/* ===== ZIXUE - Premium Design System ===== */

/* === Reset & Base === */
*, *::before, *::after { margin: 0; padding: 0; box-sizing: border-box; }

:root {
    /* Primary palette - Rich Indigo to Teal gradient */
    --primary: #6366f1;
    --primary-light: #818cf8;
    --primary-lighter: #a5b4fc;
    --primary-dark: #4f46e5;
    --primary-deeper: #3730a3;
    --accent: #14b8a6;
    --accent-light: #2dd4bf;
    --accent-dark: #0d9488;

    /* Backgrounds */
    --bg: #f8fafc;
    --bg-subtle: #f1f5f9;
    --card-bg: #ffffff;
    --card-bg-hover: #fefeff;

    /* Text */
    --text: #0f172a;
    --text-secondary: #334155;
    --text-light: #64748b;
    --text-lighter: #94a3b8;
    --text-faint: #cbd5e1;

    /* Borders */
    --border: #e2e8f0;
    --border-light: #f1f5f9;

    /* Status */
    --success: #10b981;
    --success-light: #34d399;
    --success-bg: #ecfdf5;
    --warning: #f59e0b;
    --warning-bg: #fffbeb;
    --danger: #ef4444;
    --danger-light: #f87171;
    --danger-bg: #fef2f2;
    --info: #3b82f6;
    --info-bg: #eff6ff;

    /* Radius */
    --radius-xs: 6px;
    --radius-sm: 10px;
    --radius: 14px;
    --radius-lg: 20px;
    --radius-xl: 28px;
    --radius-full: 9999px;

    /* Shadows - Layered for depth */
    --shadow-xs: 0 1px 2px rgba(0,0,0,0.04);
    --shadow-sm: 0 1px 3px rgba(0,0,0,0.05), 0 1px 2px rgba(0,0,0,0.03);
    --shadow: 0 2px 8px rgba(0,0,0,0.06), 0 1px 3px rgba(0,0,0,0.04);
    --shadow-md: 0 4px 12px -2px rgba(0,0,0,0.08), 0 2px 6px -2px rgba(0,0,0,0.04);
    --shadow-lg: 0 12px 24px -4px rgba(0,0,0,0.1), 0 4px 8px -2px rgba(0,0,0,0.04);
    --shadow-xl: 0 20px 40px -8px rgba(0,0,0,0.12), 0 8px 16px -4px rgba(0,0,0,0.06);
    --shadow-glow: 0 0 20px rgba(99,102,241,0.15);
    --shadow-glow-accent: 0 0 20px rgba(20,184,166,0.15);

    /* Transitions */
    --transition-fast: all 0.15s cubic-bezier(0.4, 0, 0.2, 1);
    --transition: all 0.25s cubic-bezier(0.4, 0, 0.2, 1);
    --transition-slow: all 0.4s cubic-bezier(0.4, 0, 0.2, 1);
    --transition-spring: all 0.5s cubic-bezier(0.34, 1.56, 0.64, 1);

    /* Gradients */
    --gradient-primary: linear-gradient(135deg, #6366f1, #14b8a6);
    --gradient-primary-soft: linear-gradient(135deg, #6366f1 0%, #818cf8 50%, #14b8a6 100%);
    --gradient-warm: linear-gradient(135deg, #f59e0b, #ef4444);
    --gradient-cool: linear-gradient(135deg, #3b82f6, #6366f1);
    --gradient-bg: linear-gradient(180deg, #f0f4ff 0%, #f8fafc 40%, #ffffff 100%);

    /* Glass */
    --glass-bg: rgba(255,255,255,0.7);
    --glass-border: rgba(255,255,255,0.3);
    --glass-blur: blur(20px);
}

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', 'PingFang SC', 'Hiragino Sans GB', 'Microsoft YaHei', sans-serif;
    background: var(--bg);
    color: var(--text);
    line-height: 1.6;
    min-height: 100vh;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

/* Smooth scrolling */
html { scroll-behavior: smooth; }

a { text-decoration: none; color: inherit; }
ul { list-style: none; }
button { cursor: pointer; border: none; font-family: inherit; }
input, textarea, select { font-family: inherit; }

/* Selection color */
::selection {
    background: rgba(99,102,241,0.15);
    color: var(--primary-dark);
}

/* Focus ring */
:focus-visible {
    outline: 2px solid var(--primary-light);
    outline-offset: 2px;
    border-radius: var(--radius-xs);
}

/* === Layout === */
.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 24px;
}

/* === Header === */
.header {
    background: var(--glass-bg);
    border-bottom: 1px solid var(--glass-border);
    position: sticky;
    top: 0;
    z-index: 100;
    backdrop-filter: var(--glass-blur);
    -webkit-backdrop-filter: var(--glass-blur);
    transition: var(--transition);
}

.header .container {
    display: flex;
    align-items: center;
    justify-content: space-between;
    height: 64px;
}

.logo {
    display: flex;
    align-items: center;
    gap: 10px;
    font-size: 20px;
    font-weight: 800;
    color: var(--text);
    letter-spacing: -0.02em;
    transition: var(--transition);
}

.logo:hover { opacity: 0.85; }

.logo-icon {
    width: 38px;
    height: 38px;
    border-radius: var(--radius-sm);
    display: flex;
    align-items: center;
    justify-content: center;
    box-shadow: 0 2px 8px rgba(99,102,241,0.3);
    transition: var(--transition-spring);
    overflow: hidden;
    position: relative;
    background: var(--gradient-primary);
}

.logo-icon svg {
    width: 22px;
    height: 22px;
    position: relative;
    z-index: 1;
}

