);
    border: none;
    cursor: pointer;
    transition: all var(--transition-fast);
}

.btn-cancel {
    padding: 6px 14px;
    font-size: 0.8125rem;
    font-weight: 500;
    border-radius: var(--radius-sm);
    border: 1px solid var(--color-border);
    background: var(--color-surface);
    color: var(--color-text-secondary);
    cursor: pointer;
    transition: all var(--transition-fast);
}

.btn-cancel:hover {
    background: var(--color-bg);
    color: var(--color-text-primary);
}


.app-container {
    display: grid;
    grid-template-areas:
        "header header"
        "sidebar main"
        "sidebar footer";
    grid-template-columns: var(--sidebar-width) 1fr;
    grid-template-rows: var(--header-height) 1fr auto;
    min-height: 100vh;
}

.app-header {
    grid-area: header;
    position: sticky;
    top: 0;
    z-index: 100;
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 0 24px;
    background: rgba(255, 255, 255, 0.85);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    border-bottom: 1px solid var(--color-border-light);
    height: var(--header-height);
    box-shadow: 0 1px 3px rgba(0, 0, 0, 0.02);
}

.header-left {
    display: flex;
    align-items: center;
    gap: 12px;
}

.header-logo {
    display: flex;
    align-items: center;
    gap: 10px;
    color: var(--color-text-primary);
    font-weight: 600;
    font-size: 1.0625rem;
}

.header-logo:hover {
    color: var(--color-primary);
}

.header-logo svg {
    color: var(--color-primary);
    flex-shrink: 0;
}

.logo-text {
    font-family: var(--font-display);
    font-weight: 700;
    letter-spacing: 0.02em;
}

.header-right {
    display: flex;
    align-items: center;
    gap: 12px;
}

.header-back-welcome {
    display: flex;
    align-items: center;
    gap: 4px;
    padding: 6px 12px;
    font-size: 0.8125rem;
    color: var(--color-text-tertiary);
    border-radius: var(--radius-md);
    transition: all var(--transition-fast);
    border: 1px solid transparent;
}

.header-back-welcome:hover {
    color: var(--color-primary);
    background: var(--color-primary-light);
    border-color: rgba(0, 78, 161, 0.1);
}

.header-back-welcome svg {
    flex-shrink: 0;
}

.progress-summary {
    display: flex;
    align-items: center;
    gap: 8px;
}

.progress-ring {
    position: relative;
    width: 32px;
    height: 32px;
}

.progress-ring svg {
    transform: rotate(-90deg);
}

.progress-ring-bg {
    fill: none;
    stroke: var(--color-border);
    stroke-width: 3;
}

.progress-ring-fill {
    fill: none;
    stroke: var(--color-primary);
    stroke-width: 3;
    stroke-linecap: round;
    transition: stroke-dasharray var(--transition-slow);
}

.progress-text {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    font-size: 0.625rem;
    font-weight: 600;
    color: var(--color-primary);
}

.user-avatar {
    color: var(--color-text-secondary);
    border-radius: 50%;
}

.user-avatar:hover {
    background: var(--color-primary-light);
    color: var(--color-primary);
}


.sidebar {
    grid-area: sidebar;
    position: sticky;
    top: var(--header-height);
    height: calc(100vh - var(--header-height));
    width: 100%;
    background: var(--color-surface);
    border-right: 1px solid var(--color-border-light);
    overflow-y: auto;
    overflow-x: hidden;
    z-index: 50;
    transition: transform var(--transition-base), width var(--transition-base);
}

/* 目录收起（桌面端）*/
@media (min-width: 1025px) {
    .app-container {
        transition: grid-template-columns var(--transition-base);
    }
    .app-container.toc-collapsed {
        grid-template-columns: 0 1fr;
        /* 目录收起后，AI 预留空间用更宽的值（main-content 的 padding 读取此变量）*/
        --ai-width: var(--ai-width-wide);
    }
    .app-container.toc-collapsed .sidebar {
        width: 0;
        overflow: hidden;
        border-right: none;
    }
    /* 目录收起时 AI 面板本体也加宽（面板在 #app 外部，用类驱动）*/
    .ai-sidebar.ai-wide {
        width: var(--ai-width-wide);
    }
}

.sidebar-nav {
    padding: 20px 0;
}

.nav-header {
    padding: 0 20px 16px;
    border-bottom: 1px solid var(--color-border-light);
    margin-bottom: 12px;
}

.nav-header h3 {
    font-size: 0.75rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.08em;
    color: var(--color-text-tertiary);
    font-family: var(--font-body);
}

.chapter-nav {
    display: flex;
    flex-direction: column;
}

.nav-part {
    border-bottom: 1px solid var(--color-border-light);
}

.nav-part-header {
    display: flex;
    align-items: center;
    gap: 10px;
    width: 100%;
    padding: 13px 16px;
    font-size: 0.8125rem;
    font-weight: 600;
    color: var(--color-text-primary);
    background: none;
    border: none;
    cursor: pointer;
    transition: all var(--transition-fast);
    text-align: left;
}

.nav-part-index {
    display: flex;
    align-items: center;
    justify-content: center;
    width: 20px;
    height: 20px;
    flex-shrink: 0;
    font-family: 'SF Mono', monospace;
    font-size: 0.7rem;
    font-weight: 700;
    color: var(--color-primary);
    background: var(--color-primary-light);
    border-radius: 6px;
}

.nav-part-title {
    flex: 1;
    min-width: 0;
}

.nav-part-count {
    font-size: 0.68rem;
    color: var(--color-text-tertiary);
    background: var(--color-bg);
    border-radius: 100px;
    padding: 1px 7px;
    flex-shrink: 0;
}

.nav-part-header:hover {
    background: var(--color-bg);
}

.nav-part-header.active {
    color: var(--color-primary);
}

.nav-part-toggle {
    display: flex;
    align-items: center;
    justify-content: center;
    width: 18px;
    height: 18px;
    color: var(--color-text-tertiary);
    transition: transform var(--transition-fast);
    flex-shrink: 0;
}

.nav-part.expanded .nav-part-toggle {
    transform: rotate(90deg);
}

.nav-chapters {
    display: none;
    flex-direction: column;
    padding: 4px 0;
}

.nav-part.expanded .nav-chapters {
    display: flex;
}

.nav-chapter {
    display: flex;
    align-items: center;
    gap: 9px;
    padding: 8px 16px 8px 18px;
    font-size: 0.85rem;
    color: var(--color-text-secondary);
    transition: all var(--transition-fast);
    position: relative;
    border-left: 2px solid transparent;
}

.nav-chapter:hover {
    background: var(--color-bg);
    color: var(--color-text-primary);
}

.nav-chapter.active {
    background: var(--color-primary-light);
    color: var(--color-primary);
    font-weight: 600;
    border-left-color: var(--color-primary);
}

.nav-chapter.completed .chapter-title::after {
    content: '✓';
    margin-left: 6px;
    color: #059669;
    font-weight: 700;
    font-size: 0.8em;
}

.nav-chapter .chapter-title {
    flex: 1;
    min-width: 0;
    overflow: hidden;
    text-overflow: ellipsis;
    white-space: nowrap;
}

.chapter-id {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    flex-shrink: 0;
    min-width: 38px;
    padding: 2px 6px;
    font-size: 0.68rem;
    font-weight: 600;
    color: var(--color-text-tertiary);
    background: var(--color-bg);
    border-radius: 5px;
    font-family: 'SF Mono', monospace;
}

.nav-chapter.active .chapter-id {
    background: rgba(0, 78, 161, 0.12);
    color: var(--color-primary);
}

.nav-chapter-row {
    display: flex;
    flex-direction: column;
}

.nav-chapter-row .nav-chapter {
    flex: 1;
}

.nav-chapter-quiz {
    display: block;
    padding: 1px 16px 6px 67px;
    font-size: 0.72rem;
    color: var(--color-text-tertiary);
    transition: color var(--transition-fast);
}

.nav-chapter-quiz:hover {
    color: var(--color-primary);
}

.sidebar-overlay {
    display: none;
}

/* ===== 侧边栏拖动手柄 ===== */
.resize-handle {
    position: absolute;
    top: 0;
    width: 7px;
    height: 100%;
    cursor: col-resize;
    z-index: 60;
}
.toc-resize-handle { right: -3px; }
.ai-resize-handle { left: -3px; }
.resize-handle::after {
    content: '';
    position: absolute;
    top: 0;
    bottom: 0;
    left: 50%;
    width: 2px;
    transform: translateX(-50%);
    background: transparent;
    transition: background var(--transition-fast);
}
.resize-handle:hover::after {
    background: var(--color-primary);
}
body.resizing {
    cursor: col-resize;
    user-select: none;
}
/* 拖动时隐藏目录手柄（收起态）*/
@media (max-width: 1024px) {
    .resize-handle { display: none; }
}


.main-content {
    grid-area: main;
    padding: 32px 40px;
    width: 100%;
}

/* 阅读区限宽居中，保证中文长文行长舒适 */
#view-chapter {
    max-width: 880px;
    margin-inline: auto;
}
/* 仪表盘（首页）居中，避免宽屏过度拉伸 */
#view-home {
    max-width: 1160px;
    margin-inline: auto;
}

/* AI 侧边打开时，为其预留空间（仅桌面端），正文不被遮挡 */
@media (min-width: 1024px) {
    .app-container.ai-open .main-content,
    .app-container.ai-open .app-footer {
        padding-right: calc(var(--ai-width) + 40px);
        transition: padding-right var(--transition-base);
    }
}

.page-header {
    margin-bottom: 36px;
}

.page-header h1 {
    font-size: 2.1rem;
    font-weight: 700;
    margin-bottom: 8px;
    letter-spacing: -0.01em;
    font-family: var(--font-display);
    line-height: 1.2;
}

.page-header h1::before {
    content: '';
    display: block;
    width: 48px;
    height: 4px;
    border-radius: 2px;
    background: linear-gradient(90deg, var(--color-primary), var(--color-accent));
    margin-bottom: 16px;
}

.page-subtitle {
    font-size: 1rem;
    color: var(--color-text-tertiary);
}

.continue-learning .btn {
    margin-top: 4px;
}

.continue-learning p {
    min-height: 2.4em;
}

/* Card icon color overrides */
.continue-learning .card-icon {
    color: var(--color-primary);
    background: var(--color-primary-light);
}

.progress-overview .card-icon {
    color: var(--color-success);
    background: var(--color-success-light);
}

.chapter-grid .card-icon {
    color: #d97706;
    background: #fffbeb;
}


.dashboard-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 20px;
}

.dashboard-card {
    background: var(--color-surface);
    border-radius: var(--radius-lg);
    padding: 28px;
    border: 1px solid var(--color-border-light);
    box-shadow: var(--shadow-card);
    transition: box-shadow var(--transition-base), transform var(--transition-base), border-color var(--transition-base);
    position: relative;
    overflow: hidden;
}

.dashboard-card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 3px;
    background: transparent;
    border-radius: var(--radius-lg) var(--radius-lg) 0 0;
    transition: background var(--transition-base);
}

.dashboard-card:hover {
    box-shadow: var(--shadow-card-hover);
    transform: translateY(-1px);
    border-color: var(--color-border);
}

.continue-learning::before { background: linear-gradient(90deg, var(--color-primary), #2575d0); }
.progress-overview::before { background: linear-gradient(90deg, var(--color-success), #14b8a6); }
.chapter-grid::before { background: linear-gradient(90deg, #f59e0b, #d97706); }
.ai-learning-path::before { background: linear-gradient(90deg, #7c3aed, #a78bfa); }
.mindmap-card::before { background: linear-gradient(90deg, #0d9488, #14b8a6); }
.wrong-answer-book::before { background: linear-gradient(90deg, var(--color-accent), #c41020); }

/* ⑤ 目标导向学习路径卡 */
.goal-card {
    margin-bottom: 20px;
    border-color: rgba(0,78,161,0.25);
}
.goal-card::before { background: linear-gradient(90deg, var(--color-primary), var(--color-accent)); }
.goal-card-head {
    display: flex;
    gap: 14px;
    align-items: flex-start;
}
.goal-card-icon {
    flex: 0 0 auto;
    width: 44px;
    height: 44px;
    border-radius: 12px;
    display: flex;
    align-items: center;
    justify-content: center;
    color: #fff;
    background: linear-gradient(135deg, var(--color-primary), #2575d0);
}
.goal-card-head h3 { margin: 0 0 4px; }
.goal-subtitle {
    margin: 0;
    font-size: 0.88rem;
    color: var(--color-text-secondary);
    line-height: 1.6;
}
.goal-subtitle strong { color: var(--color-primary); }
.goal-input-row {
    display: flex;
    gap: 10px;
    margin-top: 18px;
}
#goal-input {
    flex: 1;
    min-width: 0;
    padding: 11px 14px;
    border: 1px solid var(--color-border);
    border-radius: 10px;
    font-size: 0.92rem;
    font-family: var(--font-body);
    color: var(--color-text);
    outline: none;
    transition: border-color .15s ease, box-shadow .15s ease;
}
#goal-input:focus { border-color: var(--color-primary); box-shadow: 0 0 0 3px rgba(0,78,161,0.1); }
#goal-generate { flex: 0 0 auto; white-space: nowrap; }

