/* ============================================
   英语单词记忆 - 样式表
   ============================================ */

/* ─── 基础重置 ─────────────────────────────── */
*, *::before, *::after {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

:root {
    --primary: #4F46E5;
    --primary-hover: #4338CA;
    --primary-light: #EEF2FF;
    --success: #059669;
    --success-light: #ECFDF5;
    --danger: #DC2626;
    --danger-light: #FEF2F2;
    --warning: #D97706;
    --warning-light: #FFFBEB;
    --gray-50: #F9FAFB;
    --gray-100: #F3F4F6;
    --gray-200: #E5E7EB;
    --gray-300: #D1D5DB;
    --gray-400: #9CA3AF;
    --gray-500: #6B7280;
    --gray-600: #4B5563;
    --gray-700: #374151;
    --gray-800: #1F2937;
    --gray-900: #111827;
    --radius: 8px;
    --shadow: 0 1px 3px rgba(0,0,0,0.1), 0 1px 2px rgba(0,0,0,0.06);
    --shadow-md: 0 4px 6px rgba(0,0,0,0.07), 0 2px 4px rgba(0,0,0,0.06);
    --shadow-lg: 0 10px 15px rgba(0,0,0,0.1), 0 4px 6px rgba(0,0,0,0.05);
}

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, "Noto Sans SC", sans-serif;
    font-size: 16px;
    line-height: 1.6;
    color: var(--gray-800);
    background: var(--gray-50);
    min-height: 100vh;
    display: flex;
    flex-direction: column;
    /* 移动端优化：去除点击高亮、禁止横屏自动放大字体 */
    -webkit-tap-highlight-color: transparent;
    -webkit-text-size-adjust: 100%;
    text-size-adjust: 100%;
}

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

.container {
    max-width: 1100px;
    margin: 0 auto;
    padding: 0 20px;
}

/* ─── 导航栏 ────────────────────────────────── */
.navbar {
    background: #fff;
    border-bottom: 1px solid var(--gray-200);
    padding: 0;
    padding-left: env(safe-area-inset-left);
    padding-right: env(safe-area-inset-right);
    position: sticky;
    top: 0;
    z-index: 100;
    box-shadow: var(--shadow);
}

.navbar .container {
    display: flex;
    align-items: center;
    justify-content: space-between;
    height: 56px;
}

.navbar-brand {
    font-size: 18px;
    font-weight: 700;
    color: var(--gray-900);
}

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

.nav-link {
    padding: 8px 12px;
    border-radius: var(--radius);
    color: var(--gray-600);
    font-size: 14px;
    transition: all 0.15s;
}

.nav-link:hover {
    background: var(--gray-100);
    color: var(--gray-900);
}

/* 退出按钮：外观与导航链接保持一致 */
.nav-link-btn {
    background: none;
    border: none;
    cursor: pointer;
    font-family: inherit;
}

.nav-admin {
    color: var(--primary);
    font-weight: 500;
}

.nav-user {
    padding: 8px 12px;
    font-size: 14px;
    color: var(--gray-500);
}

/* ─── 移动端汉堡菜单按钮 ────────────────────── */
/* 桌面端隐藏，≤768px 断点中显示 */
.nav-toggle {
    display: none;
    flex-direction: column;
    justify-content: center;
    gap: 5px;
    width: 44px;
    height: 44px;
    padding: 10px;
    background: none;
    border: none;
    cursor: pointer;
    border-radius: var(--radius);
}

.nav-toggle span {
    display: block;
    width: 100%;
    height: 2px;
    background: var(--gray-700);
    border-radius: 1px;
    transition: transform 0.2s, opacity 0.2s;
}

/* 展开时三线变 X */
.nav-toggle.open span:nth-child(1) { transform: translateY(7px) rotate(45deg); }
.nav-toggle.open span:nth-child(2) { opacity: 0; }
.nav-toggle.open span:nth-child(3) { transform: translateY(-7px) rotate(-45deg); }

/* ─── 按钮 ──────────────────────────────────── */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: 10px 20px;
    border: 1px solid transparent;
    border-radius: var(--radius);
    font-size: 14px;
    font-weight: 500;
    cursor: pointer;
    transition: all 0.15s;
    text-decoration: none;
    line-height: 1.4;
}

.btn:hover { text-decoration: none; }

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

.btn-secondary {
    background: #fff;
    color: var(--gray-700);
    border-color: var(--gray-300);
}
.btn-secondary:hover { background: var(--gray-50); color: var(--gray-900); }

.btn-success {
    background: var(--success);
    color: #fff;
}
.btn-success:hover { background: #047857; color: #fff; }

.btn-danger {
    background: var(--danger);
    color: #fff;
}
.btn-danger:hover { background: #B91C1C; color: #fff; }