.logo-icon::after {
    content: '';
    position: absolute;
    top: -50%;
    left: -50%;
    width: 200%;
    height: 200%;
    background: radial-gradient(circle at 30% 20%, rgba(255,255,255,0.2) 0%, transparent 50%);
    pointer-events: none;
}

.logo:hover .logo-icon { transform: scale(1.05) rotate(-2deg); box-shadow: 0 4px 16px rgba(99,102,241,0.4); }

/* ===== 分享按钮（quiz-header 中） ===== */
.quiz-header-actions {
    display: flex;
    align-items: center;
    gap: 8px;
    flex-wrap: wrap;
}

.btn-share-header {
    display: inline-flex;
    align-items: center;
    gap: 6px;
    padding: 8px 16px;
    border-radius: var(--radius-sm);
    font-size: 13px;
    font-weight: 600;
    color: var(--primary);
    background: rgba(99,102,241,0.06);
    border: 1px solid rgba(99,102,241,0.12);
    transition: var(--transition);
    cursor: pointer;
}
.btn-share-header:hover {
    background: rgba(99,102,241,0.12);
    border-color: rgba(99,102,241,0.25);
    transform: translateY(-1px);
}
.btn-share-header:disabled { opacity: 0.5; cursor: not-allowed; }

.btn-clear-mistakes {
    display: inline-flex;
    align-items: center;
    gap: 6px;
    padding: 8px 16px;
    border-radius: var(--radius-sm);
    font-size: 13px;
    font-weight: 600;
    color: var(--danger);
    background: rgba(239,68,68,0.06);
    border: 1px solid rgba(239,68,68,0.12);
    transition: var(--transition);
    cursor: pointer;
}
.btn-clear-mistakes:hover {
    background: rgba(239,68,68,0.12);
    border-color: rgba(239,68,68,0.25);
    transform: translateY(-1px);
}
.btn-clear-mistakes:disabled { opacity: 0.5; cursor: not-allowed; }

.share-spinner {
    display: inline-block;
    width: 14px; height: 14px;
    border: 2px solid rgba(99,102,241,0.2);
    border-top-color: var(--primary);
    border-radius: 50%;
    animation: spin 0.6s linear infinite;
}
@keyframes spin { to { transform: rotate(360deg); } }

/* ===== 分享领取页面 ===== */
.share-card {
    background: var(--card-bg);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-xl);
    padding: 40px 36px;
    border: 1px solid var(--glass-border);
}
.share-header { text-align: center; margin-bottom: 28px; }
.share-type-badge {
    display: inline-block;
    padding: 4px 14px;
    border-radius: var(--radius-full);
    font-size: 12px;
    font-weight: 700;
    color: var(--primary);
    background: rgba(99,102,241,0.08);
    margin-bottom: 14px;
    letter-spacing: 0.02em;
}
.share-card-title {
    font-size: 24px;
    font-weight: 800;
    color: var(--text);
    letter-spacing: -0.02em;
    margin-bottom: 14px;
    line-height: 1.3;
}
.share-meta {
    display: flex;
    flex-wrap: wrap;
    gap: 8px 16px;
    justify-content: center;
}
.share-meta-item {
    display: inline-flex;
    align-items: center;
    gap: 5px;
    font-size: 13px;
    color: var(--text-light);
}
.share-meta-item svg { color: var(--text-lighter); }

.share-preview {
    background: var(--bg);
    border-radius: var(--radius);
    padding: 20px;
    margin-bottom: 24px;
}
.share-preview-title {
    font-size: 13px;
    font-weight: 700;
    color: var(--text-light);
    margin-bottom: 12px;
    text-transform: uppercase;
    letter-spacing: 0.05em;
}
.share-preview-item {
    display: flex;
    gap: 10px;
    padding: 10px 0;
    border-bottom: 1px solid var(--border-light);
}
.share-preview-item:last-child { border-bottom: none; }
.share-preview-num {
    width: 22px; height: 22px;
    border-radius: 50%;
    background: rgba(99,102,241,0.08);
    color: var(--primary);
    font-size: 12px;
    font-weight: 700;
    display: flex;
    align-items: center;
    justify-content: center;
    flex-shrink: 0;
}
.share-preview-content { flex: 1; min-width: 0; }
.share-preview-text {
    font-size: 13px;
    color: var(--text-secondary);
    line-height: 1.5;
    margin-bottom: 4px;
    overflow: hidden;
    text-overflow: ellipsis;
    display: -webkit-box;
    -webkit-line-clamp: 2;
    -webkit-box-orient: vertical;
}
.share-preview-type {
    font-size: 11px;
    color: var(--text-lighter);
    padding: 1px 8px;
    border-radius: var(--radius-full);
    background: var(--card-bg);
    border: 1px solid var(--border);
}

.share-actions {
    text-align: center;
    margin-bottom: 20px;
}
.share-claim-btn {
    width: auto !important;
    padding: 14px 40px !important;
    font-size: 15px !important;
    font-weight: 700 !important;
}
.share-owner-notice {
    display: inline-block;
    padding: 10px 20px;
    border-radius: var(--radius-sm);
    background: var(--info-bg);
    color: var(--info);
    font-size: 13px;
    font-weight: 500;
}
.share-claimed-notice {
    display: inline-block;
    padding: 10px 20px;
    border-radius: var(--radius-sm);
    background: var(--success-bg);
    color: var(--success);
    font-size: 13px;
    font-weight: 500;
    margin-bottom: 12px;
}
.share-footer {
    text-align: center;
    padding-top: 16px;
    border-top: 1px solid var(--border-light);
}
.share-footer p {
    font-size: 12px;
    color: var(--text-lighter);
}