.goal-path-result:empty { display: none; }
.goal-path-result { margin-top: 20px; }
.goal-loading, .goal-empty {
    font-size: 0.9rem;
    color: var(--color-text-secondary);
    padding: 8px 0;
}
.goal-result-head { margin-bottom: 16px; }
.goal-result-title {
    font-family: var(--font-display);
    font-size: 1.08rem;
    font-weight: 600;
    color: var(--color-text);
}
.goal-scope {
    margin: 6px 0 0;
    font-size: 0.86rem;
    color: var(--color-text-secondary);
    line-height: 1.6;
    padding: 8px 12px;
    background: var(--color-bg);
    border-left: 3px solid var(--color-primary);
    border-radius: 0 8px 8px 0;
}
.goal-steps {
    list-style: none;
    margin: 0;
    padding: 0;
    display: flex;
    flex-direction: column;
    gap: 12px;
}
.goal-step {
    display: flex;
    gap: 14px;
    padding: 16px;
    border: 1px solid var(--color-border-light);
    border-radius: 12px;
    background: var(--color-surface);
    position: relative;
}
.goal-step::before {
    content: '';
    position: absolute;
    left: 31px;
    top: 48px;
    bottom: -12px;
    width: 2px;
    background: var(--color-border);
}
.goal-step:last-child::before { display: none; }
.goal-step-no {
    flex: 0 0 auto;
    width: 32px;
    height: 32px;
    border-radius: 50%;
    background: linear-gradient(135deg, var(--color-primary), #2575d0);
    color: #fff;
    font-weight: 700;
    font-size: 0.92rem;
    display: flex;
    align-items: center;
    justify-content: center;
    z-index: 1;
}
.goal-step-body { flex: 1; min-width: 0; }
.goal-step-head {
    display: flex;
    align-items: baseline;
    gap: 8px;
    margin-bottom: 6px;
}
.goal-step-ch {
    flex: 0 0 auto;
    font-size: 0.74rem;
    font-weight: 600;
    color: var(--color-primary);
    background: rgba(0,78,161,0.08);
    padding: 1px 8px;
    border-radius: 999px;
}
.goal-step-title {
    font-family: var(--font-display);
    font-weight: 600;
    font-size: 0.98rem;
    color: var(--color-text);
}
.goal-step-line {
    margin: 4px 0 0;
    font-size: 0.86rem;
    line-height: 1.6;
    color: var(--color-text-secondary);
}
.goal-step-line strong { color: var(--color-text); font-weight: 600; }
.goal-step-go {
    margin-top: 10px;
    padding: 5px 12px;
    border: 1px solid var(--color-primary);
    border-radius: 8px;
    background: transparent;
    color: var(--color-primary);
    font-size: 0.82rem;
    font-weight: 600;
    cursor: pointer;
    transition: background .15s ease, color .15s ease;
}
.goal-step-go:hover { background: var(--color-primary); color: #fff; }
.goal-foot {
    margin: 14px 0 0;
    font-size: 0.78rem;
    color: var(--color-text-secondary);
    text-align: center;
}

.dashboard-card h3 {
    font-family: var(--font-display);
    font-size: 1.12rem;
    font-weight: 700;
    margin-bottom: 12px;
    color: var(--color-text-primary);
}

.dashboard-card p {
    font-size: 0.875rem;
    color: var(--color-text-secondary);
    margin-bottom: 16px;
}

.card-icon {
    width: 44px;
    height: 44px;
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: var(--radius-md);
    margin-bottom: 16px;
    color: var(--color-primary);
    background: var(--color-primary-light);
}

.card-icon svg {
    width: 22px;
    height: 22px;
}

.progress-bar {
    width: 100%;
    height: 8px;
    background: var(--color-border-light);
    border-radius: 4px;
    overflow: hidden;
    margin-bottom: 12px;
}

.progress-fill {
    height: 100%;
    background: linear-gradient(90deg, var(--color-primary) 0%, #2575d0 100%);
    border-radius: 4px;
    transition: width var(--transition-slow);
    position: relative;
}

.progress-fill::after {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: linear-gradient(180deg, rgba(255,255,255,0.25) 0%, transparent 100%);
    border-radius: 4px;
}

.quick-chapters {
    display: grid;
    grid-template-columns: 1fr;
    gap: 6px;
}

.quick-part-label {
    font-size: 0.6875rem;
    font-weight: 600;
    letter-spacing: 0.04em;
    padding: 6px 4px 2px 4px;
    font-family: var(--font-body);
    grid-column: 1 / -1;
}

.quick-part-label:first-child {
    padding-top: 0;
}

.quick-chapter-link {
    display: flex;
    align-items: center;
    gap: 8px;
    padding: 10px 12px;
    border-radius: var(--radius-md);
    font-size: 0.8125rem;
    color: var(--color-text-secondary);
    background: var(--color-bg);
    transition: all var(--transition-base);
    border: 1px solid var(--color-border-light);
    text-decoration: none;
}

.quick-chapter-link:hover {
    background: var(--color-primary-light);
    color: var(--color-primary);
    border-color: rgba(0, 78, 161, 0.15);
    transform: translateX(2px);
}

.quick-chapter-link .chapter-number {
    font-size: 0.6875rem;
    font-weight: 600;
    color: var(--part-color, var(--color-text-tertiary));
    min-width: 28px;
    font-family: 'SF Mono', monospace;
    transition: color var(--transition-fast);
}

.quick-chapter-link:hover .chapter-number {
    color: var(--color-primary);
}

.ai-learning-path {
    grid-column: 1 / -1;
}

.ai-learning-path .card-icon {
    color: #7c3aed;
    background: #f5f3ff;
}

.ai-path-subtitle {
    font-size: 0.8125rem;
    color: var(--color-text-tertiary);
    margin-bottom: 16px;
    margin-top: -8px;
}

.ai-path-loading {
    color: var(--color-text-tertiary) !important;
    font-style: italic;
}

.ai-path-result {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 14px;
}

.ai-path-section {
    padding: 18px 20px;
    background: var(--color-bg);
    border-radius: var(--radius-md);
    border: 1px solid var(--color-border-light);
    transition: all var(--transition-base);
}

.ai-path-section:hover {
    box-shadow: var(--shadow-card);
    transform: translateY(-1px);
}

.ai-path-section.full-width {
    grid-column: 1 / -1;
}

.ai-path-section.review {
    border-left: 3px solid var(--color-warning);
}

.ai-path-section.mastered {
    border-left: 3px solid var(--color-success);
}

.ai-path-section h4 {
    font-size: 0.875rem;
    font-weight: 600;
    color: var(--color-text-primary);
    margin-bottom: 8px;
}

.ai-path-section p {
    font-size: 0.875rem;
    color: var(--color-text-secondary);
    line-height: 1.7;
    margin-bottom: 0;
}

.ai-path-progress {
    grid-column: 1 / -1;
    background: var(--color-bg);
    border-radius: var(--radius-md);
    padding: 18px 20px;
    border: 1px solid var(--color-border-light);
}

.ai-path-progress-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    margin-bottom: 10px;
}

.ai-path-progress-header span {
    font-size: 0.875rem;
    font-weight: 600;
    color: var(--color-text-primary);
}

.ai-path-progress-header .progress-pct {
    font-weight: 700;
    color: #7c3aed;
    font-family: var(--font-mono);
}

.ai-path-mini-bar {
    height: 6px;
    background: var(--color-border-light);
    border-radius: 3px;
    overflow: hidden;
    margin-bottom: 10px;
}

.ai-path-mini-fill {
    height: 100%;
    background: linear-gradient(90deg, #7c3aed, #a78bfa);
    border-radius: 3px;
    transition: width var(--transition-slow);
}

.ai-path-stats-row {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 8px;
}

.ai-path-stat {
    text-align: center;
    padding: 10px 8px;
    background: var(--color-surface);
    border-radius: var(--radius-sm);
}

.ai-path-stat .stat-num {
    font-size: 1.25rem;
    font-weight: 700;
    color: #7c3aed;
    line-height: 1.1;
    font-family: var(--font-mono);
}

.ai-path-stat .stat-label {
    font-size: 0.7rem;
    color: var(--color-text-tertiary);
    margin-top: 3px;
}

.ai-path-empty-state {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    padding: 36px 24px;
    text-align: center;
    gap: 12px;
}

.ai-path-empty-state p {
    font-size: 0.9375rem;
    color: var(--color-text-secondary);
    margin: 0;
    max-width: 360px;
}

.ai-path-empty-hint {
    font-size: 0.8125rem !important;
    color: var(--color-text-tertiary) !important;
}

#refresh-ai-path {
    margin-top: 12px;
    display: inline-flex;
    align-items: center;
    gap: 6px;
}


.chapter-header {
    margin-bottom: 32px;
    padding-bottom: 24px;
    border-bottom: 1px solid var(--color-border);
}

.breadcrumb {
    display: flex;
    align-items: center;
    gap: 8px;
    font-size: 0.8125rem;
    color: var(--color-text-tertiary);
    margin-bottom: 16px;
}

.breadcrumb a {
    color: var(--color-text-secondary);
}

.breadcrumb a:hover {
    color: var(--color-primary);
}

.breadcrumb-separator {
    color: var(--color-border);
}

.chapter-header h1 {
    font-family: var(--font-display);
    font-size: 2.4rem;
    font-weight: 700;
    line-height: 1.25;
    margin-bottom: 12px;
    letter-spacing: -0.01em;
    color: var(--color-text-primary);
}

.chapter-header h1::before {
    content: '';
    display: block;
    width: 52px;
    height: 4px;
    border-radius: 2px;
    background: linear-gradient(90deg, var(--color-primary), var(--color-accent));
    margin-bottom: 18px;
}

.chapter-header p {
    font-size: 1.0625rem;
    color: var(--color-text-secondary);
    line-height: 1.7;
}

.chapter-content {
    min-height: 400px;
    margin-bottom: 40px;
    line-height: 1.85;
    font-size: 1.0rem;
    color: #1f2937;
}

.chapter-content h1 {
    font-family: var(--font-display);
    font-size: 1.9rem;
    font-weight: 700;
    margin: 8px 0 28px;
    color: var(--color-text-primary);
    letter-spacing: -0.01em;
}

.chapter-content h2 {
    font-family: var(--font-display);
    font-size: 1.55rem;
    font-weight: 700;
    margin-top: 48px;
    margin-bottom: 18px;
    padding: 0 0 12px 18px;
    color: var(--color-text-primary);
    border-bottom: 1px solid var(--color-border);
    position: relative;
}

.chapter-content h2::before {
    content: '';
    position: absolute;
    left: 0;
    top: 5px;
    bottom: 16px;
    width: 4px;
    border-radius: 2px;
    background: linear-gradient(180deg, var(--color-primary), var(--color-accent));
}

.chapter-content h3 {
    font-family: var(--font-display);
    font-size: 1.22rem;
    font-weight: 600;
    margin-top: 30px;
    margin-bottom: 12px;
    color: var(--color-primary);
}

.chapter-content p {
    margin-bottom: 18px;
    text-align: left;
}

.chapter-content strong {
    font-weight: 600;
    color: var(--color-text-primary);
}

.chapter-content a {
    color: var(--color-primary);
    text-decoration: underline;
    text-underline-offset: 2px;
    text-decoration-thickness: 1px;
}

.chapter-content blockquote {
    margin: 22px 0;
    padding: 4px 20px;
    border-left: 3px solid var(--color-primary);
    color: var(--color-text-secondary);
    font-style: italic;
    background: var(--color-primary-light);
    border-radius: 0 10px 10px 0;
}

.chapter-content table {
    width: 100%;
    border-collapse: collapse;
    margin: 24px 0;
    font-size: 0.9rem;
    border: 1px solid var(--color-border);
    border-radius: 10px;
    overflow: hidden;
    box-shadow: var(--shadow-card);
}

.chapter-content th,
.chapter-content td {
    padding: 12px 16px;
    text-align: left;
    border-bottom: 1px solid var(--color-border);
}

.chapter-content th {
    background: var(--color-primary-light);
    font-weight: 600;
    color: var(--color-primary);
    font-family: var(--font-display);
    letter-spacing: 0.01em;
}

.chapter-content tbody tr:nth-child(even) {
    background: var(--color-bg);
}

.chapter-content tbody tr:hover {
    background: var(--color-primary-light);
}

.chapter-content tr:last-child td {
    border-bottom: none;
}

.chapter-content ul,
.chapter-content ol {
    margin: 16px 0;
    padding-left: 24px;
}

.chapter-content li {
    margin-bottom: 8px;
}

.chapter-content .key-insight {
    background: linear-gradient(to bottom, transparent 55%, rgba(157, 10, 18, 0.10) 55%);
    padding: 0 3px;
    font-weight: 500;
}

