/* ═══════════════════════════════════════
   CSS 变量 & 暗黑模式
   ═══════════════════════════════════════ */
:root {
  --primary: #2563eb;
  --primary-hover: #1d4ed8;
  --primary-dark: #1e40af;
  --primary-light: #bfdbfe;
  --primary-bg: #eff6ff;
  --danger: #dc2626;
  --danger-hover: #b91c1c;
  --success: #16a34a;
  --success-hover: #15803d;
  --warning: #f59e0b;
  --warning-hover: #d97706;
  --bg: #f5f7fa;
  --card-bg: #ffffff;
  --text: #333333;
  --text-secondary: #64748b;
  --text-muted: #94a3b8;
  --border: #e2e8f0;
  --border-light: #f1f5f9;
  --light-bg: #f1f5f9;
  --overlay: rgba(0,0,0,.5);
  --shadow-sm: 0 1px 4px rgba(0,0,0,.04);
  --shadow: 0 2px 8px rgba(0,0,0,.06);
  --shadow-lg: 0 4px 24px rgba(0,0,0,.08);
  --radius: 8px;
  --radius-lg: 12px;
  --radius-xl: 16px;
  --nav-height: 52px;
  --header-height: 50px;
}

body.dark-mode {
  --primary: #60a5fa;
  --primary-hover: #93c5fd;
  --primary-dark: #1e3a5f;
  --primary-light: #3b82f6;
  --primary-bg: #1e293b;
  --bg: #0f172a;
  --card-bg: #1e293b;
  --text: #e2e8f0;
  --text-secondary: #94a3b8;
  --text-muted: #64748b;
  --border: #334155;
  --border-light: #1e293b;
  --light-bg: #1e293b;
  --overlay: rgba(0,0,0,.7);
  --shadow-sm: 0 1px 4px rgba(0,0,0,.2);
  --shadow: 0 2px 8px rgba(0,0,0,.3);
  --shadow-lg: 0 4px 24px rgba(0,0,0,.4);
}

/* ═══════════════════════════════════════
   Base
   ═══════════════════════════════════════ */
*{margin:0;padding:0;box-sizing:border-box}
body{font-family:-apple-system,"Microsoft YaHei","PingFang SC",sans-serif;background:var(--bg);color:var(--text);line-height:1.6}
a{color:var(--primary);text-decoration:none}
a:hover{text-decoration:underline}

/* ═══════════════════════════════════════
   Navbar
   ═══════════════════════════════════════ */
.navbar{background:var(--primary-dark);color:#fff;padding:12px 24px;display:flex;justify-content:space-between;align-items:center;position:sticky;top:0;z-index:100}
.nav-brand{font-size:18px;font-weight:700}
.nav-links{display:flex;gap:16px;align-items:center}
.nav-links a{color:var(--primary-light);font-size:14px;padding:4px 12px;border-radius:6px;transition:.2s}
.nav-links a:hover,.nav-links a.active{color:#fff;background:rgba(255,255,255,.15)}
.nav-logout{color:#fca5a5!important}
.nav-dark-toggle{background:none;border:1px solid rgba(255,255,255,.3);color:#fff;width:32px;height:32px;border-radius:6px;cursor:pointer;font-size:16px;display:flex;align-items:center;justify-content:center;transition:.2s;margin-left:8px}
.nav-dark-toggle:hover{background:rgba(255,255,255,.15)}

.container{max-width:800px;margin:0 auto;padding:24px 16px}
.footer{text-align:center;padding:24px;color:var(--text-muted);font-size:12px}

/* ═══════════════════════════════════════
   Buttons
   ═══════════════════════════════════════ */
.btn{display:inline-block;padding:8px 20px;border:none;border-radius:var(--radius);cursor:pointer;font-size:14px;font-weight:500;transition:.2s;text-align:center}
.btn-primary{background:var(--primary);color:#fff}.btn-primary:hover{background:var(--primary-hover)}
.btn-outline{background:var(--card-bg);color:var(--primary);border:2px solid var(--primary)}.btn-outline:hover{background:var(--primary-bg)}
.btn-danger{background:var(--danger);color:#fff}.btn-danger:hover{background:var(--danger-hover)}
.btn-warning{background:var(--warning);color:#fff}.btn-warning:hover{background:var(--warning-hover)}
.btn-success{background:var(--success);color:#fff}.btn-success:hover{background:var(--success-hover)}
.btn-sm{padding:4px 12px;font-size:12px}
.btn-lg{padding:12px 32px;font-size:16px}
.btn-block{display:block;width:100%}