.share-icon-lock {
    width: 64px; height: 64px;
    border-radius: 16px;
    background: var(--bg-subtle);
    display: flex;
    align-items: center;
    justify-content: center;
    color: var(--text-light);
    margin: 0 auto 20px;
}
.share-title {
    font-size: 22px;
    font-weight: 800;
    color: var(--text);
    text-align: center;
    margin-bottom: 8px;
    letter-spacing: -0.01em;
}
.share-desc {
    font-size: 14px;
    color: var(--text-light);
    text-align: center;
    line-height: 1.6;
}
.share-success-icon {
    width: 72px; height: 72px;
    border-radius: 50%;
    background: var(--success-bg);
    color: var(--success);
    display: flex;
    align-items: center;
    justify-content: center;
    margin: 0 auto 20px;
    animation: scaleIn 0.4s cubic-bezier(0.34,1.56,0.64,1);
}
@keyframes scaleIn { from { transform: scale(0); } to { transform: scale(1); } }

/* ===== 错题集入口 Banner ===== */
.mistakes-banner {
    display: flex;
    align-items: center;
    justify-content: space-between;
    background: linear-gradient(135deg, #fef2f2 0%, #fff7ed 100%);
    border: 1px solid rgba(239,68,68,0.12);
    border-radius: var(--radius-sm);
    padding: 10px 18px;
    text-decoration: none;
    transition: var(--transition);
    position: relative;
    overflow: hidden;
    max-width: 420px;
    margin: 0 auto;
}
.mistakes-banner:hover {
    border-color: rgba(239,68,68,0.25);
    box-shadow: 0 2px 12px rgba(239,68,68,0.06);
}
.mistakes-banner::before {
    content: '';
    position: absolute;
    top: 0; left: 0; bottom: 0;
    width: 3px;
    background: linear-gradient(180deg, #ef4444, #f97316);
}
.mistakes-banner-left {
    display: flex;
    align-items: center;
    gap: 10px;
}
.mistakes-banner-icon {
    width: 32px; height: 32px;
    border-radius: 8px;
    background: linear-gradient(135deg, #ef4444, #f97316);
    display: flex;
    align-items: center;
    justify-content: center;
    color: white;
    flex-shrink: 0;
}
.mistakes-banner-text {
    display: flex;
    flex-direction: column;
    gap: 2px;
}
.mistakes-banner-title {
    font-size: 14px;
    font-weight: 700;
    color: var(--text);
}
.mistakes-banner-sub {
    font-size: 12px;
    color: var(--text-light);
}
.mistakes-banner-right {
    display: flex;
    align-items: center;
    gap: 8px;
}
.mistakes-banner-count {
    font-size: 20px;
    font-weight: 800;
    color: #ef4444;
    line-height: 1;
}
.mistakes-banner-arrow {
    color: var(--text-lighter);
    font-size: 14px;
    transition: var(--transition);
}
.mistakes-banner:hover .mistakes-banner-arrow {
    color: #ef4444;
    transform: translateX(3px);
}

.nav {
    display: flex;
    align-items: center;
    gap: 4px;
}

.nav a {
    padding: 8px 16px;
    border-radius: var(--radius-sm);
    color: var(--text-light);
    font-size: 14px;
    font-weight: 500;
    transition: var(--transition);
    position: relative;
}

.nav a:hover {
    color: var(--primary);
    background: rgba(99,102,241,0.06);
}

.nav .btn-login {
    background: var(--gradient-primary);
    color: white;
    padding: 8px 22px;
    font-weight: 600;
    box-shadow: 0 2px 8px rgba(99,102,241,0.25);
}

.nav .btn-login:hover {
    box-shadow: 0 4px 16px rgba(99,102,241,0.35);
    transform: translateY(-1px);
    color: white;
}

.nav .user-info {
    display: flex;
    align-items: center;
    gap: 12px;
}

.nav .user-avatar {
    width: 34px;
    height: 34px;
    border-radius: var(--radius-full);
    background: var(--gradient-primary);
    color: white;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 14px;
    font-weight: 600;
    box-shadow: 0 2px 6px rgba(99,102,241,0.25);
}

/* === Hero Section === */
.hero {
    text-align: center;
    padding: 72px 24px 48px;
    position: relative;
    overflow: hidden;
}

.hero::before {
    content: '';
    position: absolute;
    top: -60%;
    left: 50%;
    transform: translateX(-50%);
    width: 800px;
    height: 600px;
    background: radial-gradient(ellipse, rgba(99,102,241,0.08) 0%, rgba(20,184,166,0.04) 40%, transparent 70%);
    pointer-events: none;
}

.hero h1 {
    font-size: 40px;
    font-weight: 900;
    background: var(--gradient-primary-soft);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    margin-bottom: 14px;
    letter-spacing: -0.03em;
    line-height: 1.2;
    position: relative;
}

.hero p {
    font-size: 17px;
    color: var(--text-light);
    max-width: 560px;
    margin: 0 auto;
    line-height: 1.7;
    position: relative;
}

/* === Grade Tabs === */
.grade-tabs {
    display: flex;
    justify-content: center;
    gap: 8px;
    margin-bottom: 40px;
    flex-wrap: wrap;
}

.grade-tab {
    padding: 10px 22px;
    border-radius: var(--radius-full);
    font-size: 14px;
    font-weight: 500;
    color: var(--text-light);
    background: var(--card-bg);
    border: 1px solid var(--border);
    transition: var(--transition);
    cursor: pointer;
}

.grade-tab:hover { border-color: var(--primary-light); color: var(--primary); transform: translateY(-1px); }

.grade-tab.active {
    background: var(--gradient-primary);
    color: white;
    border-color: transparent;
    box-shadow: 0 4px 12px rgba(99,102,241,0.25);
}