.chapter-content .chapter-summary {
    background: linear-gradient(135deg, var(--color-primary-light), rgba(0, 78, 161, 0.03));
    border: 1px solid rgba(0, 78, 161, 0.12);
    border-left: 4px solid var(--color-primary);
    border-radius: 0 var(--radius-lg) var(--radius-lg) 0;
    padding: 24px 28px;
    margin: 32px 0;
    box-shadow: var(--shadow-sm);
}

.chapter-content .summary-title {
    font-family: var(--font-display);
    font-weight: 700;
    font-size: 1.1rem;
    color: var(--color-primary);
    margin-bottom: 14px;
    text-align: left;
    display: flex;
    align-items: center;
    gap: 8px;
}

.chapter-content .summary-title::before {
    content: '§';
    font-size: 1.2em;
    opacity: 0.5;
}

.chapter-content .figure-caption {
    font-style: italic;
}

.chapter-content .figure {
    margin: 24px 0;
    text-align: center;
}

.chapter-content .figure img {
    max-width: 100%;
    height: auto;
}

.chapter-content .figure-caption {
    font-size: 0.875rem;
    color: var(--color-text-secondary);
    margin-top: 8px;
}

.chapter-content .figure-label {
    font-weight: 700;
    color: var(--color-primary);
}

.content-loading,
.content-error {
    text-align: center;
    padding: 40px;
    color: var(--color-text-secondary);
    font-size: 1rem;
}

.content-error {
    color: var(--color-accent);
}

.chapter-nav-footer {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 16px;
    padding-top: 24px;
    border-top: 1px solid var(--color-border);
}

.chapter-nav-btn {
    display: inline-flex;
    align-items: center;
    gap: 8px;
}

.chapter-nav-btn.hidden {
    visibility: hidden;
}


.app-footer {
    grid-area: footer;
    background: var(--color-surface);
    border-top: 1px solid var(--color-border);
    padding: 24px 40px;
}

.footer-content {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 8px;
    text-align: center;
}

.footer-brand {
    display: flex;
    align-items: center;
    gap: 10px;
    font-weight: 600;
    color: var(--color-text-primary);
    font-size: 0.9375rem;
}

.footer-brand svg {
    color: var(--color-primary);
}

.footer-credit {
    font-size: 0.8125rem;
    color: var(--color-text-secondary);
}

.footer-copyright {
    font-size: 0.75rem;
    color: var(--color-text-tertiary);
}


.modal {
    display: none;
    position: fixed;
    inset: 0;
    z-index: 200;
    align-items: center;
    justify-content: center;
    padding: 24px;
}

.modal.active {
    display: flex;
}

.modal-overlay {
    position: absolute;
    inset: 0;
    background: rgba(15, 23, 42, 0.5);
    backdrop-filter: blur(4px);
}

.modal-content {
    position: relative;
    background: var(--color-surface);
    border-radius: var(--radius-xl);
    box-shadow: var(--shadow-xl);
    width: 100%;
    max-width: 480px;
    max-height: 90vh;
    overflow-y: auto;
    z-index: 1;
    animation: modalIn 250ms ease;
}

@keyframes modalIn {
    from {
        opacity: 0;
        transform: translateY(20px) scale(0.96);
    }
    to {
        opacity: 1;
        transform: translateY(0) scale(1);
    }
}

.modal-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 24px 24px 0;
}

.modal-header h2 {
    font-size: 1.25rem;
    font-weight: 600;
}

.modal-close {
    display: flex;
    align-items: center;
    justify-content: center;
    width: 32px;
    height: 32px;
    border-radius: var(--radius-md);
    color: var(--color-text-tertiary);
    transition: all var(--transition-fast);
}

.modal-close:hover {
    background: var(--color-bg);
    color: var(--color-text-primary);
}

.modal-body {
    padding: 24px;
}

.profile-info {
    display: flex;
    gap: 20px;
    margin-bottom: 24px;
}

.profile-avatar {
    width: 64px;
    height: 64px;
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: 50%;
    background: var(--color-primary-light);
    color: var(--color-primary);
    flex-shrink: 0;
}

.profile-details {
    display: flex;
    flex-direction: column;
    gap: 8px;
}

.profile-details p {
    font-size: 0.875rem;
    color: var(--color-text-secondary);
}

.profile-details strong {
    color: var(--color-text-primary);
    font-weight: 500;
}

.profile-actions {
    display: flex;
    justify-content: flex-end;
    padding-top: 16px;
    border-top: 1px solid var(--color-border);
}

.ai-tooltip {
    position: absolute;
    display: none;
    z-index: 1000;
    background: #fff;
    color: var(--color-text);
    padding: 6px;
    border-radius: var(--radius-md);
    border: 1px solid var(--color-border);
    box-shadow: var(--shadow-lg, 0 8px 28px rgba(0,0,0,.16));
    width: 300px;
    animation: ai-tooltip-in .14s ease;
}

@keyframes ai-tooltip-in {
    from { opacity: 0; transform: translateY(4px); }
    to   { opacity: 1; transform: translateY(0); }
}

.ai-tooltip-explain {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 6px;
    width: 100%;
    padding: 8px 12px;
    border: none;
    border-radius: 8px;
    background: var(--color-primary);
    color: #fff;
    font-size: 0.85rem;
    font-weight: 600;
    cursor: pointer;
    transition: background .15s ease;
}
.ai-tooltip-explain:hover { background: var(--color-primary-dark); }

.ai-tooltip-ask {
    display: flex;
    align-items: center;
    gap: 4px;
    margin-top: 6px;
}
.ai-tooltip-input {
    flex: 1;
    min-width: 0;
    padding: 8px 10px;
    border: 1px solid var(--color-border);
    border-radius: 8px;
    font-size: 0.85rem;
    font-family: var(--font-body);
    color: var(--color-text);
    outline: none;
    transition: border-color .15s ease;
}
.ai-tooltip-input:focus { border-color: var(--color-primary); }
.ai-tooltip-input::placeholder { color: var(--color-text-secondary); }
.ai-tooltip-send {
    flex: 0 0 auto;
    display: flex;
    align-items: center;
    justify-content: center;
    width: 34px;
    height: 34px;
    border: none;
    border-radius: 8px;
    background: var(--color-bg);
    color: var(--color-primary);
    cursor: pointer;
    transition: background .15s ease, color .15s ease;
}
.ai-tooltip-send:hover { background: var(--color-primary); color: #fff; }

.selected-text-box {
    background: var(--color-bg);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-md);
    padding: 16px;
    margin-bottom: 20px;
}

.selected-text-box strong {
    color: var(--color-primary);
    font-size: 0.875rem;
}

.selected-text-box p {
    margin: 8px 0 0 0;
    font-style: italic;
    color: var(--color-text-secondary);
}

.ai-loading {
    text-align: center;
    padding: 40px 20px;
}

.ai-spinner {
    width: 40px;
    height: 40px;
    border: 3px solid var(--color-border);
    border-top-color: var(--color-primary);
    border-radius: 50%;
    animation: spin 1s linear infinite;
    margin: 0 auto 16px;
}

@keyframes spin {
    to { transform: rotate(360deg); }
}

.explanation-result {
    animation: fadeIn 0.3s ease;
}

.explanation-header {
    display: flex;
    align-items: center;
    gap: 8px;
    margin-bottom: 16px;
    padding-bottom: 12px;
    border-bottom: 1px solid var(--color-border);
    color: var(--color-primary);
    font-weight: 600;
}

.explanation-body {
    line-height: 1.8;
    color: var(--color-text-primary);
}

.explanation-body h1,
.explanation-body h2,
.explanation-body h3 {
    margin: 20px 0 12px 0;
    color: var(--color-primary);
    font-weight: 600;
}

.explanation-body h1 {
    font-size: 1.25rem;
    border-bottom: 2px solid var(--color-primary-light);
    padding-bottom: 8px;
}

.explanation-body h2 {
    font-size: 1.1rem;
}

.explanation-body h3 {
    font-size: 1rem;
    color: var(--color-text-secondary);
}

.explanation-body p {
    margin: 12px 0;
    text-align: justify;
}

.explanation-body ul {
    margin: 12px 0;
    padding-left: 24px;
}

.explanation-body li {
    margin: 8px 0;
    line-height: 1.6;
}

.explanation-body strong {
    color: var(--color-accent);
    font-weight: 600;
}

.explanation-body em {
    color: var(--color-text-secondary);
    font-style: italic;
}

.explanation-body code {
    background: var(--color-bg);
    padding: 2px 6px;
    border-radius: 4px;
    font-family: 'Courier New', monospace;
    font-size: 0.9em;
    color: var(--color-primary);
}

@keyframes fadeIn {
    from { opacity: 0; transform: translateY(10px); }
    to { opacity: 1; transform: translateY(0); }
}

@media (max-width: 1024px) {
    .app-container {
        grid-template-columns: 1fr;
        grid-template-areas:
            "header"
            "main"
            "footer";
    }

    .sidebar {
        position: fixed;
        left: 0;
        top: 0;
        width: var(--sidebar-width);
        height: 100vh;
        transform: translateX(-100%);
        box-shadow: var(--shadow-xl);
    }

    .sidebar.open {
        transform: translateX(0);
    }

    .main-content {
        padding: 24px;
        max-width: 100%;
    }

    .app-footer {
        padding: 20px 24px;
    }

}

@media (max-width: 1024px) {
    .dashboard-grid {
        grid-template-columns: repeat(2, 1fr);
    }
    .study-stats-grid {
        grid-template-columns: repeat(3, 1fr);
    }
}

@media (max-width: 640px) {
    .onboarding-container {
        padding: 32px 16px;
    }

    .profile-setup-card {
        padding: 24px;
    }

    .onboarding-title {
        font-size: 1.5rem;
    }

    .radio-group,
    .checkbox-group {
        flex-direction: column;
    }

    .radio-option,
    .checkbox-option {
        width: 100%;
    }

    .main-content {
        padding: 20px 16px;
    }

    .page-header h1 {
        font-size: 1.375rem;
    }

    .dashboard-grid {
        grid-template-columns: 1fr;
    }

    .study-stats-grid {
        grid-template-columns: repeat(3, 1fr);
    }

    .ai-path-result {
        grid-template-columns: 1fr;
    }

    .wrong-answer-list {
        grid-template-columns: 1fr;
    }

    .chapter-header h1 {
        font-size: 1.5rem;
    }

    .chapter-nav-footer {
        flex-direction: column;
    }

    .chapter-nav-btn {
        width: 100%;
        justify-content: center;
    }

    .quick-chapters {
        grid-template-columns: 1fr;
    }

    .header-logo .logo-text {
        display: none;
    }

    .header-back-welcome span {
        display: none;
    }

    .header-back-welcome {
        padding: 6px 8px;
    }
}

.learning-tools {
    margin-top: 40px;
    border-top: 2px solid var(--color-border);
    padding-top: 24px;
}

.tool-tabs {
    display: flex;
    gap: 8px;
    margin-bottom: 24px;
    border-bottom: 2px solid var(--color-border);
    padding-bottom: 0;
}

.tool-tab {
    padding: 12px 24px;
    font-size: 0.9375rem;
    font-weight: 500;
    color: var(--color-text-secondary);
    background: none;
    border: none;
    border-bottom: 2px solid transparent;
    margin-bottom: -2px;
    cursor: pointer;
    transition: all var(--transition-fast);
}

.tool-tab:hover {
    color: var(--color-primary);
}

.tool-tab.active {
    color: var(--color-primary);
    border-bottom-color: var(--color-primary);
}

.tool-content {
    animation: fadeIn 0.3s ease;
}

.key-points-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
    gap: 16px;
}

.key-point-card {
    background: var(--color-surface);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-lg);
    padding: 20px;
    transition: box-shadow var(--transition-fast);
}

.key-point-card:hover {
    box-shadow: var(--shadow-md);
}

.key-point-icon {
    width: 40px;
    height: 40px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: var(--color-primary-light);
    color: var(--color-primary);
    border-radius: var(--radius-md);
    margin-bottom: 12px;
}

.key-point-card h4 {
    font-size: 1rem;
    font-weight: 600;
    margin-bottom: 8px;
    color: var(--color-text-primary);
}

.key-point-card p {
    font-size: 0.875rem;
    color: var(--color-text-secondary);
    line-height: 1.6;
}

.quiz-container {
    display: flex;
    flex-direction: column;
    gap: 24px;
}

.quiz-question {
    background: var(--color-surface);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-lg);
    padding: 24px;
}

.question-header {
    display: flex;
    align-items: center;
    gap: 12px;
    margin-bottom: 16px;
}

.question-number {
    background: var(--color-primary);
    color: white;
    padding: 4px 12px;
    border-radius: var(--radius-sm);
    font-size: 0.875rem;
    font-weight: 600;
}

.question-type {
    font-size: 0.8125rem;
    color: var(--color-text-tertiary);
}

.question-text {
    font-size: 1rem;
    font-weight: 500;
    margin-bottom: 16px;
    color: var(--color-text-primary);
}