/* ═══════════════════════════════════════
   Auth
   ═══════════════════════════════════════ */
.auth-card{max-width:400px;margin:60px auto;background:var(--card-bg);padding:40px;border-radius:var(--radius-xl);box-shadow:var(--shadow-lg)}
.auth-card h1{text-align:center;margin-bottom:8px}
.subtitle{text-align:center;color:var(--text-secondary);margin-bottom:24px}
.auth-switch{text-align:center;margin-top:16px;color:var(--text-secondary);font-size:14px}
.form-group{margin-bottom:16px}
.form-group label{display:block;margin-bottom:4px;font-weight:500;font-size:14px}
.form-group input{width:100%;padding:10px 12px;border:2px solid var(--border);border-radius:var(--radius);font-size:15px;transition:.2s;background:var(--card-bg);color:var(--text)}
.form-group input:focus{border-color:var(--primary);outline:none}
.form-row{display:flex;align-items:center;gap:12px}
.input-sm{width:80px;padding:8px;border:2px solid var(--border);border-radius:var(--radius);font-size:15px;text-align:center;background:var(--card-bg);color:var(--text)}

/* ═══════════════════════════════════════
   Dashboard
   ═══════════════════════════════════════ */
.welcome h1{font-size:24px;margin-bottom:4px}
.stats-grid{display:grid;grid-template-columns:repeat(auto-fit,minmax(160px,1fr));gap:16px;margin:24px 0}
.stat-card{background:var(--card-bg);padding:20px;border-radius:var(--radius-lg);text-align:center;box-shadow:var(--shadow)}
.stat-value{font-size:32px;font-weight:700;color:var(--primary)}
.stat-card-warn .stat-value{color:var(--warning)}
.stat-label{font-size:13px;color:var(--text-secondary);margin-top:4px}
.action-bar{display:flex;gap:12px;margin:16px 0;flex-wrap:wrap}

/* ═══════════════════════════════════════
   Tables
   ═══════════════════════════════════════ */
.table-wrap{overflow-x:auto}
.data-table{width:100%;border-collapse:collapse;background:var(--card-bg);border-radius:var(--radius-lg);overflow:hidden;box-shadow:var(--shadow)}
.data-table th,.data-table td{padding:12px 16px;text-align:left;border-bottom:1px solid var(--border-light);font-size:14px}
.data-table th{background:var(--light-bg);font-weight:600;color:var(--text-secondary)}

/* ═══════════════════════════════════════
   Badges
   ═══════════════════════════════════════ */
.badge{display:inline-block;padding:2px 10px;border-radius:20px;font-size:12px;font-weight:600}
.badge-green{background:#dcfce7;color:#166534}
.badge-yellow{background:#fef9c3;color:#854d0e}
.badge-red{background:#fecaca;color:#991b1b}

/* ═══════════════════════════════════════
   Config / Sections
   ═══════════════════════════════════════ */
.config-page h1{margin-bottom:24px}
.section{background:var(--card-bg);padding:24px;border-radius:var(--radius-lg);margin-bottom:20px;box-shadow:var(--shadow)}
.section h2{font-size:16px;margin-bottom:12px}
.hint{color:var(--text-muted);font-size:13px;margin-bottom:8px}
.checkbox-group,.radio-group{display:flex;flex-direction:column;gap:8px}
.checkbox-item,.radio-group label{display:flex;align-items:center;gap:8px;padding:6px 0;cursor:pointer;font-size:14px}
.check-all{padding:8px 0;border-bottom:2px solid var(--border-light);margin-bottom:4px}

/* ═══════════════════════════════════════
   Exam Page — Layout
   ═══════════════════════════════════════ */
.exam-page{display:flex;gap:20px;position:relative;max-width:1100px;margin:0 auto}
.exam-main{flex:1;min-width:0}
.exam-header{position:fixed;top:var(--nav-height);left:0;right:0;background:var(--card-bg);border-bottom:2px solid var(--border);display:flex;justify-content:space-between;align-items:center;padding:10px 24px;z-index:90}
.exam-progress{font-weight:600;font-size:15px}
.exam-timer{font-size:20px;font-weight:700;color:var(--danger);font-variant-numeric:tabular-nums}