/* === Subject Grid === */
.subject-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
    gap: 20px;
    padding-bottom: 60px;
}

.subject-card {
    background: var(--card-bg);
    border-radius: var(--radius);
    padding: 26px;
    box-shadow: var(--shadow);
    transition: var(--transition);
    border: 1px solid var(--border-light);
    overflow: hidden;
    position: relative;
}

.subject-card::before {
    content: '';
    position: absolute;
    top: 0; left: 0; right: 0;
    height: 3px;
    background: var(--gradient-primary);
    opacity: 0;
    transition: var(--transition);
}

.subject-card:hover {
    transform: translateY(-4px);
    box-shadow: var(--shadow-lg);
    border-color: rgba(99,102,241,0.15);
}

.subject-card:hover::before { opacity: 1; }

.subject-header {
    display: flex;
    align-items: center;
    gap: 14px;
    margin-bottom: 18px;
}

.subject-icon {
    width: 52px;
    height: 52px;
    border-radius: var(--radius);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 26px;
    background: color-mix(in srgb, var(--card-color, var(--primary)) 10%, transparent);
    transition: var(--transition);
}

.subject-card:hover .subject-icon {
    transform: scale(1.08);
}

.subject-name {
    font-size: 18px;
    font-weight: 700;
    color: var(--text);
    letter-spacing: -0.01em;
}

.grade-list {
    display: flex;
    flex-direction: column;
    gap: 6px;
}

.grade-link {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 10px 14px;
    border-radius: var(--radius-sm);
    background: var(--bg);
    transition: var(--transition);
    font-size: 14px;
}

.grade-link:hover {
    background: color-mix(in srgb, var(--card-color, var(--primary)) 8%, transparent);
    transform: translateX(3px);
}

.grade-link .grade-name { font-weight: 500; color: var(--text-secondary); }
.grade-link .question-count {
    font-size: 12px;
    color: var(--text-lighter);
    background: var(--card-bg);
    padding: 2px 10px;
    border-radius: var(--radius-full);
    font-weight: 500;
}

.grade-link.disabled {
    opacity: 0.5;
    pointer-events: none;
}

/* === Auth Pages === */
.auth-page {
    min-height: calc(100vh - 64px);
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 40px 24px;
    position: relative;
}

.auth-page::before {
    content: '';
    position: absolute;
    top: 0; left: 0; right: 0; bottom: 0;
    background: var(--gradient-bg);
    pointer-events: none;
}

.auth-card {
    background: var(--card-bg);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-xl);
    padding: 44px;
    width: 100%;
    max-width: 420px;
    border: 1px solid var(--glass-border);
    position: relative;
    animation: cardEntry 0.5s cubic-bezier(0.34, 1.56, 0.64, 1);
}

@keyframes cardEntry {
    from { opacity: 0; transform: translateY(20px) scale(0.98); }
    to { opacity: 1; transform: translateY(0) scale(1); }
}

.auth-card h2 {
    font-size: 26px;
    font-weight: 800;
    margin-bottom: 8px;
    text-align: center;
    letter-spacing: -0.02em;
    color: var(--text);
}

.auth-card .subtitle {
    text-align: center;
    color: var(--text-light);
    font-size: 14px;
    margin-bottom: 32px;
}

.form-group {
    margin-bottom: 20px;
}

.form-group label {
    display: block;
    font-size: 13px;
    font-weight: 600;
    color: var(--text-secondary);
    margin-bottom: 8px;
    letter-spacing: 0.01em;
}

.form-group input,
.form-group select,
.form-group textarea {
    width: 100%;
    padding: 12px 16px;
    border: 1.5px solid var(--border);
    border-radius: var(--radius-sm);
    font-size: 14px;
    transition: var(--transition);
    background: var(--card-bg);
    color: var(--text);
}

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

.form-group input:hover,
.form-group select:hover,
.form-group textarea:hover {
    border-color: var(--text-faint);
}

.form-group input:focus,
.form-group select:focus,
.form-group textarea:focus {
    outline: none;
    border-color: var(--primary);
    box-shadow: 0 0 0 3px rgba(99,102,241,0.1);
}

.form-group textarea {
    resize: vertical;
    min-height: 80px;
}

/* Buttons */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: 11px 24px;
    border-radius: var(--radius-sm);
    font-size: 14px;
    font-weight: 600;
    transition: var(--transition);
    border: none;
    position: relative;
    overflow: hidden;
}

.btn::after {
    content: '';
    position: absolute;
    inset: 0;
    background: linear-gradient(180deg, rgba(255,255,255,0.1) 0%, transparent 100%);
    pointer-events: none;
}

.btn-primary {
    background: var(--gradient-primary);
    color: white;
    width: 100%;
    box-shadow: 0 2px 8px rgba(99,102,241,0.25);
}

.btn-primary:hover {
    box-shadow: 0 4px 16px rgba(99,102,241,0.35);
    transform: translateY(-1px);
}

.btn-primary:active {
    transform: translateY(0);
    box-shadow: 0 1px 4px rgba(99,102,241,0.2);
}

.btn-secondary {
    background: var(--bg);
    color: var(--text-secondary);
    border: 1px solid var(--border);
}

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

.btn-danger {
    background: var(--danger);
    color: white;
    box-shadow: 0 2px 8px rgba(239,68,68,0.25);
}

.btn-danger:hover { background: var(--danger-light); }

.btn-success {
    background: var(--success);
    color: white;
    box-shadow: 0 2px 8px rgba(16,185,129,0.25);
}

.btn-success:hover { background: var(--success-light); }

.auth-footer {
    text-align: center;
    margin-top: 24px;
    font-size: 14px;
    color: var(--text-light);
}