.quiz-options {
    display: flex;
    flex-direction: column;
    gap: 10px;
}

.quiz-option {
    display: flex;
    align-items: center;
    gap: 12px;
    padding: 14px 16px;
    border: 1.5px solid var(--color-border);
    border-radius: var(--radius-md);
    cursor: pointer;
    transition: all var(--transition-fast);
    background: var(--color-surface);
}

.quiz-option:hover {
    border-color: var(--color-primary);
    background: var(--color-primary-light);
    transform: translateX(3px);
    box-shadow: var(--shadow-sm);
}

.quiz-option input {
    width: 18px;
    height: 18px;
    accent-color: var(--color-primary);
    flex-shrink: 0;
}

.quiz-option.correct {
    border-color: var(--color-success);
    background: var(--color-success-light);
}

.quiz-option.correct:hover {
    transform: none;
    box-shadow: none;
}

.quiz-option.incorrect {
    border-color: var(--color-accent);
    background: var(--color-accent-light);
}

.quiz-option.incorrect:hover {
    transform: none;
    box-shadow: none;
}

.quiz-feedback {
    margin-top: 16px;
    padding: 16px;
    border-radius: var(--radius-md);
}

.feedback-correct {
    display: none;
    align-items: center;
    gap: 8px;
    color: var(--color-success);
    font-weight: 500;
}

.feedback-incorrect {
    display: none;
    align-items: center;
    gap: 8px;
    color: var(--color-accent);
    font-weight: 500;
}

.quiz-feedback.show-correct .feedback-correct {
    display: flex;
}

.quiz-feedback.show-incorrect .feedback-incorrect {
    display: flex;
}

.quiz-summary {
    text-align: center;
    padding: 32px;
    background: var(--color-primary-light);
    border-radius: var(--radius-lg);
}

.summary-score {
    font-size: 2.5rem;
    font-weight: 700;
    color: var(--color-primary);
}

.score-total {
    font-size: 1.5rem;
    color: var(--color-text-secondary);
}

.summary-text {
    margin-top: 8px;
    color: var(--color-text-secondary);
}

.exercise-container {
    display: flex;
    flex-direction: column;
    gap: 24px;
}

.exercise-item {
    background: var(--color-surface);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-lg);
    padding: 24px;
}

.exercise-header {
    display: flex;
    align-items: center;
    gap: 12px;
    margin-bottom: 16px;
}

.exercise-number {
    background: var(--color-accent);
    color: white;
    padding: 4px 12px;
    border-radius: var(--radius-sm);
    font-size: 0.875rem;
    font-weight: 600;
}

.exercise-tag {
    font-size: 0.8125rem;
    color: var(--color-text-tertiary);
    background: var(--color-bg);
    padding: 2px 8px;
    border-radius: var(--radius-sm);
}

.exercise-text {
    font-size: 1rem;
    margin-bottom: 16px;
    color: var(--color-text-primary);
    line-height: 1.6;
}

.exercise-input {
    width: 100%;
    min-height: 120px;
    padding: 12px 16px;
    border: 1.5px solid var(--color-border);
    border-radius: var(--radius-md);
    font-family: inherit;
    font-size: 0.9375rem;
    resize: vertical;
    margin-bottom: 12px;
}

.exercise-input:focus {
    outline: none;
    border-color: var(--color-primary);
    box-shadow: 0 0 0 3px rgba(0, 78, 161, 0.1);
}

.exercise-hint-btn {
    margin-bottom: 12px;
}

.exercise-hint {
    padding: 16px;
    background: var(--color-primary-light);
    border-radius: var(--radius-md);
    border-left: 4px solid var(--color-primary);
    font-size: 0.875rem;
    line-height: 1.6;
}

.ai-sidebar {
    position: fixed;
    top: var(--header-height);
    right: 0;
    width: var(--ai-width);
    max-width: 92vw;
    height: calc(100vh - var(--header-height));
    background: var(--color-surface);
    border-left: 1px solid var(--color-border);
    display: flex;
    flex-direction: column;
    z-index: 90;
    transform: translateX(100%);
    transition: transform var(--transition-base);
    box-shadow: var(--shadow-lg);
}

.ai-sidebar.open {
    transform: translateX(0);
}

.ai-sidebar-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 12px 16px;
    border-bottom: 1px solid var(--color-border);
    background: var(--color-surface);
    flex-shrink: 0;
}

.ai-sidebar-tabs {
    display: flex;
    gap: 4px;
}

.ai-sidebar-tab {
    display: flex;
    align-items: center;
    gap: 6px;
    padding: 8px 16px;
    border: none;
    background: none;
    color: var(--color-text-secondary);
    font-size: 0.875rem;
    font-weight: 500;
    cursor: pointer;
    border-radius: var(--radius-md);
    transition: all var(--transition-fast);
}

.ai-sidebar-tab:hover {
    background: var(--color-bg);
    color: var(--color-text-primary);
}

.ai-sidebar-tab.active {
    background: var(--color-primary-light);
    color: var(--color-primary);
}

.ai-sidebar-close {
    display: flex;
    align-items: center;
    justify-content: center;
    width: 32px;
    height: 32px;
    border-radius: var(--radius-md);
    color: var(--color-text-tertiary);
    background: none;
    border: none;
    cursor: pointer;
    transition: all var(--transition-fast);
}

.ai-sidebar-close:hover {
    background: var(--color-bg);
    color: var(--color-text-primary);
}

/* ===== 会话头部 / 历史抽屉 ===== */
.ai-icon-btn {
    display: flex;
    align-items: center;
    justify-content: center;
    width: 32px;
    height: 32px;
    flex-shrink: 0;
    border-radius: var(--radius-md);
    color: var(--color-text-secondary);
    background: none;
    border: none;
    cursor: pointer;
    transition: all var(--transition-fast);
}
.ai-icon-btn:hover {
    background: var(--color-primary-light);
    color: var(--color-primary);
}
.ai-session-title {
    flex: 1;
    min-width: 0;
    margin: 0 8px;
    font-size: 0.9rem;
    font-weight: 600;
    color: var(--color-text-primary);
    text-align: center;
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
}

.ai-sessions-drawer {
    position: absolute;
    top: 57px;
    left: 0;
    right: 0;
    bottom: 0;
    z-index: 5;
    background: var(--color-surface);
    border-top: 1px solid var(--color-border);
    display: flex;
    flex-direction: column;
    animation: fadeIn 0.18s ease;
}
.ai-sessions-drawer-head {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 12px 16px;
    font-size: 0.85rem;
    font-weight: 600;
    color: var(--color-text-secondary);
    border-bottom: 1px solid var(--color-border);
}
.ai-sessions-list {
    flex: 1;
    overflow-y: auto;
    padding: 8px;
}
.ai-sessions-empty {
    text-align: center;
    color: var(--color-text-tertiary);
    font-size: 0.85rem;
    padding: 32px 16px;
}
.ai-session-item {
    display: flex;
    align-items: center;
    gap: 8px;
    padding: 10px 12px;
    border-radius: var(--radius-md);
    cursor: pointer;
    transition: background var(--transition-fast);
}
.ai-session-item:hover { background: var(--color-bg); }
.ai-session-item.active {
    background: var(--color-primary-light);
}
.ai-session-item-main { flex: 1; min-width: 0; }
.ai-session-item-title {
    font-size: 0.875rem;
    font-weight: 500;
    color: var(--color-text-primary);
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
}
.ai-session-item.active .ai-session-item-title { color: var(--color-primary); }
.ai-session-item-time {
    font-size: 0.72rem;
    color: var(--color-text-tertiary);
    margin-top: 2px;
}
.ai-session-del {
    flex-shrink: 0;
    width: 24px;
    height: 24px;
    border: none;
    background: none;
    color: var(--color-text-tertiary);
    border-radius: 6px;
    cursor: pointer;
    opacity: 0;
    transition: all var(--transition-fast);
}
.ai-session-item:hover .ai-session-del { opacity: 1; }
.ai-session-del:hover { background: var(--color-accent-light); color: var(--color-accent); }

/* ===== 消息内"存为笔记" ===== */
.ai-msg-actions {
    margin-top: 8px;
    display: flex;
    justify-content: flex-end;
}
.ai-msg-save {
    display: inline-flex;
    align-items: center;
    gap: 5px;
    padding: 4px 10px;
    font-size: 0.75rem;
    color: var(--color-primary);
    background: var(--color-primary-light);
    border: none;
    border-radius: 100px;
    cursor: pointer;
    transition: all var(--transition-fast);
}
.ai-msg-save:hover { filter: brightness(0.96); }
.ai-msg-save.saved {
    color: var(--color-success, #16a34a);
    background: rgba(22,163,74,0.1);
    pointer-events: none;
}

/* ④ 引用来源：行内角标 + 末尾参考小节 */
.ai-cite {
    display: inline-flex;
    align-items: center;
    margin: 0 2px;
    padding: 1px 7px;
    border: 1px solid rgba(0,78,161,0.28);
    border-radius: 999px;
    background: rgba(0,78,161,0.07);
    color: var(--color-primary);
    font-size: 0.72rem;
    font-weight: 600;
    line-height: 1.5;
    vertical-align: baseline;
    cursor: pointer;
    transition: background .15s ease, color .15s ease;
}
.ai-cite::before { content: "§"; margin-right: 2px; opacity: 0.6; }
.ai-cite:hover { background: var(--color-primary); color: #fff; }
/* 论文来源角标：外部链接，无 § 前缀 */
.ai-cite-paper { text-decoration: none; border-color: rgba(157,10,18,0.28); background: rgba(157,10,18,0.07); color: var(--color-accent, #9D0A12); }
.ai-cite-paper::before { content: none; }
.ai-cite-paper:hover { background: var(--color-accent, #9D0A12); color: #fff; }
/* 设备 SOP 角标：链接到设备官网详情页（绿色系），无 § 前缀 */
.ai-cite-instr { text-decoration: none; border-color: rgba(16,122,87,0.28); background: rgba(16,122,87,0.08); color: #0f7a57; }
.ai-cite-instr::before { content: none; }
a.ai-cite-instr { cursor: pointer; }
a.ai-cite-instr:hover { background: #0f7a57; color: #fff; }
span.ai-cite-instr { cursor: default; }

.ai-sources {
    margin-top: 12px;
    padding-top: 10px;
    border-top: 1px dashed var(--color-border);
}
.ai-sources-label {
    font-size: 0.72rem;
    color: var(--color-text-secondary);
    letter-spacing: 0.02em;
    margin-bottom: 6px;
}
.ai-sources-list {
    display: flex;
    flex-direction: column;
    gap: 4px;
}
.ai-source-item {
    display: flex;
    align-items: baseline;
    gap: 6px;
    width: 100%;
    text-align: left;
    padding: 5px 8px;
    border: 1px solid var(--color-border);
    border-radius: 7px;
    background: var(--color-bg);
    color: var(--color-text);
    font-size: 0.78rem;
    line-height: 1.4;
    cursor: pointer;
    transition: border-color .15s ease, background .15s ease;
}
.ai-source-item:hover { border-color: var(--color-primary); background: rgba(0,78,161,0.05); }
.ai-source-ch {
    flex: 0 0 auto;
    color: var(--color-primary);
    font-weight: 600;
    font-size: 0.72rem;
}

/* 外部参考（联网搜索）*/
.ai-sources-web { border-top-color: rgba(157,10,18,0.3); }
.ai-source-web {
    align-items: flex-start;
    text-decoration: none;
}
.ai-source-web-icon {
    flex: 0 0 auto;
    color: var(--color-accent);
    font-weight: 700;
}
.ai-source-web-body { display: flex; flex-direction: column; gap: 1px; min-width: 0; }
.ai-source-web-title {
    color: var(--color-text);
    overflow: hidden;
    text-overflow: ellipsis;
    display: -webkit-box;
    -webkit-line-clamp: 2;
    -webkit-box-orient: vertical;
}
.ai-source-web:hover .ai-source-web-title { color: var(--color-accent); }
.ai-source-web-host { font-size: 0.7rem; color: var(--color-text-secondary); }

/* 相似度小标：靠右显示，单色低调 */
.ai-source-sim {
    flex: 0 0 auto;
    margin-left: auto;
    align-self: center;
    font-size: 0.66rem;
    font-weight: 600;
    color: var(--color-text-secondary);
    background: rgba(0,0,0,0.05);
    border-radius: 999px;
    padding: 1px 6px;
    font-variant-numeric: tabular-nums;
}
.ai-source-web .ai-source-sim { align-self: flex-start; }

.ai-sidebar-content {
    flex: 1;
    overflow-y: auto;
    overflow-x: hidden;
    display: flex;
    flex-direction: column;
}

.ai-panel {
    display: none;
    flex-direction: column;
    height: 100%;
}

.ai-panel.active {
    display: flex;
}

.ai-panel-empty {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    gap: 12px;
    padding: 40px 24px;
    text-align: center;
    color: var(--color-text-tertiary);
    flex: 1;
}

.ai-panel-empty p {
    font-size: 0.9375rem;
    font-weight: 500;
    color: var(--color-text-secondary);
    margin: 0;
}

.ai-panel-empty-hint {
    font-size: 0.8125rem;
    color: var(--color-text-tertiary);
}

