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

:root {
  --primary: #4f6cf7;
  --primary-dark: #3a56d4;
  --primary-light: #eef1ff;
  --success: #22c55e;
  --success-light: #dcfce7;
  --danger: #ef4444;
  --danger-light: #fee2e2;
  --warning: #f59e0b;
  --warning-light: #fef3c7;
  --gray-50: #f8fafc;
  --gray-100: #f1f5f9;
  --gray-200: #e2e8f0;
  --gray-300: #cbd5e1;
  --gray-400: #94a3b8;
  --gray-500: #64748b;
  --gray-600: #475569;
  --gray-700: #334155;
  --gray-800: #1e293b;
  --gray-900: #0f172a;
  --shadow-sm: 0 1px 2px rgba(0,0,0,0.05);
  --shadow: 0 1px 3px rgba(0,0,0,0.1), 0 1px 2px rgba(0,0,0,0.06);
  --shadow-md: 0 4px 6px -1px rgba(0,0,0,0.1), 0 2px 4px -1px rgba(0,0,0,0.06);
  --shadow-lg: 0 10px 15px -3px rgba(0,0,0,0.1), 0 4px 6px -2px rgba(0,0,0,0.05);
  --shadow-xl: 0 20px 25px -5px rgba(0,0,0,0.1), 0 10px 10px -5px rgba(0,0,0,0.04);
  --radius: 12px;
  --radius-sm: 8px;
  --radius-xs: 4px;
  --transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'PingFang SC', 'Microsoft YaHei', sans-serif;
  background: var(--gray-50);
  color: var(--gray-800);
  line-height: 1.6;
  min-height: 100vh;
}

/* ===== Navbar ===== */
.navbar {
  background: #fff;
  border-bottom: 1px solid var(--gray-200);
  position: sticky;
  top: 0;
  z-index: 100;
  box-shadow: var(--shadow-sm);
}
.navbar-inner {
  max-width: 1280px;
  margin: 0 auto;
  padding: 0 24px;
  height: 64px;
  display: flex;
  align-items: center;
  justify-content: space-between;
}
.navbar-logo {
  display: flex;
  align-items: center;
  gap: 10px;
  font-size: 20px;
  font-weight: 700;
  color: var(--gray-900);
  text-decoration: none;
}
.navbar-logo svg { width: 28px; height: 28px; }
.navbar-logo span { background: linear-gradient(135deg, var(--primary), #8b5cf6); -webkit-background-clip: text; -webkit-text-fill-color: transparent; }
.navbar-links { display: flex; align-items: center; gap: 8px; }
.navbar-links a {
  padding: 8px 16px;
  border-radius: var(--radius-sm);
  color: var(--gray-600);
  text-decoration: none;
  font-size: 14px;
  font-weight: 500;
  transition: var(--transition);
}
.navbar-links a:hover { background: var(--gray-100); color: var(--gray-900); }
.navbar-links a.active { background: var(--primary-light); color: var(--primary); }

/* ===== Container ===== */
.container { max-width: 1280px; margin: 0 auto; padding: 32px 24px; }

/* ===== Hero ===== */
.hero {
  text-align: center;
  padding: 48px 0 40px;
}
.hero h1 { font-size: 36px; font-weight: 800; color: var(--gray-900); margin-bottom: 12px; }
.hero h1 span { background: linear-gradient(135deg, var(--primary), #8b5cf6); -webkit-background-clip: text; -webkit-text-fill-color: transparent; }
.hero p { font-size: 16px; color: var(--gray-500); max-width: 560px; margin: 0 auto 32px; }
.hero-search {
  max-width: 480px;
  margin: 0 auto;
  position: relative;
}
.hero-search input {
  width: 100%;
  padding: 14px 20px 14px 48px;
  border: 2px solid var(--gray-200);
  border-radius: var(--radius);
  font-size: 15px;
  transition: var(--transition);
  background: #fff;
  outline: none;
}
.hero-search input:focus { border-color: var(--primary); box-shadow: 0 0 0 4px rgba(79,108,247,0.1); }
.hero-search .search-icon {
  position: absolute;
  left: 16px;
  top: 50%;
  transform: translateY(-50%);
  color: var(--gray-400);
  font-size: 18px;
}

/* ===== Filters ===== */
.filters { display: flex; gap: 12px; margin-bottom: 32px; flex-wrap: wrap; }
.filter-btn {
  padding: 8px 20px;
  border: 2px solid var(--gray-200);
  border-radius: 999px;
  background: #fff;
  color: var(--gray-600);
  font-size: 13px;
  font-weight: 500;
  cursor: pointer;
  transition: var(--transition);
}
.filter-btn:hover { border-color: var(--primary); color: var(--primary); }
.filter-btn.active { background: var(--primary); border-color: var(--primary); color: #fff; }