.auth-footer a { color: var(--primary); font-weight: 600; }
.auth-footer a:hover { color: var(--primary-dark); }

.forgot-link {
    text-align: right;
    margin-bottom: 8px;
    font-size: 13px;
}
.forgot-link a { color: var(--text-light); text-decoration: none; }
.forgot-link a:hover { color: var(--primary); text-decoration: underline; }

/* === Quiz Page === */
.quiz-container {
    max-width: 800px;
    margin: 0 auto;
    padding: 32px 24px 80px;
}

.quiz-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    margin-bottom: 24px;
}

.quiz-header .back-btn {
    display: flex;
    align-items: center;
    gap: 6px;
    color: var(--text-light);
    font-size: 14px;
    font-weight: 500;
    transition: var(--transition);
    padding: 6px 12px;
    border-radius: var(--radius-sm);
}

.quiz-header .back-btn:hover { color: var(--primary); background: rgba(99,102,241,0.06); }

.quiz-title {
    font-size: 20px;
    font-weight: 700;
    color: var(--text);
    letter-spacing: -0.01em;
}

.quiz-progress {
    margin-bottom: 24px;
}

.progress-bar {
    height: 8px;
    background: var(--bg-subtle);
    border-radius: var(--radius-full);
    overflow: hidden;
    position: relative;
}

.progress-bar::before {
    content: '';
    position: absolute;
    inset: 0;
    background: var(--border-light);
    border-radius: var(--radius-full);
}

.progress-bar .fill {
    height: 100%;
    background: var(--gradient-primary);
    transition: width 0.5s cubic-bezier(0.4, 0, 0.2, 1);
    border-radius: var(--radius-full);
    position: relative;
}

.progress-bar .fill::after {
    content: '';
    position: absolute;
    top: 0; left: 0; right: 0; bottom: 0;
    background: linear-gradient(90deg, transparent, rgba(255,255,255,0.3), transparent);
    animation: progressShimmer 2s infinite;
}

@keyframes progressShimmer {
    0% { transform: translateX(-100%); }
    100% { transform: translateX(100%); }
}

.progress-text {
    display: flex;
    justify-content: space-between;
    margin-top: 10px;
    font-size: 13px;
    color: var(--text-light);
    font-weight: 500;
}

.question-card {
    background: var(--card-bg);
    border-radius: var(--radius);
    box-shadow: var(--shadow-md);
    padding: 36px;
    border: 1px solid var(--border-light);
    margin-bottom: 20px;
    animation: questionEnter 0.35s cubic-bezier(0.34, 1.56, 0.64, 1);
}

@keyframes questionEnter {
    from { opacity: 0; transform: translateX(12px); }
    to { opacity: 1; transform: translateX(0); }
}

.question-meta {
    display: flex;
    align-items: center;
    gap: 8px;
    margin-bottom: 18px;
    flex-wrap: wrap;
}

.badge {
    display: inline-flex;
    align-items: center;
    padding: 4px 12px;
    border-radius: var(--radius-full);
    font-size: 12px;
    font-weight: 600;
    letter-spacing: 0.02em;
}

.badge-single { background: rgba(99,102,241,0.08); color: var(--primary); }
.badge-multiple { background: var(--warning-bg); color: var(--warning); }
.badge-source { background: var(--bg-subtle); color: var(--text-light); }

.question-content {
    font-size: 17px;
    line-height: 1.8;
    margin-bottom: 28px;
    color: var(--text);
    font-weight: 500;
}

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

.option-item {
    display: flex;
    align-items: flex-start;
    gap: 14px;
    padding: 16px 18px;
    border: 2px solid var(--border-light);
    border-radius: var(--radius);
    cursor: pointer;
    transition: var(--transition);
    background: var(--card-bg);
}

.option-item:hover {
    border-color: var(--primary-lighter);
    background: rgba(99,102,241,0.02);
    transform: translateX(2px);
}

.option-item.selected {
    border-color: var(--primary);
    background: rgba(99,102,241,0.04);
    box-shadow: 0 0 0 3px rgba(99,102,241,0.08);
}

.option-item.correct {
    border-color: var(--success);
    background: var(--success-bg);
    box-shadow: 0 0 0 3px rgba(16,185,129,0.1);
}

.option-item.wrong {
    border-color: var(--danger);
    background: var(--danger-bg);
    box-shadow: 0 0 0 3px rgba(239,68,68,0.08);
}

.option-label {
    width: 30px;
    height: 30px;
    min-width: 30px;
    border-radius: var(--radius-full);
    border: 2px solid var(--border);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 13px;
    font-weight: 700;
    color: var(--text-light);
    transition: var(--transition);
    background: var(--card-bg);
}

.option-item.selected .option-label {
    border-color: var(--primary);
    background: var(--gradient-primary);
    color: white;
    box-shadow: 0 2px 6px rgba(99,102,241,0.3);
}

.option-item.correct .option-label {
    border-color: var(--success);
    background: var(--success);
    color: white;
    box-shadow: 0 2px 6px rgba(16,185,129,0.3);
}

.option-item.wrong .option-label {
    border-color: var(--danger);
    background: var(--danger);
    color: white;
    box-shadow: 0 2px 6px rgba(239,68,68,0.3);
}

.option-text {
    flex: 1;
    font-size: 15px;
    line-height: 1.6;
    padding-top: 3px;
    color: var(--text-secondary);
}

/* Explanation */
.explanation-box {
    margin-top: 24px;
    padding: 20px;
    background: linear-gradient(135deg, rgba(99,102,241,0.04), rgba(20,184,166,0.04));
    border-left: 3px solid var(--primary);
    border-radius: 0 var(--radius) var(--radius) 0;
    display: none;
}