.ai-explanation-result {
    display: flex;
    flex-direction: column;
    height: 100%;
    overflow-y: auto;
    padding: 16px;
}

.ai-explanation-result.hidden {
    display: none;
}

.selected-text-box {
    background: var(--color-bg);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-md);
    padding: 12px;
    margin-bottom: 16px;
    flex-shrink: 0;
}

.selected-text-box strong {
    color: var(--color-primary);
    font-size: 0.8125rem;
    display: block;
    margin-bottom: 6px;
}

.selected-text-content {
    margin: 0;
    font-style: italic;
    color: var(--color-text-secondary);
    font-size: 0.875rem;
    line-height: 1.5;
}

.ai-explanation-body {
    flex: 1;
    overflow-y: auto;
}

.ai-explanation-body .explanation-result {
    animation: fadeIn 0.3s ease;
}

.ai-explanation-body .explanation-header {
    display: flex;
    align-items: center;
    gap: 8px;
    margin-bottom: 12px;
    padding-bottom: 8px;
    border-bottom: 1px solid var(--color-border);
    color: var(--color-primary);
    font-weight: 600;
    font-size: 0.875rem;
}

.ai-explanation-body .explanation-body {
    line-height: 1.7;
    color: var(--color-text-primary);
    font-size: 0.9375rem;
}

.ai-explanation-body .explanation-body h1,
.ai-explanation-body .explanation-body h2,
.ai-explanation-body .explanation-body h3 {
    margin: 16px 0 10px 0;
    color: var(--color-primary);
    font-weight: 600;
}

.ai-explanation-body .explanation-body h1 {
    font-size: 1.1rem;
}

.ai-explanation-body .explanation-body h2 {
    font-size: 1rem;
}

.ai-explanation-body .explanation-body h3 {
    font-size: 0.9375rem;
    color: var(--color-text-secondary);
}

.ai-explanation-body .explanation-body p {
    margin: 10px 0;
}

.ai-explanation-body .explanation-body ul {
    margin: 10px 0;
    padding-left: 20px;
}

.ai-explanation-body .explanation-body li {
    margin: 6px 0;
}

.ai-explanation-body .explanation-body strong {
    color: var(--color-accent);
}

.explanation-actions {
    margin-top: 12px;
    padding-top: 10px;
    border-top: 1px solid var(--color-border);
    display: flex;
    justify-content: flex-end;
}

.explanation-question-area {
    display: flex;
    gap: 8px;
    align-items: center;
    padding: 8px 0;
    animation: form-fade-in 0.3s ease;
}

.explanation-question-input {
    flex: 1;
    padding: 8px 12px;
    border: 1px solid var(--color-primary);
    border-radius: 8px;
    font-size: 0.875rem;
    background: var(--color-surface);
    color: var(--color-text);
    outline: none;
    transition: box-shadow 0.2s ease;
}

.explanation-question-input:focus {
    box-shadow: 0 0 0 3px rgba(0, 78, 161, 0.15);
}

.explanation-question-input::placeholder {
    color: var(--color-text-tertiary);
    font-size: 0.8125rem;
}

.explanation-question-send {
    flex-shrink: 0;
    display: inline-flex;
    align-items: center;
    gap: 4px;
    padding: 8px 16px;
    border-radius: 8px;
    font-size: 0.875rem;
    white-space: nowrap;
}

.explanation-question-display {
    margin-top: 8px;
    padding: 8px 12px;
    background: #f0f6fc;
    border-left: 3px solid var(--color-primary);
    border-radius: 0 6px 6px 0;
    font-size: 0.8125rem;
    color: var(--color-text-secondary);
}

.explanation-conversation {
    display: flex;
    flex-direction: column;
    gap: 16px;
}

.explanation-qa-item {
    position: relative;
    border: 1px solid var(--color-border);
    border-radius: var(--radius-md);
    overflow: hidden;
    animation: fadeIn 0.3s ease;
    transition: border-color 0.2s ease, box-shadow 0.2s ease;
}

/* Highlight an item when its checkbox is selected */
.explanation-qa-item:has(.qa-select:checked) {
    border-color: var(--color-primary);
    box-shadow: 0 0 0 1px var(--color-primary);
}

.explanation-qa-check {
    position: absolute;
    top: 9px;
    right: 10px;
    z-index: 1;
    display: inline-flex;
    cursor: pointer;
}
.explanation-qa-check input {
    width: 16px;
    height: 16px;
    cursor: pointer;
    accent-color: var(--color-primary);
}

.explanation-qa-question {
    display: flex;
    align-items: flex-start;
    gap: 8px;
    padding: 10px 36px 10px 14px;
    background: #fef7f0;
    font-size: 0.875rem;
    font-weight: 500;
    color: var(--color-text-secondary);
    border-bottom: 1px solid var(--color-border);
}

.explanation-qa-question svg {
    flex-shrink: 0;
    margin-top: 2px;
}

.explanation-qa-answer {
    padding: 14px;
    font-size: 0.875rem;
    line-height: 1.7;
    color: var(--color-text-primary);
}

.explanation-qa-answer h1,
.explanation-qa-answer h2,
.explanation-qa-answer h3 {
    margin-top: 16px;
    margin-bottom: 8px;
}

.explanation-qa-answer h1 { font-size: 1.25rem; }
.explanation-qa-answer h2 { font-size: 1.1rem; }
.explanation-qa-answer h3 { font-size: 1rem; }

.explanation-qa-answer p {
    margin-bottom: 8px;
}

.explanation-qa-answer ul,
.explanation-qa-answer ol {
    padding-left: 20px;
    margin-bottom: 8px;
}

.explanation-qa-answer li {
    margin-bottom: 4px;
}

.explanation-qa-answer strong {
    color: var(--color-accent);
}

.explanation-qa-answer code {
    background: var(--color-bg);
    padding: 1px 5px;
    border-radius: 3px;
    font-size: 0.8125rem;
    color: var(--color-accent);
}

.explanation-save-all {
    display: flex;
    align-items: center;
    gap: 12px;
    margin-top: 0;
    padding-top: 8px;
    border-top: 1px dashed var(--color-border);
    justify-content: flex-end;
}

.qa-select-all-label {
    display: inline-flex;
    align-items: center;
    gap: 5px;
    font-size: 0.8125rem;
    color: var(--color-text-secondary);
    cursor: pointer;
    margin-right: auto;
}
.qa-select-all-label input {
    width: 15px;
    height: 15px;
    cursor: pointer;
    accent-color: var(--color-primary);
}

.explanation-followup {
    display: flex;
    gap: 8px;
    align-items: center;
    padding: 12px 0 4px;
    border-top: 1px solid var(--color-border);
    margin-top: 4px;
}

.btn-outline {
    display: inline-flex;
    align-items: center;
    gap: 5px;
    padding: 6px 14px;
    border: 1px solid var(--color-border);
    border-radius: 6px;
    background: var(--color-surface);
    color: var(--color-text-secondary);
    font-size: 0.8125rem;
    cursor: pointer;
    transition: all 0.2s ease;
}

.btn-outline:hover {
    border-color: var(--color-primary);
    color: var(--color-primary);
    background: #e8f1fb;
}

.btn-outline.saved {
    border-color: var(--color-success);
    color: var(--color-success);
    background: #ecfdf5;
    pointer-events: none;
}

.ai-sidebar-footer {
    padding: 8px 16px;
    border-top: 1px solid var(--color-border);
    background: var(--color-surface);
    flex-shrink: 0;
}

.ai-sidebar-toggle {
    position: fixed;
    bottom: 24px;
    right: 24px;
    width: 56px;
    height: 56px;
    border-radius: 50%;
    background: var(--color-primary);
    color: white;
    border: none;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    box-shadow: var(--shadow-lg);
    transition: transform 0.2s ease, box-shadow 0.2s ease, opacity 0.2s ease;
    z-index: 1000;
}

.ai-sidebar-toggle:hover {
    transform: scale(1.05);
    box-shadow: var(--shadow-xl);
    background: var(--color-primary-dark);
}

.ai-sidebar-toggle.hidden {
    opacity: 0;
    pointer-events: none;
}

.ai-sidebar-toggle svg {
    width: 28px;
    height: 28px;
}

#ai-chat-panel {
    padding: 0;
}

#ai-chat-panel .ai-chat-messages {
    flex: 1;
    overflow-y: auto;
    padding: 16px;
    display: flex;
    flex-direction: column;
    gap: 12px;
    background: var(--color-bg);
}

#ai-chat-panel .ai-message {
    display: flex;
    gap: 10px;
    max-width: 90%;
    animation: fadeIn 0.3s ease;
}

#ai-chat-panel .ai-message-user {
    align-self: flex-end;
    flex-direction: row-reverse;
}

#ai-chat-panel .ai-message-assistant {
    align-self: flex-start;
}

#ai-chat-panel .ai-message-avatar {
    width: 28px;
    height: 28px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    flex-shrink: 0;
    background: var(--color-primary-light);
    color: var(--color-primary);
}

#ai-chat-panel .ai-message-user .ai-message-avatar {
    background: var(--color-primary);
    color: white;
}

#ai-chat-panel .ai-message-content {
    padding: 10px 14px;
    border-radius: var(--radius-lg);
    font-size: 0.875rem;
    line-height: 1.6;
    word-wrap: break-word;
}

#ai-chat-panel .ai-message-assistant .ai-message-content {
    background: var(--color-surface);
    border: 1px solid var(--color-border);
    border-top-left-radius: 4px;
}

#ai-chat-panel .ai-message-user .ai-message-content {
    background: var(--color-primary);
    color: white;
    border-top-right-radius: 4px;
}

#ai-chat-panel .ai-message-content p {
    margin: 0 0 8px;
}
#ai-chat-panel .ai-message-content > *:last-child { margin-bottom: 0; }

/* Markdown 渲染样式（仅 AI 回答） */
#ai-chat-panel .ai-message-assistant .ai-message-content h1,
#ai-chat-panel .ai-message-assistant .ai-message-content h2,
#ai-chat-panel .ai-message-assistant .ai-message-content h3,
#ai-chat-panel .ai-message-assistant .ai-message-content h4 {
    margin: 12px 0 6px;
    font-weight: 700;
    line-height: 1.35;
}
#ai-chat-panel .ai-message-assistant .ai-message-content h1 { font-size: 1.1rem; }
#ai-chat-panel .ai-message-assistant .ai-message-content h2 { font-size: 1.02rem; }
#ai-chat-panel .ai-message-assistant .ai-message-content h3 { font-size: 0.95rem; }
#ai-chat-panel .ai-message-assistant .ai-message-content h4 { font-size: 0.9rem; }
#ai-chat-panel .ai-message-assistant .ai-message-content ul,
#ai-chat-panel .ai-message-assistant .ai-message-content ol {
    margin: 6px 0 8px;
    padding-left: 22px;
}
#ai-chat-panel .ai-message-assistant .ai-message-content li { margin: 3px 0; }
#ai-chat-panel .ai-message-assistant .ai-message-content li::marker { color: var(--color-primary); }
#ai-chat-panel .ai-message-assistant .ai-message-content code {
    background: var(--color-bg);
    border: 1px solid var(--color-border);
    border-radius: 4px;
    padding: 1px 5px;
    font-family: 'SF Mono', 'Menlo', 'Consolas', monospace;
    font-size: 0.82em;
}
#ai-chat-panel .ai-message-assistant .ai-message-content pre {
    background: #1e293b;
    color: #e2e8f0;
    border-radius: var(--radius-md);
    padding: 12px 14px;
    overflow-x: auto;
    margin: 8px 0;
    font-size: 0.82rem;
    line-height: 1.55;
}
#ai-chat-panel .ai-message-assistant .ai-message-content pre code {
    background: none;
    border: none;
    padding: 0;
    color: inherit;
}
#ai-chat-panel .ai-message-assistant .ai-message-content blockquote {
    margin: 8px 0;
    padding: 4px 12px;
    border-left: 3px solid var(--color-primary);
    background: var(--color-primary-light);
    color: var(--color-text-secondary);
    border-radius: 0 6px 6px 0;
}
#ai-chat-panel .ai-message-assistant .ai-message-content table {
    width: 100%;
    border-collapse: collapse;
    margin: 8px 0;
    font-size: 0.82rem;
}
#ai-chat-panel .ai-message-assistant .ai-message-content th,
#ai-chat-panel .ai-message-assistant .ai-message-content td {
    border: 1px solid var(--color-border);
    padding: 6px 10px;
    text-align: left;
}
#ai-chat-panel .ai-message-assistant .ai-message-content th {
    background: var(--color-bg);
    font-weight: 600;
}
#ai-chat-panel .ai-message-assistant .ai-message-content a {
    color: var(--color-primary);
    text-decoration: underline;
}
#ai-chat-panel .ai-message-assistant .ai-message-content img { max-width: 100%; border-radius: 6px; }