.btn-block { width: 100%; }
.btn-lg { padding: 14px 32px; font-size: 16px; }
.btn-sm { padding: 6px 12px; font-size: 13px; }

/* ─── 警告提示 ──────────────────────────────── */
.alert {
    padding: 12px 16px;
    border-radius: var(--radius);
    margin-bottom: 16px;
    font-size: 14px;
}

.alert-error {
    background: var(--danger-light);
    color: var(--danger);
    border: 1px solid #FECACA;
}

.alert-success {
    background: var(--success-light);
    color: var(--success);
    border: 1px solid #A7F3D0;
}

/* ─── 表单 ──────────────────────────────────── */
.form-group {
    margin-bottom: 16px;
}

.form-group label {
    display: block;
    margin-bottom: 6px;
    font-size: 14px;
    font-weight: 500;
    color: var(--gray-700);
}

.form-group input,
.form-group select {
    width: 100%;
    padding: 10px 12px;
    border: 1px solid var(--gray-300);
    border-radius: var(--radius);
    font-size: 14px;
    transition: border-color 0.15s;
    background: #fff;
}

.form-group input:focus,
.form-group select:focus {
    outline: none;
    border-color: var(--primary);
    box-shadow: 0 0 0 3px rgba(79, 70, 229, 0.1);
}

.form-row {
    display: flex;
    gap: 16px;
}

.form-row .form-group { flex: 1; }
.form-group-sm { max-width: 160px; }

/* ─── 首页 Hero ─────────────────────────────── */
.hero {
    text-align: center;
    padding: 60px 20px 40px;
}

.hero h1 {
    font-size: 42px;
    font-weight: 800;
    color: var(--gray-900);
    margin-bottom: 12px;
}

.hero-subtitle {
    font-size: 18px;
    color: var(--gray-500);
    margin-bottom: 40px;
}

.hero-features {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 24px;
    max-width: 800px;
    margin: 0 auto 40px;
}

.feature-card {
    background: #fff;
    padding: 30px 20px;
    border-radius: var(--radius);
    box-shadow: var(--shadow);
    transition: transform 0.2s, box-shadow 0.2s;
}

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

.feature-icon { font-size: 36px; margin-bottom: 12px; }

.feature-card h3 {
    font-size: 16px;
    color: var(--gray-800);
    margin-bottom: 6px;
}

.feature-card p {
    font-size: 13px;
    color: var(--gray-500);
}

.hero-actions {
    display: flex;
    gap: 12px;
    justify-content: center;
    margin-bottom: 24px;
}

.hero-word-count {
    font-size: 14px;
    color: var(--gray-400);
}

.hero-word-count strong {
    color: var(--primary);
}

/* ─── 认证页面 ──────────────────────────────── */
.auth-container {
    max-width: 420px;
    margin: 40px auto;
}

.auth-card {
    background: #fff;
    padding: 32px;
    border-radius: var(--radius);
    box-shadow: var(--shadow-md);
}

.auth-card h2 {
    font-size: 24px;
    text-align: center;
    margin-bottom: 24px;
    color: var(--gray-900);
}

.auth-desc {
    text-align: center;
    color: var(--gray-500);
    font-size: 14px;
    margin-bottom: 20px;
}

.auth-links {
    text-align: center;
    margin-top: 20px;
    font-size: 14px;
    color: var(--gray-500);
}

.auth-sep { margin: 0 8px; color: var(--gray-300); }

/* ─── 仪表盘 ────────────────────────────────── */
.dashboard { padding: 30px 0; }

.dashboard h1 {
    font-size: 28px;
    margin-bottom: 24px;
}

.stats-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
    gap: 16px;
    margin-bottom: 24px;
}

.stat-card {
    background: #fff;
    padding: 20px;
    border-radius: var(--radius);
    box-shadow: var(--shadow);
    text-align: center;
}

.stat-value {
    font-size: 32px;
    font-weight: 700;
    color: var(--gray-900);
}

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

.stat-new .stat-value { color: var(--primary); }
.stat-learning .stat-value { color: var(--warning); }
.stat-review .stat-value { color: #7C3AED; }
.stat-mastered .stat-value { color: var(--success); }
.stat-due .stat-value { color: var(--danger); }

.progress-bar-container {
    background: #fff;
    padding: 16px 20px;
    border-radius: var(--radius);
    box-shadow: var(--shadow);
    margin-bottom: 24px;
}

.progress-label {
    font-size: 14px;
    color: var(--gray-600);
    margin-bottom: 8px;
}

.progress-type-hint {
    color: var(--gray-400);
    font-size: 13px;
}

.progress-bar {
    height: 10px;
    background: var(--gray-200);
    border-radius: 5px;
    overflow: hidden;
}

.progress-fill {
    height: 100%;
    background: linear-gradient(90deg, var(--primary), #7C3AED);
    border-radius: 5px;
    transition: width 0.5s ease;
}