.explanation-box.show {
    display: block;
    animation: explanationReveal 0.35s ease;
}

@keyframes explanationReveal {
    from { opacity: 0; max-height: 0; margin-top: 0; }
    to { opacity: 1; max-height: 200px; margin-top: 24px; }
}

.explanation-box h4 {
    font-size: 13px;
    color: var(--primary);
    margin-bottom: 8px;
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

.explanation-box p {
    font-size: 14px;
    color: var(--text-secondary);
    line-height: 1.8;
}

/* Quiz actions */
.quiz-actions {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 12px;
    margin-top: 28px;
}

.mark-buttons {
    display: flex;
    gap: 8px;
}

.btn-mark {
    padding: 10px 18px;
    border-radius: var(--radius-sm);
    font-size: 13px;
    font-weight: 600;
    transition: var(--transition);
    display: flex;
    align-items: center;
    gap: 6px;
}

.btn-mark-mastered {
    background: var(--success-bg);
    color: var(--success);
    border: 1px solid transparent;
}

.btn-mark-mastered:hover {
    background: rgba(16,185,129,0.15);
    transform: translateY(-1px);
}

.btn-mark-mastered.active {
    background: var(--success);
    color: white;
    box-shadow: 0 2px 8px rgba(16,185,129,0.3);
}

.btn-mark-weak {
    background: var(--danger-bg);
    color: var(--danger);
    border: 1px solid transparent;
}

.btn-mark-weak:hover {
    background: rgba(239,68,68,0.12);
    transform: translateY(-1px);
}

.btn-mark-weak.active {
    background: var(--danger);
    color: white;
    box-shadow: 0 2px 8px rgba(239,68,68,0.3);
}

.btn-next {
    background: var(--gradient-primary);
    color: white;
    padding: 12px 32px;
    border-radius: var(--radius-sm);
    font-size: 14px;
    font-weight: 700;
    transition: var(--transition);
    box-shadow: 0 2px 8px rgba(99,102,241,0.25);
    letter-spacing: 0.01em;
}

.btn-next:hover:not(:disabled) {
    box-shadow: 0 4px 16px rgba(99,102,241,0.35);
    transform: translateY(-1px);
}

.btn-next:disabled { opacity: 0.4; cursor: not-allowed; box-shadow: none; }

/* Quiz result */
.quiz-result {
    text-align: center;
    padding: 64px 24px;
    animation: resultReveal 0.6s cubic-bezier(0.34, 1.56, 0.64, 1);
}

@keyframes resultReveal {
    from { opacity: 0; transform: scale(0.95); }
    to { opacity: 1; transform: scale(1); }
}

.quiz-result .score {
    font-size: 56px;
    font-weight: 900;
    background: var(--gradient-primary-soft);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    letter-spacing: -0.03em;
}

.quiz-result .score-label {
    font-size: 17px;
    color: var(--text-light);
    margin-top: 10px;
    font-weight: 500;
}

.quiz-result-actions {
    display: flex;
    gap: 12px;
    justify-content: center;
    margin-top: 36px;
}

/* === Admin === */
.admin-layout {
    display: flex;
    min-height: calc(100vh - 64px);
}

.admin-sidebar {
    width: 240px;
    background: var(--card-bg);
    border-right: 1px solid var(--border-light);
    padding: 24px 0;
    flex-shrink: 0;
}

.admin-sidebar a {
    display: flex;
    align-items: center;
    gap: 12px;
    padding: 12px 24px;
    color: var(--text-light);
    font-size: 14px;
    font-weight: 500;
    transition: var(--transition);
    border-left: 3px solid transparent;
    margin: 2px 0;
}

.admin-sidebar a:hover {
    background: var(--bg);
    color: var(--text);
}

.admin-sidebar a.active {
    color: var(--primary);
    border-left-color: var(--primary);
    background: rgba(99,102,241,0.04);
    font-weight: 600;
}

.admin-content {
    flex: 1;
    padding: 36px;
    overflow-x: auto;
    background: var(--bg);
}

.admin-page-title {
    font-size: 24px;
    font-weight: 800;
    margin-bottom: 28px;
    letter-spacing: -0.02em;
    color: var(--text);
}

/* Stats grid */
.stats-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 20px;
    margin-bottom: 32px;
}

.stat-card {
    background: var(--card-bg);
    border-radius: var(--radius);
    padding: 24px;
    box-shadow: var(--shadow);
    border: 1px solid var(--border-light);
    transition: var(--transition);
}

.stat-card:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
}

.stat-card .stat-icon {
    width: 46px;
    height: 46px;
    border-radius: var(--radius-sm);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 22px;
    margin-bottom: 14px;
}

.stat-card .stat-value {
    font-size: 30px;
    font-weight: 800;
    color: var(--text);
    letter-spacing: -0.02em;
}

.stat-card .stat-label {
    font-size: 13px;
    color: var(--text-light);
    margin-top: 4px;
    font-weight: 500;
}

/* Table */
.data-table {
    width: 100%;
    background: var(--card-bg);
    border-radius: var(--radius);
    box-shadow: var(--shadow);
    border: 1px solid var(--border-light);
    overflow: hidden;
}

.data-table table {
    width: 100%;
    border-collapse: collapse;
}

.data-table th {
    text-align: left;
    padding: 14px 18px;
    font-size: 12px;
    font-weight: 700;
    color: var(--text-light);
    background: var(--bg-subtle);
    border-bottom: 1px solid var(--border);
    white-space: nowrap;
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

.data-table td {
    padding: 14px 18px;
    font-size: 14px;
    border-bottom: 1px solid var(--border-light);
    color: var(--text-secondary);
}