/* ===== AI 首页（落地页）===== */
.chat-home {
    display: flex;
    flex-direction: column;
    gap: 20px;
    padding: 8px 4px;
}
.chat-home-hero {
    display: flex;
    flex-direction: column;
    align-items: center;
    text-align: center;
    gap: 10px;
    padding: 24px 16px 20px;
}
.chat-home-icon {
    width: 56px;
    height: 56px;
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: 50%;
    color: var(--color-primary);
    background: var(--color-primary-light);
}
.chat-home-hero h3 {
    margin: 4px 0 0;
    font-size: 1.1rem;
    font-weight: 700;
    color: var(--color-text-primary);
}
.chat-home-hero p {
    margin: 0;
    font-size: 0.85rem;
    color: var(--color-text-secondary);
    line-height: 1.6;
    max-width: 320px;
}
.chat-home-new {
    margin-top: 8px;
}
.chat-home-recent {
    display: flex;
    flex-direction: column;
    gap: 6px;
}
.chat-home-recent-title {
    font-size: 0.78rem;
    font-weight: 600;
    color: var(--color-text-tertiary);
    padding: 0 4px 2px;
}
.chat-home-session {
    display: flex;
    flex-direction: column;
    align-items: flex-start;
    gap: 3px;
    width: 100%;
    padding: 10px 14px;
    text-align: left;
    background: var(--color-surface);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-md);
    cursor: pointer;
    transition: all var(--transition-fast);
}
.chat-home-session:hover {
    border-color: var(--color-primary);
    background: var(--color-primary-light);
}
.chat-home-session-title {
    font-size: 0.875rem;
    font-weight: 500;
    color: var(--color-text-primary);
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
    max-width: 100%;
}
.chat-home-session-time {
    font-size: 0.72rem;
    color: var(--color-text-tertiary);
}

#ai-chat-panel .ai-chat-input-area {
    display: flex;
    gap: 8px;
    padding: 12px 16px;
    background: var(--color-surface);
    border-top: 1px solid var(--color-border);
}

#ai-chat-panel .ai-chat-input-area textarea {
    flex: 1;
    padding: 8px 12px;
    border: 1.5px solid var(--color-border);
    border-radius: var(--radius-lg);
    font-family: inherit;
    font-size: 0.875rem;
    resize: none;
    max-height: 80px;
    outline: none;
}

#ai-chat-panel .ai-chat-input-area textarea:focus {
    border-color: var(--color-primary);
    box-shadow: 0 0 0 3px rgba(0, 78, 161, 0.1);
}

#ai-chat-panel .ai-chat-send {
    width: 36px;
    height: 36px;
    border-radius: 50%;
    background: var(--color-primary);
    color: white;
    border: none;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    flex-shrink: 0;
    transition: background 0.2s ease;
}

#ai-chat-panel .ai-chat-send:hover {
    background: var(--color-primary-dark);
}

#ai-chat-panel .ai-chat-send:disabled {
    background: var(--color-border);
    cursor: not-allowed;
}

.ai-typing-indicator {
    display: flex;
    gap: 4px;
    padding: 10px 14px;
    background: var(--color-surface);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-lg);
    border-top-left-radius: 4px;
    width: fit-content;
}

.ai-typing-indicator span {
    width: 8px;
    height: 8px;
    background: var(--color-text-tertiary);
    border-radius: 50%;
    animation: typingBounce 1.4s infinite ease-in-out both;
}

.ai-typing-indicator span:nth-child(1) {
    animation-delay: -0.32s;
}

.ai-typing-indicator span:nth-child(2) {
    animation-delay: -0.16s;
}

@keyframes typingBounce {
    0%, 80%, 100% {
        transform: scale(0);
    }
    40% {
        transform: scale(1);
    }
}

.ai-sidebar-footer .ai-settings-toggle {
    display: flex;
    align-items: center;
    gap: 6px;
    background: none;
    border: none;
    color: var(--color-text-tertiary);
    font-size: 0.75rem;
    cursor: pointer;
    padding: 4px 0;
    width: 100%;
    justify-content: center;
}

.ai-sidebar-footer .ai-settings-toggle:hover {
    color: var(--color-primary);
}

.ai-sidebar-footer .ai-settings-panel {
    padding: 12px 0 0;
}

.ai-sidebar-footer .ai-settings-content {
    display: flex;
    flex-direction: column;
    gap: 8px;
}

.ai-sidebar-footer .ai-settings-content label {
    font-size: 0.875rem;
    font-weight: 500;
    color: var(--color-text-secondary);
}

.ai-sidebar-footer .ai-settings-content input {
    padding: 8px 12px;
    border: 1px solid var(--color-border);
    border-radius: var(--radius-sm);
    font-size: 0.875rem;
    background: var(--color-bg);
}

.ai-settings-hint {
    font-size: 0.75rem;
    color: var(--color-text-tertiary);
    margin: 0;
}

.ai-sidebar-footer .ai-settings-content .btn-sm {
    padding: 6px 12px;
    font-size: 0.875rem;
}

@media (max-width: 1024px) {
    .ai-sidebar {
        width: 340px;
    }
}

@media (max-width: 768px) {
    .ai-sidebar {
        width: 100%;
        top: 0;
        height: 100vh;
        z-index: 200;
    }

    .ai-sidebar-toggle {
        bottom: 16px;
        right: 16px;
        width: 48px;
        height: 48px;
    }

    .ai-sidebar-toggle svg {
        width: 24px;
        height: 24px;
    }
}

@media (prefers-reduced-motion: reduce) {
    *,
    *::before,
    *::after {
        animation-duration: 0.01ms !important;
        animation-iteration-count: 1 !important;
        transition-duration: 0.01ms !important;
    }
}

.mermaid {
    text-align: center;
    margin: 24px 0;
}

.mermaid svg {
    max-width: 100%;
    height: auto;
}

/* ===== Font consistency ===== */
.chapter-content {
    font-family: var(--font-body);
}

.chapter-content h1, .chapter-content h2, .chapter-content h3,
.chapter-content h4, .chapter-content h5, .chapter-content h6 {
    font-family: var(--font-display);
}

/* 目录/子标题跳转时，让标题行避开吸顶导航，不被遮住 */
.chapter-header,
.chapter-content h1, .chapter-content h2, .chapter-content h3,
.chapter-content h4, .chapter-content h5, .chapter-content h6 {
    scroll-margin-top: calc(var(--header-height) + 24px);
}

.chapter-content table {
    font-family: var(--font-body);
}

.chapter-content code, .chapter-content pre {
    font-family: 'SF Mono', 'Fira Code', 'Consolas', monospace;
}

/* ===== Image Lightbox ===== */
.image-lightbox {
    display: none;
    position: fixed;
    inset: 0;
    z-index: 300;
    background: rgba(0, 0, 0, 0.85);
    align-items: center;
    justify-content: center;
    cursor: zoom-out;
    padding: 40px;
}

.image-lightbox.active {
    display: flex;
}

.image-lightbox img {
    max-width: 90vw;
    max-height: 85vh;
    object-fit: contain;
    border-radius: var(--radius-md);
    box-shadow: var(--shadow-xl);
    cursor: default;
}

.image-lightbox-close {
    position: absolute;
    top: 20px;
    right: 20px;
    width: 44px;
    height: 44px;
    border-radius: 50%;
    background: rgba(255, 255, 255, 0.15);
    color: white;
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    border: none;
    transition: background 0.2s;
    font-size: 1.2rem;
}

.image-lightbox-close:hover {
    background: rgba(255, 255, 255, 0.3);
}

.chapter-content img:not(.mermaid svg *) {
    cursor: zoom-in;
    transition: opacity 0.2s;
}

.chapter-content img:not(.mermaid svg *):hover {
    opacity: 0.85;
}

.chapter-content .figure img {
    cursor: zoom-in;
}

/* ===== Learning Objectives ===== */
.learning-objectives {
    background: linear-gradient(135deg, var(--color-primary-light) 0%, #e8f4f8 100%);
    border: 1px solid var(--color-primary);
    border-left: 4px solid var(--color-primary);
    border-radius: var(--radius-md);
    padding: 20px 24px;
    margin-bottom: 28px;
}

.learning-objectives-header {
    display: flex;
    align-items: center;
    gap: 10px;
    margin-bottom: 12px;
}

.learning-objectives-header h4 {
    font-size: 1rem;
    font-weight: 600;
    color: var(--color-primary);
    margin: 0;
}

.learning-objectives-header svg {
    color: var(--color-primary);
    flex-shrink: 0;
}

.learning-objectives-list {
    display: flex;
    flex-direction: column;
    gap: 8px;
}

.learning-objective-item {
    display: flex;
    align-items: flex-start;
    gap: 10px;
    font-size: 0.9rem;
    color: var(--color-text-secondary);
    line-height: 1.5;
}

.learning-objective-item .obj-badge {
    flex-shrink: 0;
    padding: 2px 10px;
    border-radius: 12px;
    font-size: 0.7rem;
    font-weight: 600;
    margin-top: 1px;
}

.obj-badge.basic {
    background: #dbeafe;
    color: #1e40af;
}

.obj-badge.advanced {
    background: #fce7f3;
    color: #9d174d;
}

/* ===== Study Stats (inside progress card) ===== */
.study-stats-grid {
    display: grid;
    grid-template-columns: repeat(5, 1fr);
    gap: 10px;
    margin-bottom: 14px;
}

.study-stat-item {
    text-align: center;
    padding: 14px 8px 12px;
    background: var(--color-bg);
    border-radius: var(--radius-md);
    border: 1px solid var(--color-border-light);
    transition: all var(--transition-base);
    position: relative;
}

.study-stat-item:hover {
    background: var(--color-primary-light);
    border-color: rgba(0, 78, 161, 0.12);
    transform: translateY(-2px);
    box-shadow: var(--shadow-sm);
}

.study-stat-value {
    font-size: 1.25rem;
    font-weight: 700;
    color: var(--color-primary);
    line-height: 1.2;
    letter-spacing: -0.01em;
}

.study-stat-label {
    font-size: 0.7rem;
    color: var(--color-text-tertiary);
    margin-top: 4px;
    font-weight: 500;
}

.study-stat-item:nth-child(1) .study-stat-value { color: var(--color-primary); }
.study-stat-item:nth-child(2) .study-stat-value { color: #0d9488; }
.study-stat-item:nth-child(3) .study-stat-value { color: #7c3aed; }
.study-stat-item:nth-child(4) .study-stat-value { color: var(--color-accent); }
.study-stat-item:nth-child(5) .study-stat-value { color: #f59e0b; }

.study-stat-bar {
    height: 6px;
    background: var(--color-border-light);
    border-radius: 3px;
    overflow: hidden;
    margin-bottom: 6px;
}

.study-stat-bar-fill {
    height: 100%;
    background: linear-gradient(90deg, var(--color-primary), #0d9488);
    border-radius: 3px;
    transition: width 0.5s ease;
    position: relative;
}

.study-stat-bar-fill::after {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: linear-gradient(180deg, rgba(255,255,255,0.3) 0%, transparent 50%);
    border-radius: 3px;
}

.study-stat-bar-label {
    display: flex;
    justify-content: space-between;
    font-size: 0.75rem;
    color: var(--color-text-tertiary);
}

.study-stat-bar-label span:last-child {
    color: #0d9488;
    font-weight: 600;
}

/* ===== Mind Map ===== */
.mindmap-card {
    grid-column: 1 / -1;
}

.mindmap-card .card-icon {
    color: #7c3aed;
    background: #f5f3ff;
}

.mindmap-container {
    width: 100%;
    overflow-x: auto;
    padding: 16px 0 8px;
}

.mindmap-svg {
    width: 100%;
    max-width: 960px;
    min-width: 520px;
    margin: 0 auto;
    display: block;
}

/* ===== Sidebar Sub-headings ===== */
.nav-sub-toggle {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    width: 18px;
    height: 18px;
    flex-shrink: 0;
    margin-left: 2px;
    border-radius: 4px;
    color: var(--color-text-tertiary);
    transition: transform var(--transition-fast), background var(--transition-fast);
}
.nav-sub-toggle:hover {
    background: rgba(0, 78, 161, 0.1);
    color: var(--color-primary);
}
.nav-chapter-row.expanded-sub .nav-sub-toggle {
    transform: rotate(180deg);
}

.nav-subheadings {
    display: none;
    flex-direction: column;
    padding: 4px 0 8px 48px;
    font-size: 0.75rem;
}

.nav-chapter-row.expanded-sub .nav-subheadings {
    display: flex;
}

.nav-subheading {
    padding: 4px 8px;
    color: var(--color-text-tertiary);
    text-decoration: none;
    border-radius: var(--radius-sm);
    transition: all var(--transition-fast);
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
}

.nav-subheading:hover {
    color: var(--color-primary);
    background: var(--color-primary-light);
}

/* ===== Wrong Answer Book ===== */
.wrong-answer-book {
    grid-column: 1 / -1;
}

.wrong-answer-book .card-icon {
    color: var(--color-accent);
    background: var(--color-accent-light);
}

.wrong-answer-list {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 10px;
}