.today-stats {
    background: #fff;
    padding: 16px 20px;
    border-radius: var(--radius);
    box-shadow: var(--shadow);
    margin-bottom: 24px;
}

.today-stats h3 { font-size: 16px; margin-bottom: 12px; }

.today-grid {
    display: flex;
    gap: 32px;
}

.today-item {
    display: flex;
    flex-direction: column;
    align-items: center;
}

.today-value { font-size: 24px; font-weight: 700; }
.today-label { font-size: 13px; color: var(--gray-500); }
.today-correct .today-value { color: var(--success); }
.today-wrong .today-value { color: var(--danger); }

.learn-modes { margin-top: 30px; }

.learn-modes h2 {
    font-size: 20px;
    margin-bottom: 16px;
}

.mode-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 16px;
}

.mode-card {
    background: #fff;
    padding: 30px 20px;
    border-radius: var(--radius);
    box-shadow: var(--shadow);
    text-align: center;
    text-decoration: none;
    color: inherit;
    transition: transform 0.2s, box-shadow 0.2s;
    border: 2px solid transparent;
}

.mode-card:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
    border-color: var(--primary);
    color: inherit;
}

.mode-icon { font-size: 40px; margin-bottom: 12px; }

.mode-card h3 {
    font-size: 18px;
    margin-bottom: 8px;
    color: var(--gray-800);
}

.mode-card p {
    font-size: 13px;
    color: var(--gray-500);
}

/* ─── 学习页面通用 ──────────────────────────── */
.learn-container {
    padding: 30px 0;
    max-width: 700px;
    margin: 0 auto;
}

.learn-container h1 {
    font-size: 28px;
    margin-bottom: 8px;
}

.learn-desc {
    color: var(--gray-500);
    margin-bottom: 24px;
}

/* ─── 类型筛选（单词 / 词组）─────────────────── */
.filter-nav {
    margin-bottom: 12px;
}

.filter-label {
    font-size: 13px;
    color: var(--gray-500);
    align-self: center;
    margin-right: 2px;
}

/* ─── 字母导航 ──────────────────────────────── */
.letter-nav {
    display: flex;
    flex-wrap: wrap;
    gap: 6px;
    margin-bottom: 24px;
}

.letter-btn {
    padding: 6px 12px;
    border: 1px solid var(--gray-300);
    border-radius: var(--radius);
    background: #fff;
    font-size: 13px;
    cursor: pointer;
    transition: all 0.15s;
    color: var(--gray-600);
    text-decoration: none;
}

.letter-btn:hover {
    border-color: var(--primary);
    color: var(--primary);
}

.letter-btn.active {
    background: var(--primary);
    color: #fff;
    border-color: var(--primary);
}

/* ─── 闪卡 ──────────────────────────────────── */
.flashcard-container {
    perspective: 1000px;
    margin-bottom: 20px;
}

.flashcard {
    width: 100%;
    min-height: 280px;
    cursor: pointer;
    position: relative;
}

.flashcard-inner {
    position: relative;
    width: 100%;
    height: 100%;
    transition: transform 0.5s;
    transform-style: preserve-3d;
}

.flashcard.flipped .flashcard-inner {
    transform: rotateY(180deg);
}

.flashcard-front,
.flashcard-back {
    position: absolute;
    width: 100%;
    min-height: 280px;
    backface-visibility: hidden;
    background: #fff;
    border-radius: var(--radius);
    box-shadow: var(--shadow-md);
    padding: 40px;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
}

.flashcard-back {
    transform: rotateY(180deg);
}

.flashcard-word {
    font-size: 42px;
    font-weight: 700;
    color: var(--gray-900);
    margin-bottom: 8px;
    /* 超长单词允许在任意字符处换行 */
    overflow-wrap: anywhere;
    word-break: break-word;
}

.flashcard-phonetic {
    font-size: 16px;
    color: var(--gray-500);
    margin-bottom: 4px;
}

.flashcard-pos {
    font-size: 14px;
    color: var(--primary);
    margin-bottom: 16px;
}

.flashcard-hint {
    font-size: 13px;
    color: var(--gray-400);
}

.flashcard-meaning {
    font-size: 24px;
    font-weight: 600;
    color: var(--gray-800);
    margin-bottom: 12px;
    text-align: center;
    overflow-wrap: anywhere;
    word-break: break-word;
}

.flashcard-example {
    font-size: 14px;
    color: var(--gray-500);
    margin-bottom: 20px;
    text-align: center;
    font-style: italic;
}

.flashcard-actions {
    display: flex;
    gap: 12px;
}

.flashcard-nav {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 16px;
    margin-bottom: 16px;
}