.data-table tr:last-child td { border-bottom: none; }
.data-table tr:hover td { background: rgba(99,102,241,0.02); }

.data-table .actions {
    display: flex;
    gap: 6px;
}

.data-table .actions a,
.data-table .actions button {
    padding: 5px 14px;
    border-radius: var(--radius-xs);
    font-size: 13px;
    font-weight: 500;
    transition: var(--transition);
}

.action-edit { background: rgba(99,102,241,0.08); color: var(--primary); }
.action-edit:hover { background: rgba(99,102,241,0.15); }
.action-delete { background: var(--danger-bg); color: var(--danger); }
.action-delete:hover { background: rgba(239,68,68,0.15); }

/* Filters bar */
.filters-bar {
    display: flex;
    gap: 12px;
    margin-bottom: 24px;
    flex-wrap: wrap;
    align-items: center;
}

.filters-bar select,
.filters-bar input {
    padding: 10px 14px;
    border: 1.5px solid var(--border);
    border-radius: var(--radius-sm);
    font-size: 14px;
    background: var(--card-bg);
    transition: var(--transition);
}

.filters-bar select:focus,
.filters-bar input:focus {
    outline: none;
    border-color: var(--primary);
    box-shadow: 0 0 0 3px rgba(99,102,241,0.08);
}

.filters-bar .btn-search {
    padding: 10px 20px;
    background: var(--gradient-primary);
    color: white;
    border-radius: var(--radius-sm);
    font-size: 14px;
    font-weight: 600;
    box-shadow: 0 2px 8px rgba(99,102,241,0.2);
}

.filters-bar .btn-add {
    margin-left: auto;
    padding: 10px 22px;
    background: var(--gradient-primary);
    color: white;
    border-radius: var(--radius-sm);
    font-size: 14px;
    font-weight: 600;
    display: flex;
    align-items: center;
    gap: 6px;
    box-shadow: 0 2px 8px rgba(99,102,241,0.2);
}

/* Pagination */
.pagination {
    display: flex;
    gap: 6px;
    justify-content: center;
    margin-top: 28px;
}

.pagination a {
    padding: 8px 14px;
    border-radius: var(--radius-sm);
    font-size: 13px;
    font-weight: 500;
    color: var(--text-light);
    background: var(--card-bg);
    border: 1px solid var(--border);
    transition: var(--transition);
}

.pagination a:hover { border-color: var(--primary-light); color: var(--primary); }
.pagination a.active {
    background: var(--gradient-primary);
    color: white;
    border-color: transparent;
    box-shadow: 0 2px 6px rgba(99,102,241,0.2);
}

/* Form page */
.form-card {
    background: var(--card-bg);
    border-radius: var(--radius);
    box-shadow: var(--shadow);
    padding: 36px;
    border: 1px solid var(--border-light);
    max-width: 800px;
}

.option-row {
    display: flex;
    align-items: center;
    gap: 8px;
    margin-bottom: 8px;
}

.option-row .option-letter {
    width: 34px;
    height: 34px;
    min-width: 34px;
    border-radius: var(--radius-xs);
    background: var(--bg-subtle);
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: 700;
    font-size: 13px;
    color: var(--text-light);
}

.option-row input {
    flex: 1;
    padding: 10px 14px;
    border: 1.5px solid var(--border);
    border-radius: var(--radius-sm);
    font-size: 14px;
    transition: var(--transition);
}

.option-row input:focus {
    outline: none;
    border-color: var(--primary);
    box-shadow: 0 0 0 3px rgba(99,102,241,0.08);
}

.option-row .option-correct {
    width: 34px;
    height: 34px;
    min-width: 34px;
    border-radius: var(--radius-xs);
    border: 2px solid var(--border);
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    transition: var(--transition);
    font-size: 14px;
    color: transparent;
}

.option-row .option-correct:hover { border-color: var(--success-light); }

.option-row .option-correct.checked {
    background: var(--success);
    border-color: var(--success);
    color: white;
}

.option-row .btn-remove {
    width: 34px;
    height: 34px;
    min-width: 34px;
    border-radius: var(--radius-xs);
    background: var(--danger-bg);
    color: var(--danger);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 16px;
    transition: var(--transition);
}

.option-row .btn-remove:hover { background: rgba(239,68,68,0.15); }

.form-actions {
    display: flex;
    gap: 12px;
    margin-top: 28px;
}

.form-actions .btn { width: auto; padding: 11px 32px; }

/* Empty state */
.empty-state {
    text-align: center;
    padding: 80px 24px;
}

.empty-state .empty-icon {
    font-size: 56px;
    margin-bottom: 16px;
}

.empty-state h3 {
    font-size: 20px;
    color: var(--text);
    margin-bottom: 8px;
    font-weight: 700;
}

.empty-state p {
    color: var(--text-light);
    margin-bottom: 24px;
}

/* Toast */
.toast {
    position: fixed;
    top: 80px;
    left: 50%;
    transform: translateX(-50%) translateY(-16px);
    padding: 12px 28px;
    border-radius: var(--radius-sm);
    font-size: 14px;
    font-weight: 600;
    opacity: 0;
    transition: all 0.35s cubic-bezier(0.34, 1.56, 0.64, 1);
    z-index: 1000;
    pointer-events: none;
    box-shadow: var(--shadow-lg);
}

.toast.show {
    opacity: 1;
    transform: translateX(-50%) translateY(0);
}

.toast.success { background: var(--success); color: white; box-shadow: 0 4px 16px rgba(16,185,129,0.3); }
.toast.error { background: var(--danger); color: white; box-shadow: 0 4px 16px rgba(239,68,68,0.3); }