.wrong-answer-item {
    display: flex;
    flex-direction: column;
    gap: 8px;
    padding: 16px 18px;
    background: var(--color-bg);
    border-radius: var(--radius-md);
    font-size: 0.8125rem;
    border-left: 3px solid var(--color-accent);
    border: 1px solid var(--color-border-light);
    border-left: 3px solid var(--color-accent);
    transition: all var(--transition-base);
}

.wrong-answer-item:hover {
    background: var(--color-accent-light);
    transform: translateX(3px);
    box-shadow: var(--shadow-sm);
}

.wrong-answer-item .wa-header {
    display: flex;
    align-items: center;
    gap: 8px;
}

.wrong-answer-item .wa-chapter {
    flex-shrink: 0;
    font-weight: 600;
    color: var(--color-primary);
    font-size: 0.75rem;
    background: var(--color-primary-light);
    padding: 2px 8px;
    border-radius: 4px;
}

.wrong-answer-item .wa-date {
    font-size: 0.7rem;
    color: var(--color-text-tertiary);
}

.wrong-answer-item .wa-question {
    font-size: 0.875rem;
    color: var(--color-text-primary);
    font-weight: 500;
    line-height: 1.5;
}

.wrong-answer-item .wa-detail {
    font-size: 0.75rem;
    color: var(--color-text-secondary);
    line-height: 1.5;
}

/* ===== Highlight & Note Toolbar ===== */
.highlight-note-btn {
    position: absolute;
    display: none;
    background: var(--color-surface);
    color: var(--color-text-primary);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-md);
    padding: 4px;
    font-size: 0.8rem;
    cursor: pointer;
    z-index: 1000;
    box-shadow: var(--shadow-lg);
    white-space: nowrap;
}

.highlight-note-btn .sub-options {
    display: flex;
    gap: 2px;
}

.highlight-note-btn .sub-option {
    padding: 6px 12px;
    border-radius: calc(var(--radius-md) - 2px);
    cursor: pointer;
    transition: all var(--transition-fast);
    font-size: 0.8125rem;
    font-weight: 500;
}

.highlight-note-btn .sub-option:hover {
    background: var(--color-primary-light);
    color: var(--color-primary);
}

/* ===== Chapter content highlights ===== */
.chapter-content mark.user-highlight {
    background: #fef08a;
    border-radius: 2px;
    padding: 0 2px;
    cursor: pointer;
    transition: all var(--transition-fast);
    position: relative;
}

.chapter-content mark.user-highlight:hover {
    background: #fde047;
}

.chapter-content mark.user-highlight.has-note {
    background: #fde68a;
    border-bottom: 2px dashed #f59e0b;
    cursor: pointer;
}

.chapter-content mark.user-highlight.has-note::after {
    content: '📎';
    position: absolute;
    top: -10px;
    right: -6px;
    font-size: 10px;
    pointer-events: none;
}

.chapter-content .user-highlight-mark {
    background: #fef08a;
    border-radius: 2px;
    padding: 0 2px;
    cursor: pointer;
    transition: all var(--transition-fast);
}

.chapter-content .user-highlight-mark:hover {
    background: #fde047;
}

.chapter-content .user-highlight-mark.has-note {
    background: #fde68a;
    border-bottom: 2px dashed #f59e0b;
    cursor: pointer;
}

/* ===== Note Annotation (Word-comment style) ===== */
.note-annotation {
    position: relative;
    background: #fffdf5;
    border: 1px solid #f59e0b;
    border-left: 4px solid #f59e0b;
    border-radius: var(--radius-md);
    padding: 14px 16px;
    margin: 8px 0 8px 24px;
    font-size: 0.875rem;
    line-height: 1.6;
    box-shadow: var(--shadow-xs);
    animation: annotationIn 0.25s ease;
}

@keyframes annotationIn {
    from { opacity: 0; transform: translateX(-8px); }
    to { opacity: 1; transform: translateX(0); }
}

.note-annotation .note-annotation-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    margin-bottom: 8px;
}

.note-annotation .note-annotation-label {
    font-size: 0.7rem;
    font-weight: 700;
    color: #b45309;
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

.note-annotation .note-annotation-delete {
    font-size: 0.75rem;
    color: var(--color-text-tertiary);
    cursor: pointer;
    padding: 2px 6px;
    border-radius: 3px;
    transition: all var(--transition-fast);
}

.note-annotation .note-annotation-delete:hover {
    color: var(--color-accent);
    background: var(--color-accent-light);
}

.note-annotation .note-annotation-context {
    font-size: 0.75rem;
    color: var(--color-text-tertiary);
    font-style: italic;
    margin-bottom: 6px;
    padding-bottom: 6px;
    border-bottom: 1px dashed var(--color-border);
}

.note-annotation .note-annotation-content {
    color: var(--color-text-primary);
}

/* ===== Inline Note Input ===== */
.note-input-popup {
    position: absolute;
    display: none;
    background: var(--color-surface);
    border: 1.5px solid #f59e0b;
    border-radius: var(--radius-md);
    padding: 12px;
    z-index: 1001;
    box-shadow: var(--shadow-lg);
    width: 280px;
}

.note-input-popup textarea {
    width: 100%;
    min-height: 80px;
    padding: 10px 12px;
    border: 1.5px solid var(--color-border);
    border-radius: var(--radius-sm);
    font-family: inherit;
    font-size: 0.875rem;
    resize: vertical;
    margin-bottom: 8px;
    line-height: 1.6;
}

.note-input-popup textarea:focus {
    outline: none;
    border-color: #f59e0b;
    box-shadow: 0 0 0 3px rgba(245, 158, 11, 0.1);
}

.note-input-popup .note-input-actions {
    display: flex;
    gap: 6px;
    justify-content: flex-end;
}

.note-input-popup .note-input-context {
    font-size: 0.7rem;
    color: var(--color-text-tertiary);
    margin-bottom: 8px;
    font-style: italic;
    line-height: 1.4;
    max-height: 48px;
    overflow: hidden;
    text-overflow: ellipsis;
}

/* ===== Notes Modal ===== */
.notes-modal .modal-content {
    max-width: 640px;
}

.notes-list {
    display: flex;
    flex-direction: column;
    gap: 14px;
}

.note-item {
    padding: 16px;
    background: var(--color-bg);
    border-radius: var(--radius-md);
    border-left: 3px solid var(--color-primary);
    transition: all var(--transition-base);
}

.note-item:hover {
    box-shadow: var(--shadow-sm);
}

.note-item .note-context {
    font-size: 0.8125rem;
    color: var(--color-text-tertiary);
    font-style: italic;
    margin-bottom: 6px;
    padding: 6px 10px;
    background: var(--color-primary-light);
    border-radius: var(--radius-sm);
    line-height: 1.5;
}

.note-item .note-text {
    font-size: 0.9375rem;
    color: var(--color-text-primary);
    margin-bottom: 8px;
    line-height: 1.6;
}

.note-item .note-meta {
    font-size: 0.75rem;
    color: var(--color-text-tertiary);
    display: flex;
    align-items: center;
    justify-content: space-between;
}

.note-item .note-chapter {
    color: var(--color-primary);
    font-weight: 500;
}

.note-delete {
    color: var(--color-accent);
    cursor: pointer;
    font-size: 0.75rem;
    padding: 2px 6px;
    border-radius: 3px;
    transition: all var(--transition-fast);
}

.note-delete:hover {
    background: var(--color-accent-light);
}

.auth-tabs {
    display: flex;
    gap: 8px;
    margin-bottom: 24px;
    border-bottom: 2px solid var(--color-border);
    padding-bottom: 12px;
}

.auth-tab {
    flex: 1;
    padding: 10px 16px;
    border: none;
    background: none;
    color: var(--color-text-secondary);
    font-size: 0.9375rem;
    font-weight: 500;
    cursor: pointer;
    border-radius: var(--radius-sm);
    transition: all var(--transition-base);
}

.auth-tab:hover {
    background: var(--color-primary-light);
    color: var(--color-primary);
}

.auth-tab.active {
    background: var(--color-primary);
    color: white;
}

.auth-form {
    display: flex;
    flex-direction: column;
    gap: 16px;
}

.auth-form.hidden {
    display: none;
}

.auth-hint {
    text-align: center;
    font-size: 0.875rem;
    color: var(--color-text-secondary);
    margin-top: 8px;
}

.auth-hint a {
    color: var(--color-primary);
    text-decoration: none;
    font-weight: 500;
}

.auth-hint a:hover {
    text-decoration: underline;
}

/* ===== Auth Forgot Link ===== */
.auth-forgot {
    text-align: right;
    font-size: 0.8125rem;
    margin-top: -10px;
}

.auth-forgot a {
    color: var(--color-text-tertiary);
    text-decoration: none;
    transition: color var(--transition-fast);
}

.auth-forgot a:hover {
    color: var(--color-primary);
}

/* ===== Auth Form Footer ===== */
.auth-form-footer {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
    font-size: 0.875rem;
    color: var(--color-text-secondary);
}

.auth-footer-separator {
    color: var(--color-border);
}

/* ===== Verify Code Input ===== */
.verify-code-input {
    text-align: center;
    font-size: 1.5rem !important;
    letter-spacing: 8px;
    font-weight: 600;
}

.verify-code-input::placeholder {
    letter-spacing: 2px;
    font-size: 0.9375rem;
    font-weight: 400;
}

/* ===== Form Error ===== */
.form-error {
    font-size: 0.8125rem;
    color: var(--color-accent);
    margin-top: 4px;
    display: none;
}

.form-error.visible {
    display: block;
}

/* ===== Auth Back to Welcome Link ===== */
.auth-back-link {
    text-align: center;
    margin-top: 24px;
}

.auth-back-link a {
    display: inline-flex;
    align-items: center;
    gap: 4px;
    font-size: 0.875rem;
    color: var(--color-text-tertiary);
    transition: color var(--transition-fast);
}

.auth-back-link a:hover {
    color: var(--color-primary);
}

/* ===== Button Variants ===== */
.btn-text {
    color: var(--color-primary);
    padding: 4px 8px;
    font-size: 0.875rem;
    background: none;
    border: none;
    cursor: pointer;
    transition: color var(--transition-fast);
}

.btn-text:hover {
    color: var(--color-primary-dark);
    text-decoration: underline;
}

.btn-text:disabled {
    color: var(--color-text-tertiary);
    cursor: not-allowed;
    text-decoration: none;
}

/* ===== Button Loading State ===== */
.btn:disabled {
    opacity: 0.7;
    cursor: not-allowed;
    pointer-events: none;
}

.btn-loading {
    position: relative;
    color: transparent !important;
}

.btn-loading::after {
    content: '';
    position: absolute;
    width: 18px;
    height: 18px;
    border: 2px solid rgba(255, 255, 255, 0.3);
    border-top-color: #fff;
    border-radius: 50%;
    animation: spin 0.6s linear infinite;
}

@keyframes spin {
    to { transform: rotate(360deg); }
}

/* ===== Auth Form Transition ===== */
.auth-form,
.profile-form {
    animation: form-fade-in 0.25s ease;
}

@keyframes form-fade-in {
    from { opacity: 0; transform: translateY(8px); }
    to { opacity: 1; transform: translateY(0); }
}

/* ===== Auth Success Message ===== */
.auth-success-message {
    text-align: center;
    padding: 24px 0;
}

.auth-success-message .success-icon {
    width: 48px;
    height: 48px;
    margin: 0 auto 16px;
    color: #16a34a;
}

.auth-success-message p {
    color: var(--color-text-secondary);
    font-size: 0.9375rem;
    line-height: 1.6;
}

/* ===== Toast Notifications ===== */
.toast-container {
    position: fixed;
    top: 20px;
    right: 20px;
    z-index: 9999;
    display: flex;
    flex-direction: column;
    gap: 8px;
    pointer-events: none;
}

.toast {
    display: flex;
    align-items: center;
    gap: 10px;
    padding: 12px 20px;
    border-radius: var(--radius-md);
    box-shadow: var(--shadow-lg);
    font-size: 0.875rem;
    font-weight: 500;
    line-height: 1.5;
    max-width: 400px;
    pointer-events: auto;
    animation: toast-slide-in 0.3s ease, toast-fade-out 0.3s ease 3.7s forwards;
    cursor: default;
}

.toast-success {
    background: var(--color-success-light);
    color: var(--color-success);
    border: 1px solid var(--color-success);
}

.toast-error {
    background: var(--color-accent-light);
    color: var(--color-accent);
    border: 1px solid var(--color-accent);
}

.toast-info {
    background: var(--color-primary-light);
    color: var(--color-primary);
    border: 1px solid var(--color-primary);
}

.toast-warning {
    background: var(--color-warning-light);
    color: var(--color-warning);
    border: 1px solid var(--color-warning);
}

.toast-icon {
    flex-shrink: 0;
    width: 18px;
    height: 18px;
}

@keyframes toast-slide-in {
    from {
        transform: translateX(100%);
        opacity: 0;
    }
    to {
        transform: translateX(0);
        opacity: 1;
    }
}

@keyframes toast-fade-out {
    to {
        opacity: 0;
        transform: translateX(20px);
    }
}

/* ===========================================
   Learning Report — preview modal + print
   =========================================== */