.flashcard-counter {
    font-size: 14px;
    color: var(--gray-500);
}

.flashcard-pagination {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 12px;
    font-size: 14px;
    color: var(--gray-500);
}

/* ─── 间隔重复 ──────────────────────────────── */
.sr-container {
    margin-bottom: 20px;
}

.sr-card {
    background: #fff;
    border-radius: var(--radius);
    box-shadow: var(--shadow-md);
    padding: 40px;
    cursor: pointer;
    min-height: 300px;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
}

.sr-word {
    font-size: 42px;
    font-weight: 700;
    color: var(--gray-900);
    margin-bottom: 8px;
    overflow-wrap: anywhere;
    word-break: break-word;
}

.sr-phonetic {
    font-size: 16px;
    color: var(--gray-500);
    margin-bottom: 4px;
}

.sr-pos {
    font-size: 14px;
    color: var(--primary);
    margin-bottom: 16px;
}

.sr-hint {
    font-size: 13px;
    color: var(--gray-400);
}

.sr-meaning {
    font-size: 24px;
    font-weight: 600;
    color: var(--gray-800);
    margin-bottom: 8px;
    text-align: center;
    overflow-wrap: anywhere;
    word-break: break-word;
}

.sr-example {
    font-size: 14px;
    color: var(--gray-500);
    margin-bottom: 8px;
    text-align: center;
    font-style: italic;
}

.sr-info {
    font-size: 13px;
    color: var(--gray-400);
    margin-bottom: 20px;
}

.sr-actions {
    display: flex;
    gap: 8px;
    flex-wrap: wrap;
    justify-content: center;
}

.btn-rate {
    padding: 10px 16px;
    border: 1px solid var(--gray-300);
    border-radius: var(--radius);
    background: #fff;
    font-size: 14px;
    cursor: pointer;
    transition: all 0.15s;
}

.rate-again:hover { background: var(--danger-light); border-color: var(--danger); color: var(--danger); }
.rate-hard:hover { background: var(--warning-light); border-color: var(--warning); color: var(--warning); }
.rate-good:hover { background: var(--primary-light); border-color: var(--primary); color: var(--primary); }
.rate-easy:hover { background: var(--success-light); border-color: var(--success); color: var(--success); }

.sr-progress {
    text-align: center;
}

.sr-counter {
    font-size: 14px;
    color: var(--gray-500);
}

.sr-done {
    padding: 40px;
}

.sr-done h2 { font-size: 28px; margin-bottom: 12px; }
.sr-done p { color: var(--gray-500); margin-bottom: 24px; }
.sr-done .btn { margin: 0 6px; }

/* ─── 测验 ──────────────────────────────────── */
.quiz-card {
    background: #fff;
    border-radius: var(--radius);
    box-shadow: var(--shadow-md);
    padding: 40px;
    text-align: center;
}

.quiz-word {
    font-size: 42px;
    font-weight: 700;
    color: var(--gray-900);
    margin-bottom: 4px;
    overflow-wrap: anywhere;
    word-break: break-word;
}

.quiz-phonetic {
    font-size: 16px;
    color: var(--gray-500);
    margin-bottom: 24px;
}

.quiz-options {
    display: grid;
    gap: 10px;
}

.quiz-option {
    padding: 14px 20px;
    border: 2px solid var(--gray-200);
    border-radius: var(--radius);
    background: #fff;
    font-size: 16px;
    cursor: pointer;
    transition: all 0.15s;
    text-align: left;
}

.quiz-option:hover:not(:disabled) {
    border-color: var(--primary);
    background: var(--primary-light);
}

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

.quiz-option.wrong {
    border-color: var(--danger);
    background: var(--danger-light);
    color: var(--danger);
}

.quiz-progress {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-top: 16px;
    font-size: 14px;
    color: var(--gray-500);
}

.quiz-score {
    font-weight: 600;
    color: var(--primary);
}

.quiz-result {
    text-align: center;
    padding: 40px;
}

.quiz-result h2 { font-size: 28px; margin-bottom: 16px; }

.result-score {
    font-size: 48px;
    font-weight: 700;
    color: var(--primary);
    margin-bottom: 12px;
}

.result-detail { color: var(--gray-500); margin-bottom: 24px; }

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

/* ─── 统计页面 ──────────────────────────────── */
.chart-container {
    background: #fff;
    padding: 24px;
    border-radius: var(--radius);
    box-shadow: var(--shadow);
    margin-top: 24px;
}

.chart-container h3 {
    font-size: 16px;
    margin-bottom: 20px;
}

.chart-bars {
    display: flex;
    align-items: flex-end;
    gap: 16px;
    height: 140px;
    padding-top: 10px;
}

.chart-bar-item {
    flex: 1;
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 4px;
}

.chart-bar-stack {
    display: flex;
    flex-direction: column;
    justify-content: flex-end;
    width: 100%;
    max-width: 40px;
    height: 100px;
}