/* === Register: Step Indicator === */
.step-indicator {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 0;
    margin-bottom: 32px;
}

.step-dot {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 8px;
    position: relative;
    z-index: 1;
}

.step-dot .step-num {
    width: 36px;
    height: 36px;
    border-radius: var(--radius-full);
    background: var(--bg-subtle);
    color: var(--text-lighter);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 14px;
    font-weight: 700;
    transition: var(--transition-spring);
}

.step-dot .step-label {
    font-size: 12px;
    color: var(--text-lighter);
    font-weight: 500;
    white-space: nowrap;
    transition: var(--transition);
}

.step-dot.active .step-num {
    background: var(--gradient-primary);
    color: white;
    box-shadow: 0 0 0 5px rgba(99,102,241,0.12), 0 2px 8px rgba(99,102,241,0.25);
}

.step-dot.active .step-label {
    color: var(--primary);
    font-weight: 600;
}

.step-dot.done .step-num {
    background: var(--success);
    color: white;
    box-shadow: 0 2px 6px rgba(16,185,129,0.25);
}

.step-dot.done .step-num::after { content: '\2713'; }
.step-dot.done .step-num { font-size: 0; }
.step-dot.done .step-num::after { font-size: 16px; }

.step-dot.done .step-label { color: var(--success); }

.step-line {
    flex: 1;
    height: 2px;
    background: var(--border);
    margin: 0 14px;
    margin-bottom: 22px;
    max-width: 80px;
    transition: var(--transition-slow);
    border-radius: var(--radius-full);
}

.step-line.active {
    background: var(--gradient-primary);
}

/* === Form Steps === */
.form-step {
    display: none;
    animation: stepFadeIn 0.35s ease;
}

.form-step.active {
    display: block;
}

@keyframes stepFadeIn {
    from { opacity: 0; transform: translateY(8px); }
    to { opacity: 1; transform: translateY(0); }
}

/* === Email Display === */
.email-display {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 12px 16px;
    background: var(--bg-subtle);
    border: 1px solid var(--border);
    border-radius: var(--radius-sm);
    font-size: 14px;
    color: var(--text);
}

.email-display .change-email {
    color: var(--primary);
    font-size: 13px;
    font-weight: 600;
    cursor: pointer;
}

.email-display .change-email:hover { text-decoration: underline; }

/* === Code Input Group === */
.code-input-group {
    display: flex;
    gap: 10px;
}

.code-input-group input {
    flex: 1;
    padding: 12px 16px;
    border: 1.5px solid var(--border);
    border-radius: var(--radius-sm);
    font-size: 18px;
    letter-spacing: 6px;
    text-align: center;
    font-weight: 700;
    transition: var(--transition);
    background: var(--card-bg);
    color: var(--text);
}

.code-input-group input:focus {
    outline: none;
    border-color: var(--primary);
    box-shadow: 0 0 0 3px rgba(99,102,241,0.1);
}

.btn-resend {
    padding: 12px 20px;
    border-radius: var(--radius-sm);
    font-size: 13px;
    font-weight: 600;
    white-space: nowrap;
    transition: var(--transition);
    background: var(--bg-subtle);
    color: var(--text-light);
    border: 1px solid var(--border);
    cursor: pointer;
}

.btn-resend:not(:disabled) {
    background: rgba(99,102,241,0.06);
    color: var(--primary);
    border-color: transparent;
}

.btn-resend:not(:disabled):hover {
    background: rgba(99,102,241,0.12);
}

.btn-resend:disabled {
    opacity: 0.5;
    cursor: not-allowed;
}

/* === Scrollbar === */
::-webkit-scrollbar { width: 6px; height: 6px; }
::-webkit-scrollbar-track { background: transparent; }
::-webkit-scrollbar-thumb {
    background: var(--text-faint);
    border-radius: var(--radius-full);
}
::-webkit-scrollbar-thumb:hover { background: var(--text-lighter); }

/* === Responsive for Step Indicator === */
@media (max-width: 480px) {
    .step-indicator { flex-wrap: nowrap; }
    .step-dot .step-label { font-size: 11px; }
    .step-line { max-width: 40px; margin: 0 6px; margin-bottom: 22px; }
    .code-input-group { flex-direction: column; }
    .btn-resend { width: 100%; text-align: center; }
}

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

.fade-in { animation: fadeIn 0.4s ease; }

/* === Responsive === */
@media (max-width: 768px) {
    .container { padding: 0 16px; }
    .hero { padding: 48px 16px 32px; }
    .hero h1 { font-size: 30px; }
    .hero p { font-size: 15px; }
    .subject-grid { grid-template-columns: 1fr; }
    .admin-layout { flex-direction: column; }
    .admin-sidebar {
        width: 100%;
        display: flex;
        overflow-x: auto;
        padding: 12px 0;
        border-right: none;
        border-bottom: 1px solid var(--border-light);
    }
    .admin-sidebar a {
        border-left: none;
        border-bottom: 3px solid transparent;
        padding: 10px 16px;
        white-space: nowrap;
    }
    .admin-sidebar a.active {
        border-left: none;
        border-bottom-color: var(--primary);
    }
    .admin-content { padding: 20px; }
    .question-card { padding: 24px; }
    .quiz-actions { flex-direction: column; }
    .mark-buttons { width: 100%; justify-content: center; }
    .auth-card { padding: 32px 24px; }

    .quiz-result .score { font-size: 44px; }
}

@media (max-width: 480px) {
    .hero h1 { font-size: 26px; }
    .btn-next { width: 100%; justify-content: center; }
    .quiz-result-actions { flex-direction: column; }
    .quiz-result-actions .btn { width: 100%; }
}