.report-modal {
    z-index: 250;
}

.report-modal-content {
    max-width: 900px;
    width: calc(100% - 32px);
    max-height: 92vh;
    display: flex;
    flex-direction: column;
    background: #f4f4f0;
}

.report-modal-header {
    padding: 16px 20px;
    border-bottom: 1px solid var(--color-border);
    background: #fff;
    border-radius: var(--radius-xl) var(--radius-xl) 0 0;
}

.report-modal-actions {
    display: flex;
    align-items: center;
    gap: 12px;
}

.report-modal-body {
    overflow-y: auto;
    padding: 28px 0 36px;
    background: #f4f4f0;
    border-radius: 0 0 var(--radius-xl) var(--radius-xl);
}

/* The report itself — styled as a paper-like sheet */
.report-page {
    background: #fff;
    width: min(820px, calc(100% - 48px));
    margin: 0 auto;
    padding: 56px 64px 64px;
    color: #111;
    font-family: 'Noto Sans SC', -apple-system, BlinkMacSystemFont, 'Helvetica Neue', sans-serif;
    font-size: 14px;
    line-height: 1.7;
    box-shadow: 0 4px 24px rgba(15, 23, 42, 0.08);
    border-radius: 4px;
}

.report-page h1, .report-page h2, .report-page h3 {
    font-family: 'Noto Serif SC', Georgia, serif;
    color: #0f172a;
    font-weight: 600;
    line-height: 1.3;
    margin: 0;
}

/* Header */
.report-header {
    border-bottom: 2px solid #0f172a;
    padding-bottom: 28px;
    margin-bottom: 36px;
}

.report-header-top {
    display: flex;
    align-items: flex-start;
    justify-content: space-between;
    gap: 24px;
    margin-bottom: 28px;
}

.report-brand {
    display: flex;
    align-items: center;
    gap: 14px;
    color: var(--color-primary);
}

.report-brand-mark svg {
    width: 36px;
    height: 36px;
    display: block;
}

.report-brand-name {
    font-family: 'Noto Serif SC', Georgia, serif;
    font-size: 15px;
    font-weight: 700;
    color: #0f172a;
    letter-spacing: 0.5px;
}

.report-brand-sub {
    font-size: 11px;
    color: #64748b;
    margin-top: 2px;
}

.report-meta {
    text-align: right;
}

.report-meta-label {
    font-size: 10px;
    text-transform: uppercase;
    letter-spacing: 1.2px;
    color: #94a3b8;
    margin-bottom: 2px;
}

.report-meta-value {
    font-size: 12px;
    color: #475569;
    font-variant-numeric: tabular-nums;
}

.report-title {
    font-size: 36px;
    letter-spacing: 1.5px;
    margin-bottom: 20px;
}

.report-subject {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 8px 32px;
}

.report-subject-row {
    display: flex;
    gap: 12px;
    font-size: 13px;
    align-items: baseline;
}

.report-subject-k {
    color: #94a3b8;
    font-size: 11px;
    text-transform: uppercase;
    letter-spacing: 1px;
    min-width: 60px;
    white-space: nowrap;
}

.report-subject-v {
    color: #0f172a;
    font-weight: 500;
}

/* Sections */
.report-section {
    margin-bottom: 36px;
    page-break-inside: auto;
    break-inside: auto;
}

.report-section-title {
    font-size: 18px;
    margin-bottom: 18px;
    padding-left: 12px;
    border-left: 3px solid var(--color-primary);
    page-break-after: avoid;
    break-after: avoid;
}

.report-section-count {
    font-family: 'Noto Sans SC', sans-serif;
    font-weight: 400;
    font-size: 12px;
    color: #94a3b8;
    margin-left: 10px;
    letter-spacing: 0;
}

/* Overview cells */
.report-overview {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    border: 1px solid #e2e8f0;
    border-radius: 4px;
    overflow: hidden;
}

.report-overview-cell {
    padding: 18px 16px;
    text-align: center;
    border-right: 1px solid #e2e8f0;
}

.report-overview-cell:last-child {
    border-right: 0;
}

.report-overview-num {
    font-family: 'Noto Serif SC', Georgia, serif;
    font-size: 28px;
    font-weight: 700;
    color: var(--color-primary);
    line-height: 1.2;
    font-variant-numeric: tabular-nums;
}

.report-overview-unit {
    font-size: 12px;
    color: #94a3b8;
    font-weight: 400;
    margin-left: 2px;
}

.report-overview-label {
    font-size: 11px;
    color: #64748b;
    margin-top: 6px;
    letter-spacing: 0.5px;
}

.report-overview-sub {
    color: #94a3b8;
    margin-left: 2px;
}

/* Part / chapter list */
.report-part {
    margin-bottom: 16px;
    page-break-inside: avoid;
    break-inside: avoid;
}

.report-part-title {
    font-size: 14px;
    color: #475569;
    font-weight: 600;
    margin-bottom: 8px;
    padding-bottom: 4px;
    border-bottom: 1px dashed #cbd5e1;
}

.report-chapter-list {
    list-style: none;
    padding: 0;
    margin: 0;
}

.report-chapter-item {
    display: grid;
    grid-template-columns: 22px 1fr auto;
    align-items: baseline;
    gap: 10px;
    padding: 5px 0;
    font-size: 13px;
}

.report-chapter-mark {
    color: #cbd5e1;
    font-weight: 700;
    text-align: center;
}

.report-chapter-item.done .report-chapter-mark {
    color: var(--color-primary);
}

.report-chapter-title {
    color: #0f172a;
}

.report-chapter-item:not(.done) .report-chapter-title {
    color: #64748b;
}

.report-chapter-meta {
    font-size: 11px;
    color: #94a3b8;
    white-space: nowrap;
    font-variant-numeric: tabular-nums;
}

/* Goal path */
.report-goal-meta {
    background: #f8fafc;
    border-left: 3px solid var(--color-primary);
    padding: 12px 16px;
    margin-bottom: 16px;
    font-size: 13px;
    border-radius: 0 4px 4px 0;
}

.report-goal-meta .k {
    color: #64748b;
    font-weight: 600;
}

.report-goal-list {
    list-style: none;
    padding: 0;
    margin: 0;
    counter-reset: goal;
}

.report-goal-step {
    display: grid;
    grid-template-columns: 36px 1fr;
    gap: 16px;
    padding: 12px 0;
    border-bottom: 1px dashed #e2e8f0;
    page-break-inside: avoid;
    break-inside: avoid;
}

.report-goal-step:last-child {
    border-bottom: 0;
}

.report-goal-no {
    width: 32px;
    height: 32px;
    border-radius: 50%;
    background: var(--color-primary);
    color: #fff;
    display: flex;
    align-items: center;
    justify-content: center;
    font-family: 'Noto Serif SC', Georgia, serif;
    font-size: 14px;
    font-weight: 600;
}

.report-goal-head {
    font-size: 13px;
    font-weight: 600;
    color: #0f172a;
    margin-bottom: 4px;
}

.report-goal-line {
    font-size: 12.5px;
    color: #334155;
    margin-top: 4px;
}

.report-goal-line .k {
    color: var(--color-primary);
    font-weight: 600;
    margin-right: 4px;
}

/* Notes */
.report-notes-group {
    margin-bottom: 20px;
    page-break-inside: auto;
    break-inside: auto;
}

.report-notes-chapter {
    font-size: 13px;
    font-weight: 600;
    color: #475569;
    margin-bottom: 8px;
    padding-bottom: 4px;
    border-bottom: 1px dashed #cbd5e1;
}

.report-note {
    background: #f8fafc;
    border-left: 2px solid #cbd5e1;
    padding: 10px 14px;
    margin-bottom: 8px;
    font-size: 12.5px;
    border-radius: 0 4px 4px 0;
    page-break-inside: avoid;
    break-inside: avoid;
}

.report-note-context {
    color: #64748b;
    font-style: italic;
    margin-bottom: 6px;
    line-height: 1.55;
}

.report-note-body {
    color: #0f172a;
    line-height: 1.65;
}

.report-note-date {
    color: #94a3b8;
    font-size: 11px;
    margin-top: 6px;
    text-align: right;
}

/* Quiz */
.report-quiz-sub {
    font-size: 12px;
    color: #94a3b8;
    margin-bottom: 8px;
    letter-spacing: 0.5px;
}

.report-quiz-list {
    list-style: none;
    padding: 0;
    margin: 0;
}

.report-quiz-item {
    padding: 10px 14px;
    margin-bottom: 8px;
    border-left: 2px solid #cbd5e1;
    background: #f8fafc;
    font-size: 12.5px;
    border-radius: 0 4px 4px 0;
    page-break-inside: avoid;
    break-inside: avoid;
}

.report-quiz-item.wrong {
    border-left-color: var(--color-accent);
}

.report-quiz-meta {
    font-size: 11px;
    color: #94a3b8;
    margin-bottom: 4px;
}

.report-quiz-q {
    color: #0f172a;
    font-weight: 500;
    margin-bottom: 6px;
}

.report-quiz-a {
    color: #334155;
    margin-top: 2px;
}

.report-quiz-a .k {
    color: #64748b;
    font-weight: 600;
    margin-right: 4px;
}

.report-quiz-a .v.wrong {
    color: var(--color-accent);
    font-weight: 500;
}

.report-quiz-a .v.right {
    color: #15803d;
    font-weight: 500;
}

.report-empty {
    color: #94a3b8;
    font-size: 13px;
    text-align: center;
    padding: 12px 0;
}

/* Profile */
.report-profile {
    margin: 0;
    border: 1px solid #e2e8f0;
    border-radius: 4px;
    overflow: hidden;
}

.report-profile-row {
    display: grid;
    grid-template-columns: 140px 1fr;
    border-bottom: 1px solid #e2e8f0;
}

.report-profile-row:last-child {
    border-bottom: 0;
}

.report-profile-row dt {
    padding: 10px 14px;
    background: #f8fafc;
    font-size: 11px;
    color: #64748b;
    letter-spacing: 0.5px;
    text-transform: uppercase;
}

.report-profile-row dd {
    padding: 10px 14px;
    margin: 0;
    font-size: 13px;
    color: #0f172a;
}

/* Footer */
.report-footer {
    margin-top: 40px;
    padding-top: 16px;
    border-top: 1px solid #e2e8f0;
    text-align: center;
    color: #94a3b8;
    font-size: 11px;
    display: flex;
    justify-content: center;
    align-items: center;
    gap: 8px;
    flex-wrap: wrap;
}

/* Mobile preview */
@media (max-width: 720px) {
    .report-page {
        padding: 32px 24px 40px;
        width: calc(100% - 16px);
    }
    .report-overview {
        grid-template-columns: repeat(2, 1fr);
    }
    .report-overview-cell {
        border-right: 1px solid #e2e8f0;
        border-bottom: 1px solid #e2e8f0;
    }
    .report-overview-cell:nth-child(2n) {
        border-right: 0;
    }
    .report-overview-cell:nth-last-child(-n+2) {
        border-bottom: 0;
    }
    .report-subject {
        grid-template-columns: 1fr;
    }
    .report-title {
        font-size: 28px;
    }
}

/* ===== Print rules ===== */
@page {
    size: A4;
    margin: 18mm 16mm;
}

@media print {
    body.printing-report > *:not(#report-modal) {
        display: none !important;
    }
    body.printing-report #report-modal {
        position: static !important;
        display: block !important;
        padding: 0 !important;
        z-index: auto;
        background: #fff;
    }
    body.printing-report #report-modal .modal-overlay,
    body.printing-report .report-modal-header {
        display: none !important;
    }
    body.printing-report .report-modal-content {
        box-shadow: none !important;
        border-radius: 0 !important;
        max-width: none !important;
        width: 100% !important;
        max-height: none !important;
        background: #fff !important;
        animation: none !important;
    }
    body.printing-report .report-modal-body {
        background: #fff !important;
        padding: 0 !important;
        overflow: visible !important;
    }
    body.printing-report .report-page {
        box-shadow: none !important;
        border-radius: 0 !important;
        width: 100% !important;
        padding: 0 !important;
        margin: 0 !important;
        font-size: 11pt;
        line-height: 1.55;
    }
    body.printing-report .report-title {
        font-size: 28pt;
    }
    body.printing-report .report-section-title {
        font-size: 14pt;
    }
    body.printing-report .report-overview-num {
        font-size: 20pt;
    }
    /* page break hints */
    body.printing-report .report-section {
        page-break-inside: auto;
    }
    body.printing-report .report-section-title,
    body.printing-report .report-part-title,
    body.printing-report .report-notes-chapter,
    body.printing-report .report-goal-head {
        page-break-after: avoid;
        break-after: avoid;
    }
    body.printing-report .report-note,
    body.printing-report .report-quiz-item,
    body.printing-report .report-goal-step,
    body.printing-report .report-part {
        page-break-inside: avoid;
        break-inside: avoid;
    }
    /* Print color accuracy */
    body.printing-report .report-page,
    body.printing-report .report-page * {
        -webkit-print-color-adjust: exact;
        print-color-adjust: exact;
    }
}