.chart-bar {
    width: 100%;
    border-radius: 3px 3px 0 0;
    transition: height 0.3s;
}

.chart-bar-correct { background: var(--success); }
.chart-bar-wrong { background: var(--danger); }

.chart-bar-label {
    font-size: 11px;
    color: var(--gray-500);
}

.chart-bar-value {
    font-size: 12px;
    font-weight: 600;
    color: var(--gray-700);
}

/* ─── 后台管理 ──────────────────────────────── */
.admin-container {
    padding: 30px 0;
}

.admin-container h1 {
    font-size: 28px;
    margin-bottom: 20px;
}

.admin-nav {
    display: flex;
    gap: 4px;
    margin-bottom: 24px;
    border-bottom: 2px solid var(--gray-200);
    padding-bottom: 0;
}

.admin-nav-item {
    padding: 10px 20px;
    font-size: 14px;
    color: var(--gray-500);
    border-bottom: 2px solid transparent;
    margin-bottom: -2px;
    transition: all 0.15s;
    text-decoration: none;
}

.admin-nav-item:hover {
    color: var(--gray-700);
}

.admin-nav-item.active {
    color: var(--primary);
    border-bottom-color: var(--primary);
    font-weight: 500;
}

.admin-card {
    background: #fff;
    padding: 24px;
    border-radius: var(--radius);
    box-shadow: var(--shadow);
    margin-bottom: 20px;
}

.admin-card h2 {
    font-size: 18px;
    margin-bottom: 20px;
    color: var(--gray-800);
}

.admin-form {
    max-width: 700px;
}

/* ─── 表格 ──────────────────────────────────── */
.table-container {
    overflow-x: auto;
    -webkit-overflow-scrolling: touch;
}

.table {
    width: 100%;
    border-collapse: collapse;
    font-size: 14px;
}

.table th {
    text-align: left;
    padding: 10px 12px;
    background: var(--gray-50);
    border-bottom: 2px solid var(--gray-200);
    font-weight: 600;
    color: var(--gray-600);
    white-space: nowrap;
}

.table td {
    padding: 10px 12px;
    border-bottom: 1px solid var(--gray-100);
    color: var(--gray-700);
}

.table tr:hover td {
    background: var(--gray-50);
}

.text-sm { font-size: 12px; color: var(--gray-500); }
.text-center { text-align: center; }
.text-muted { color: var(--gray-500); }

/* ─── 徽章 ──────────────────────────────────── */
.badge {
    display: inline-block;
    padding: 2px 8px;
    border-radius: 10px;
    font-size: 12px;
    font-weight: 500;
}

.badge-admin { background: var(--primary-light); color: var(--primary); }
.badge-user { background: var(--gray-100); color: var(--gray-600); }
.badge-success { background: var(--success-light); color: var(--success); }
.badge-warning { background: var(--warning-light); color: var(--warning); }

/* ─── 分页 ──────────────────────────────────── */
.pagination {
    display: flex;
    gap: 4px;
    margin-top: 16px;
    justify-content: center;
}

.page-btn {
    padding: 6px 12px;
    border: 1px solid var(--gray-300);
    border-radius: var(--radius);
    font-size: 13px;
    color: var(--gray-600);
    text-decoration: none;
    transition: all 0.15s;
}

.page-btn:hover { border-color: var(--primary); color: var(--primary); }
.page-btn.active { background: var(--primary); color: #fff; border-color: var(--primary); }

/* ─── 页脚 ──────────────────────────────────── */
.footer {
    margin-top: auto;
    padding: 20px 0;
    /* 兼容 iPhone 底部安全区域（Home 条） */
    padding-bottom: calc(20px + env(safe-area-inset-bottom));
    padding-left: calc(0px + env(safe-area-inset-left));
    padding-right: calc(0px + env(safe-area-inset-right));
    text-align: center;
    font-size: 13px;
    color: var(--gray-400);
    border-top: 1px solid var(--gray-200);
}

/* ─── 错误页面 ──────────────────────────────── */
.error-container {
    text-align: center;
    padding: 80px 20px;
}

.error-container h1 {
    font-size: 72px;
    font-weight: 800;
    color: var(--gray-300);
    margin-bottom: 12px;
}

.error-container p {
    font-size: 18px;
    color: var(--gray-500);
    margin-bottom: 24px;
}

/* ─── 响应式 ────────────────────────────────── */

/* ── 平板（≤1024px）：侧边栏下移，主内容占满 ── */
@media (max-width: 1024px) {
    .main-wrapper {
        flex-direction: column;
    }

    .sidebar {
        width: 100%;
        padding: 0 20px 24px;
    }

    .sidebar-card {
        position: static;
        max-width: 420px;
        margin: 0 auto;
    }
}