.q-card{background:var(--card-bg);margin-top:150px;padding:24px;border-radius:var(--radius-lg);box-shadow:var(--shadow)}
.q-card.hidden{display:none}
.q-header{display:flex;gap:12px;align-items:center;margin-bottom:16px;flex-wrap:wrap}
.q-number{font-weight:700;font-size:15px}
.q-section{font-size:12px;color:var(--text-secondary);background:var(--light-bg);padding:2px 10px;border-radius:20px}
.q-type{font-size:12px;color:#6366f1;background:#eef2ff;padding:2px 10px;border-radius:20px}
.q-text{font-size:16px;font-weight:500;margin-bottom:20px;line-height:1.8}
.q-options{display:flex;flex-direction:column;gap:8px}
.q-option{display:flex;align-items:center;gap:12px;padding:12px 16px;border:2px solid var(--border);border-radius:10px;cursor:pointer;transition:.2s}
.q-option:hover{border-color:#93c5fd;background:var(--primary-bg)}
.q-option:has(input:checked){border-color:var(--primary);background:var(--primary-bg)}
.q-option input[type=radio]{position:absolute;opacity:0;width:0;height:0}
.q-option-letter{display:inline-flex;align-items:center;justify-content:center;min-width:28px;height:28px;background:var(--light-bg);border-radius:6px;font-weight:600;font-size:13px;flex-shrink:0;color:var(--text)}
.q-option:has(input:checked) .q-option-letter{background:var(--primary);color:#fff}
.q-option-text{font-size:14px;line-height:1.6}
.q-footer{display:flex;justify-content:space-between;margin-top:20px;padding-top:16px;border-top:1px solid var(--border-light)}

/* ═══════════════════════════════════════
   Exam Page — Sidebar (答题卡)
   ═══════════════════════════════════════ */
.exam-sidebar{width:220px;flex-shrink:0;margin-top:150px;position:sticky;top:calc(var(--nav-height) + 60px);align-self:flex-start;background:var(--card-bg);border-radius:var(--radius-lg);padding:16px;box-shadow:var(--shadow);max-height:calc(100vh - var(--nav-height) - 80px);overflow-y:auto}
.exam-sidebar h4{font-size:14px;margin-bottom:12px;color:var(--text)}
.exam-sidebar-count{font-size:12px;color:var(--text-secondary);margin-bottom:12px}
.question-grid{display:grid;grid-template-columns:repeat(5,1fr);gap:6px}
.q-grid-btn{width:100%;aspect-ratio:1;border:2px solid var(--border);background:var(--card-bg);border-radius:6px;cursor:pointer;font-size:12px;font-weight:500;transition:.15s;color:var(--text);display:flex;align-items:center;justify-content:center}
.q-grid-btn:hover{border-color:var(--primary)}
.q-grid-btn.active{background:var(--primary);color:#fff;border-color:var(--primary)}
.q-grid-btn.answered{background:#dcfce7;border-color:#86efac;color:#166534}
.q-grid-btn.active.answered{background:var(--primary);color:#fff;border-color:var(--primary)}
body.dark-mode .q-grid-btn.answered{background:#064e3b;border-color:#059669;color:#6ee7b7}
body.dark-mode .q-grid-btn.active.answered{background:var(--primary);color:#fff;border-color:var(--primary)}

/* Mobile sidebar toggle */
.sidebar-toggle-btn{display:none;position:fixed;bottom:20px;right:20px;width:48px;height:48px;border-radius:50%;background:var(--primary);color:#fff;border:none;font-size:20px;cursor:pointer;z-index:95;box-shadow:0 4px 12px rgba(37,99,235,.4);align-items:center;justify-content:center}
.sidebar-overlay{display:none;position:fixed;inset:0;background:rgba(0,0,0,.5);z-index:92}

@media(max-width:900px){
  .exam-sidebar{position:fixed;top:0;right:0;bottom:0;margin-top:0;z-index:93;border-radius:0;width:280px;transform:translateX(100%);transition:transform .3s ease;max-height:100vh}
  .exam-sidebar.open{transform:translateX(0)}
  .sidebar-toggle-btn{display:flex}
  .sidebar-overlay.open{display:block}
  .exam-page{max-width:none}
}