/* ── 手机（≤768px）：汉堡菜单 + 紧凑布局 ── */
@media (max-width: 768px) {
    /* 导航：汉堡菜单 */
    .nav-toggle {
        display: flex;
    }

    .navbar-nav {
        position: absolute;
        top: 100%;
        left: 0;
        right: 0;
        flex-direction: column;
        align-items: stretch;
        gap: 2px;
        background: #fff;
        border-bottom: 1px solid var(--gray-200);
        box-shadow: var(--shadow-md);
        padding: 8px 16px calc(12px + env(safe-area-inset-bottom));
        display: none;
        max-height: calc(100vh - 56px);
        overflow-y: auto;
    }

    .navbar-nav.open {
        display: flex;
    }

    /* 触摸目标 ≥44px（Apple HIG / Material 无障碍建议） */
    .nav-link {
        display: flex;
        align-items: center;
        padding: 12px 10px;
        font-size: 15px;
        min-height: 44px;
    }

    .navbar-nav form {
        display: block;
    }

    .nav-link-btn {
        width: 100%;
        text-align: left;
        min-height: 44px;
    }

    /* 首页 Hero */
    .hero {
        padding: 36px 16px 28px;
    }

    .hero h1 { font-size: 28px; }
    .hero-subtitle { font-size: 15px; margin-bottom: 28px; }

    .hero-features {
        grid-template-columns: 1fr;
        gap: 14px;
    }

    .hero-actions {
        flex-direction: column;
        gap: 10px;
    }

    .hero-actions .btn {
        width: 100%;
        min-height: 48px;
    }

    /* 仪表盘与统计 */
    .dashboard, .learn-container { padding: 20px 0; }
    .dashboard h1, .learn-container h1 { font-size: 24px; }

    .stats-grid {
        grid-template-columns: repeat(2, 1fr);
        gap: 12px;
    }

    .dashboard-header {
        flex-direction: column;
        align-items: stretch;
    }

    .book-form {
        width: 100%;
    }

    .book-form select {
        min-width: 0;
        flex: 1;
        min-height: 44px;
    }

    .today-grid {
        gap: 16px;
        justify-content: space-around;
    }

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

    /* 表单 */
    .form-row {
        flex-direction: column;
        gap: 0;
    }

    .form-group-sm {
        max-width: 100%;
    }

    .form-group input,
    .form-group select {
        min-height: 44px;
        font-size: 16px; /* 防止 iOS 聚焦输入框时自动缩放页面 */
    }

    .auth-container {
        margin: 20px auto;
    }

    .auth-card {
        padding: 24px 20px;
    }

    /* 字母导航：横向滑动，避免 27 个按钮折行占满首屏 */
    .letter-nav {
        flex-wrap: nowrap;
        overflow-x: auto;
        -webkit-overflow-scrolling: touch;
        padding-bottom: 8px;
        margin-bottom: 20px;
    }

    .letter-btn {
        flex-shrink: 0;
        min-width: 40px;
        min-height: 40px;
    }

    /* 学习卡片紧凑化 */
    .flashcard-word, .sr-word, .quiz-word { font-size: 30px; }
    .flashcard-front, .flashcard-back { padding: 24px 18px; min-height: 220px; }
    .flashcard-meaning, .sr-meaning { font-size: 20px; }

    .flashcard-actions {
        width: 100%;
        flex-direction: column;
        gap: 10px;
    }

    .flashcard-actions .btn {
        width: 100%;
        min-height: 48px;
    }

    .sr-card { padding: 24px 18px; min-height: 240px; }

    /* 间隔重复评分按钮：2×2 网格全宽 */
    .sr-actions {
        display: grid;
        grid-template-columns: repeat(2, 1fr);
        width: 100%;
        gap: 10px;
    }

    .btn-rate {
        width: 100%;
        min-height: 48px;
    }

    .quiz-card { padding: 24px 18px; }

    .quiz-option {
        min-height: 48px;
        padding: 12px 16px;
        font-size: 15px;
    }

    .flashcard-nav, .flashcard-pagination {
        flex-wrap: wrap;
    }

    .flashcard-nav .btn,
    .flashcard-pagination .btn {
        min-height: 44px;
    }

    .sr-done, .quiz-result { padding: 24px 16px; }
    .sr-done .btn, .result-actions .btn { margin: 4px 0; min-height: 44px; }
    .result-actions { flex-direction: column; }

    /* 图表 */
    .chart-bars { gap: 8px; }

    /* 后台管理：Tab 栏横向滑动 */
    .admin-nav {
        overflow-x: auto;
        -webkit-overflow-scrolling: touch;
        flex-wrap: nowrap;
    }