/* ═══════════════════════════════════════
   Modal
   ═══════════════════════════════════════ */
.modal{position:fixed;inset:0;background:var(--overlay);display:flex;align-items:center;justify-content:center;z-index:200}
.modal.hidden{display:none}
.modal-content{background:var(--card-bg);padding:32px;border-radius:var(--radius-xl);max-width:400px;text-align:center}
.modal-content h3{margin-bottom:12px;color:var(--text)}
.modal-content p{color:var(--text-secondary)}
.modal-actions{display:flex;gap:12px;justify-content:center;margin-top:20px}

/* ═══════════════════════════════════════
   Result
   ═══════════════════════════════════════ */
.result-hero{text-align:center;padding:40px 20px;border-radius:var(--radius-xl);margin-bottom:24px;color:#fff}
.result-green{background:linear-gradient(135deg,#16a34a,#22c55e)}
.result-yellow{background:linear-gradient(135deg,#d97706,#f59e0b)}
.result-red{background:linear-gradient(135deg,#dc2626,#ef4444)}
.result-score{font-size:56px;font-weight:800}
.result-accuracy{font-size:20px;margin-top:4px}
.result-time{font-size:14px;margin-top:8px;opacity:.8}
.result-verdict{font-size:22px;margin-top:12px}
.result-actions{display:flex;gap:12px;justify-content:center;margin-bottom:24px}

.review-card{background:var(--card-bg);border-radius:var(--radius-lg);padding:20px;margin-bottom:12px;border-left:4px solid var(--border);box-shadow:var(--shadow-sm)}
.review-correct{border-left-color:var(--success)}
.review-wrong{border-left-color:var(--danger)}
.review-header{display:flex;gap:8px;align-items:center;margin-bottom:8px;flex-wrap:wrap}
.review-options{margin-top:8px}
.q-option-review{display:flex;align-items:center;gap:8px;padding:6px 12px;border-radius:6px;margin-bottom:4px;font-size:14px}
.option-correct{background:#dcfce7}
.option-wrong{background:#fecaca;text-decoration:line-through}
.option-tag{font-size:11px;background:var(--primary);color:#fff;padding:1px 8px;border-radius:10px;margin-left:auto}
.option-tag-wrong{background:var(--danger)}
.review-explanation{background:#fefce8;padding:10px 14px;border-radius:var(--radius);font-size:13px;margin-top:8px;color:#854d0e}

/* ═══════════════════════════════════════
   Wrong answers
   ═══════════════════════════════════════ */
.wrong-header{display:flex;justify-content:space-between;align-items:center;flex-wrap:wrap;gap:12px;margin-bottom:16px}
.wrong-stats{color:var(--text-secondary);font-size:14px}
.wrong-filters{display:flex;gap:8px}
.wrong-card{background:var(--card-bg);border-radius:var(--radius-lg);padding:16px 20px;margin-bottom:12px;border-left:4px solid var(--danger);box-shadow:var(--shadow-sm)}
.wrong-reviewed{border-left-color:var(--success);opacity:.7}
.wrong-card-header{display:flex;gap:8px;align-items:center;margin-bottom:8px;flex-wrap:wrap}
.wrong-answers{margin-top:8px;font-size:14px}
.wrong-your{color:var(--danger);margin-bottom:2px}
.wrong-correct{color:var(--success);margin-bottom:4px}
.wrong-explanation{color:#854d0e;font-size:13px;margin-top:4px}
.wrong-card-footer{display:flex;justify-content:space-between;align-items:center;margin-top:12px;padding-top:8px;border-top:1px solid var(--border-light)}
.wrong-date{color:var(--text-muted);font-size:12px}
.wrong-retake{margin-bottom:16px}
.text-red{color:var(--danger)}.text-green{color:var(--success)}
.empty-state{text-align:center;padding:60px 20px;color:var(--text-muted)}
.empty-state p{font-size:18px;margin-bottom:16px}

/* ═══════════════════════════════════════
   Alerts
   ═══════════════════════════════════════ */
.alert{padding:10px 16px;border-radius:var(--radius);margin-bottom:16px;font-size:14px}
.alert-error{background:#fecaca;color:#991b1b}
.alert-info{background:#dbeafe;color:#1e40af}

.import-form{display:flex;gap:12px;align-items:center;margin-top:12px}
.import-form input[type=file]{flex:1;padding:8px;border:2px solid var(--border);border-radius:var(--radius);background:var(--card-bg);color:var(--text)}