    .admin-nav-item {
        white-space: nowrap;
        flex-shrink: 0;
    }

    /* 通用按钮触摸目标 */
    .btn { min-height: 44px; }

    /* 分页 */
    .pagination { flex-wrap: wrap; }
    .page-btn { min-width: 40px; min-height: 40px; }

    /* 弹窗 */
    .modal-content { padding: 20px 16px; }
}

/* ── 小屏手机（≤480px）────────────────────── */
@media (max-width: 480px) {
    .container { padding: 0 14px; }

    .hero h1 { font-size: 26px; }

    .flashcard-word, .sr-word, .quiz-word { font-size: 26px; }
    .flashcard-front, .flashcard-back { min-height: 200px; }

    .stat-value { font-size: 26px; }
    .today-value { font-size: 20px; }
    .result-score { font-size: 40px; }

    .flashcard-pagination { gap: 8px; font-size: 13px; }

    .chart-bar-stack { max-width: 32px; }
    .chart-bar-label { font-size: 10px; }
}

/* ── 触屏设备：移除粘滞 hover 态 ──────────────── */
@media (hover: none) {
    .quiz-option:hover:not(:disabled) {
        border-color: var(--gray-200);
        background: #fff;
    }

    .letter-btn:hover {
        border-color: var(--gray-300);
        color: var(--gray-600);
    }

    .letter-btn.active:hover {
        background: var(--primary);
        color: #fff;
        border-color: var(--primary);
    }

    .page-btn:hover {
        border-color: var(--gray-300);
        color: var(--gray-600);
    }

    .btn-rate:hover {
        background: #fff;
        border-color: var(--gray-300);
    }
}

/* ─── 布局：主内容 + 侧边栏 ─────────────────── */
.main-wrapper {
    display: flex;
    gap: 0;
    flex: 1;
}

.main-content {
    flex: 1;
    min-width: 0;
}

.sidebar {
    width: 260px;
    flex-shrink: 0;
    padding: 30px 20px 30px 0;
}

.sidebar-card {
    background: #fff;
    border-radius: var(--radius);
    box-shadow: var(--shadow);
    padding: 24px;
    position: sticky;
    top: 72px;
}

.sidebar-card h3 {
    font-size: 16px;
    color: var(--gray-800);
    margin-bottom: 8px;
    text-align: center;
}

.sidebar-desc {
    font-size: 13px;
    color: var(--gray-500);
    text-align: center;
    margin-bottom: 16px;
}

.qr-placeholder {
    text-align: center;
}

.qr-box {
    width: 180px;
    height: 180px;
    margin: 0 auto;
    border: 2px dashed var(--gray-300);
    border-radius: var(--radius);
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    background: var(--gray-50);
}

.qr-box img {
    width: 100%;
    height: 100%;
    object-fit: contain;
    border-radius: var(--radius);
}

.qr-icon {
    font-size: 32px;
    margin-bottom: 4px;
}

.qr-text {
    font-size: 14px;
    color: var(--gray-500);
    font-weight: 500;
}

.qr-hint {
    font-size: 11px;
    color: var(--gray-400);
    margin-top: 4px;
    text-align: center;
    line-height: 1.4;
}

/* ─── 仪表盘头部 ────────────────────────────── */
.dashboard-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 24px;
    flex-wrap: wrap;
    gap: 12px;
}

.dashboard-header h1 {
    margin-bottom: 0;
}

.book-selector {
    display: flex;
    align-items: center;
}

.book-form {
    display: flex;
    align-items: center;
    gap: 8px;
}

.book-form label {
    font-size: 14px;
    color: var(--gray-600);
    white-space: nowrap;
}

.book-form select {
    padding: 8px 12px;
    border: 1px solid var(--gray-300);
    border-radius: var(--radius);
    font-size: 14px;
    background: #fff;
    cursor: pointer;
    min-width: 160px;
}

.book-form select:focus {
    outline: none;
    border-color: var(--primary);
    box-shadow: 0 0 0 3px rgba(79, 70, 229, 0.1);
}

/* ─── 2列统计卡片 ───────────────────────────── */
.stats-grid-2col {
    grid-template-columns: repeat(2, 1fr) !important;
}

@media (max-width: 480px) {
    .stats-grid-2col {
        grid-template-columns: repeat(2, 1fr) !important;
    }
}

/* ─── 弹窗 ──────────────────────────────────── */
.modal {
    position: fixed;
    inset: 0;
    z-index: 1000;
    display: flex;
    align-items: center;
    justify-content: center;
}

.modal-overlay {
    position: absolute;
    inset: 0;
    background: rgba(0,0,0,0.4);
}

.modal-content {
    position: relative;
    background: #fff;
    border-radius: var(--radius);
    padding: 24px;
    width: 90%;
    max-width: 500px;
    box-shadow: var(--shadow-lg);
    max-height: 90vh;
    overflow-y: auto;
}