/* ═══════════════════════════════════════
   Responsive
   ═══════════════════════════════════════ */
@media(max-width:600px){
  .stats-grid{grid-template-columns:1fr}
  .navbar{flex-direction:column;gap:8px}
  .exam-page{flex-direction:column}
  .q-card{margin-top:180px;padding:16px}
}

/* ═══════════════════════════════════════
   Knowledge Outline
   ═══════════════════════════════════════ */
.knowledge-page{max-width:900px}
.outline-header{display:flex;justify-content:space-between;align-items:center;flex-wrap:wrap;gap:12px;margin-bottom:20px}
.outline-progress{display:flex;align-items:center;gap:12px;font-size:14px;color:var(--text-secondary)}
.outline-progress-bar{flex:1;min-width:120px;height:8px;background:var(--border);border-radius:4px;overflow:hidden}
.outline-progress-fill{height:100%;background:var(--primary);border-radius:4px;transition:width .3s}
.outline-actions{display:flex;gap:8px}
.outline-tree{list-style:none;padding:0}
.outline-item{margin:0;padding:0}
.outline-item.collapsed>.outline-children{display:none}
.outline-item .outline-children{padding-left:24px;list-style:none}
.outline-row{display:flex;align-items:center;gap:8px;padding:6px 8px;border-radius:var(--radius);cursor:pointer;transition:.15s}
.outline-row:hover{background:var(--light-bg)}
.outline-row.learned .outline-title-link{color:var(--success)}
.outline-toggle{width:20px;height:20px;display:flex;align-items:center;justify-content:center;cursor:pointer;flex-shrink:0;color:var(--text-muted);font-size:12px;user-select:none;border:none;background:none;padding:0}
.outline-toggle:hover{color:var(--text-secondary)}
.toggle-placeholder{width:20px;flex-shrink:0}
.outline-learned-badge{font-size:11px;color:var(--success);background:#dcfce7;padding:1px 8px;border-radius:10px;white-space:nowrap}
.outline-title-link{font-size:14px;color:var(--primary);text-decoration:none;flex:1}
.outline-title-link:hover{text-decoration:underline}
.outline-item.chapter>.outline-row .outline-title-link{font-weight:600;font-size:15px}
.outline-chapter-progress{font-size:12px;color:var(--text-secondary);margin-left:auto;white-space:nowrap}
.outline-key-points{font-size:12px;color:var(--text-secondary);margin-left:12px;max-width:300px;overflow:hidden;text-overflow:ellipsis;white-space:nowrap}

/* ═══════════════════════════════════════
   Knowledge Detail
   ═══════════════════════════════════════ */
.detail-page{max-width:800px}
.detail-back{margin-bottom:16px}
.detail-header{display:flex;justify-content:space-between;align-items:center;flex-wrap:wrap;gap:12px;margin-bottom:16px}
.detail-header h1{font-size:22px;margin:0}
.detail-chapter{font-size:13px;color:var(--text-secondary);margin-bottom:20px}
.detail-section{margin-bottom:24px}
.detail-section h2{font-size:16px;color:var(--primary-dark);border-bottom:2px solid var(--border);padding-bottom:6px;margin-bottom:12px}
body.dark-mode .detail-section h2{color:var(--primary)}
.detail-section ul{padding-left:20px;margin:8px 0}
.detail-section li{margin-bottom:4px;font-size:14px;line-height:1.7}
.detail-benchmark{background:var(--light-bg);border-left:3px solid var(--primary);padding:10px 14px;margin:6px 0;font-size:14px;border-radius:0 6px 6px 0}
.detail-actions{display:flex;gap:12px;flex-wrap:wrap;margin:24px 0}
.detail-learned-badge{display:inline-block;background:#dcfce7;color:var(--success);padding:4px 14px;border-radius:20px;font-size:14px;font-weight:500}

/* ═══════════════════════════════════════
   Question List & Form
   ═══════════════════════════════════════ */
.filter-row{display:flex;gap:12px;align-items:center;flex-wrap:wrap}
.filter-row select,
.filter-row input[type="text"]{padding:8px 12px;border:2px solid var(--border);border-radius:var(--radius);background:var(--card-bg);color:var(--text);font-size:14px}
.filter-row select{min-width:120px}
.filter-row input[type="text"]{flex:1;min-width:200px}
.q-text-cell{max-width:300px;overflow:hidden;text-overflow:ellipsis;white-space:nowrap}
.section-input-group{display:flex;gap:12px;align-items:center}
.section-input-group select{flex:1}
.section-input-group input{flex:1}