.modal-content h3 {
    font-size: 18px;
    margin-bottom: 16px;
    color: var(--gray-800);
}

.modal-content .form-group {
    margin-bottom: 12px;
}

.modal-content textarea {
    font-family: inherit;
    font-size: 14px;
    resize: vertical;
}

/* ─── 组织管理员徽章 ─────────────────────────── */
.badge-org {
    background: #F3E8FF;
    color: #7C3AED;
}

/* ─── 单词发音（TTS）────────────────────────── */
.tts-btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 4px;
    padding: 4px 10px;
    min-height: 32px;
    font-size: 14px;
    border: 1px solid var(--gray-300);
    border-radius: 999px;
    background: #fff;
    color: var(--gray-600);
    cursor: pointer;
    vertical-align: middle;
    transition: all 0.15s ease;
}

.tts-btn:hover {
    border-color: var(--primary);
    color: var(--primary);
    background: var(--primary-light, #EEF2FF);
}

.tts-btn-lg {
    padding: 8px 14px;
    font-size: 20px;
}

.flashcard-word-row,
.sr-word-row {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 12px;
    flex-wrap: wrap;
}

/* ─── 试卷作答页 ────────────────────────────── */
.exam-take-card {
    margin-bottom: 14px;
    border: 1px solid var(--gray-200);
    transition: border-color 0.2s ease;
}

.exam-take-card.answered {
    border-color: var(--success, #10B981);
}

.exam-question-stem {
    display: flex;
    align-items: center;
    gap: 8px;
    flex-wrap: wrap;
    font-size: 15px;
    color: var(--gray-700);
    margin-bottom: 10px;
}

.exam-question-stem-text {
    font-size: 18px;
    font-weight: 600;
    color: var(--gray-900);
    line-height: 1.6;
    word-break: break-word;
}

.exam-options {
    margin-top: 10px;
}

.exam-options .quiz-option {
    display: flex;
    align-items: center;
    gap: 8px;
    cursor: pointer;
    user-select: none;
}

.exam-options .quiz-option input[type="radio"] {
    accent-color: var(--primary);
    width: 16px;
    height: 16px;
    cursor: pointer;
}

.exam-options .quiz-option:has(input[type="radio"]:checked) {
    border-color: var(--primary);
    background: var(--primary-light, #EEF2FF);
}

.exam-blank-input {
    width: 100%;
    padding: 10px 14px;
    font-size: 16px;
    border: 1px solid var(--gray-300);
    border-radius: var(--radius);
}

.exam-blank-input:focus {
    outline: none;
    border-color: var(--primary);
    box-shadow: 0 0 0 3px rgba(79, 70, 229, 0.1);
}

.exam-submit-bar {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 12px;
    flex-wrap: wrap;
    margin-top: 20px;
    padding: 16px;
    background: #fff;
    border-radius: var(--radius);
    box-shadow: var(--shadow);
    position: sticky;
    bottom: 12px;
}

/* ─── 试卷题目预览 / 成绩回顾 ───────────────── */
.exam-question-preview {
    padding: 14px 16px;
    border: 1px solid var(--gray-200);
    border-left: 4px solid var(--gray-200);
    border-radius: var(--radius);
    margin-bottom: 10px;
    background: #fff;
}

.exam-question-preview .exam-question-stem {
    margin-bottom: 6px;
    font-size: 16px;
    color: var(--gray-900);
}

.exam-question-preview .exam-question-stem-text {
    font-size: 16px;
}

.exam-q-correct {
    border-left-color: var(--success, #10B981);
}

.exam-q-wrong {
    border-left-color: var(--danger, #EF4444);
}

.exam-question-options {
    list-style: none;
    padding: 0;
    margin: 8px 0 0;
    display: grid;
    gap: 6px;
}

.exam-question-options li {
    padding: 8px 12px;
    border: 1px solid var(--gray-200);
    border-radius: var(--radius);
    font-size: 14px;
    display: flex;
    align-items: center;
    gap: 8px;
    flex-wrap: wrap;
}

.exam-option-correct {
    border-color: var(--success, #10B981) !important;
    background: var(--success-light, #ECFDF5) !important;
}

.exam-option-wrong {
    border-color: var(--danger, #EF4444) !important;
    background: var(--danger-light, #FEF2F2) !important;
}

.exam-question-answer {
    margin: 8px 0 0;
    font-size: 14px;
}

.exam-question-explanation {
    margin: 6px 0 0;
    font-size: 13px;
}

.text-success { color: var(--success, #10B981); }
.text-danger { color: var(--danger, #EF4444); }

@media (max-width: 768px) {
    .exam-question-stem-text { font-size: 16px; }
    .exam-submit-bar { position: static; }
    .tts-btn-lg { font-size: 18px; padding: 6px 12px; }
}