/* ===== Quiz Grid ===== */
.quiz-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
  gap: 20px;
}
.quiz-card {
  background: #fff;
  border: 1px solid var(--gray-200);
  border-radius: var(--radius);
  padding: 24px;
  transition: var(--transition);
  cursor: pointer;
  position: relative;
  overflow: hidden;
}
.quiz-card::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 3px;
  background: linear-gradient(90deg, var(--primary), #8b5cf6);
  opacity: 0;
  transition: var(--transition);
}
.quiz-card:hover {
  border-color: var(--primary);
  box-shadow: var(--shadow-lg);
  transform: translateY(-2px);
}
.quiz-card:hover::before { opacity: 1; }
.quiz-card-category {
  display: inline-block;
  padding: 3px 10px;
  background: var(--primary-light);
  color: var(--primary);
  border-radius: 999px;
  font-size: 12px;
  font-weight: 600;
  margin-bottom: 12px;
}
.quiz-card h3 { font-size: 18px; font-weight: 700; margin-bottom: 8px; color: var(--gray-900); }
.quiz-card p { font-size: 14px; color: var(--gray-500); margin-bottom: 16px; display: -webkit-box; -webkit-line-clamp: 2; -webkit-box-orient: vertical; overflow: hidden; }
.quiz-card-meta { display: flex; gap: 16px; font-size: 13px; color: var(--gray-400); }
.quiz-card-meta span { display: flex; align-items: center; gap: 4px; }

/* ===== Empty State ===== */
.empty-state {
  text-align: center;
  padding: 60px 20px;
  color: var(--gray-400);
}
.empty-state svg { width: 64px; height: 64px; margin-bottom: 16px; opacity: 0.4; }
.empty-state h3 { font-size: 18px; color: var(--gray-600); margin-bottom: 8px; }
.empty-state p { font-size: 14px; }

/* ===== Loading ===== */
.loading { text-align: center; padding: 60px; color: var(--gray-400); }
.spinner {
  width: 36px; height: 36px;
  border: 3px solid var(--gray-200);
  border-top-color: var(--primary);
  border-radius: 50%;
  animation: spin 0.8s linear infinite;
  margin: 0 auto 16px;
}
@keyframes spin { to { transform: rotate(360deg); } }

/* ===== Modal ===== */
.modal-overlay {
  position: fixed;
  inset: 0;
  background: rgba(0,0,0,0.5);
  backdrop-filter: blur(4px);
  z-index: 1000;
  display: none;
  align-items: center;
  justify-content: center;
  padding: 20px;
}
.modal-overlay.active { display: flex; }
.modal {
  background: #fff;
  border-radius: 16px;
  box-shadow: var(--shadow-xl);
  width: 100%;
  max-width: 800px;
  max-height: 90vh;
  display: flex;
  flex-direction: column;
  animation: modalIn 0.3s ease;
}
@keyframes modalIn {
  from { opacity: 0; transform: scale(0.95) translateY(10px); }
  to { opacity: 1; transform: scale(1) translateY(0); }
}
.modal-header {
  padding: 20px 24px;
  border-bottom: 1px solid var(--gray-200);
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-shrink: 0;
}
.modal-header h2 { font-size: 18px; font-weight: 700; }
.mode-card:hover { border-color: var(--primary) !important; box-shadow: var(--shadow-md); transform: translateY(-2px); }
.mode-card.selected { border-color: var(--primary) !important; background: var(--primary-light) !important; }
.modal-close {
  width: 32px; height: 32px;
  border: none;
  background: var(--gray-100);
  border-radius: 50%;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--gray-500);
  font-size: 18px;
  transition: var(--transition);
}
.modal-close:hover { background: var(--gray-200); color: var(--gray-700); }
.modal-body { padding: 24px; overflow-y: auto; flex: 1; }
.modal-footer {
  padding: 16px 24px;
  border-top: 1px solid var(--gray-200);
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-shrink: 0;
}

/* ===== Quiz Taking ===== */
.quiz-progress {
  display: flex;
  align-items: center;
  gap: 12px;
  margin-bottom: 24px;
}
.quiz-progress-bar {
  flex: 1;
  height: 6px;
  background: var(--gray-200);
  border-radius: 3px;
  overflow: hidden;
}
.quiz-progress-fill {
  height: 100%;
  background: linear-gradient(90deg, var(--primary), #8b5cf6);
  border-radius: 3px;
  transition: width 0.5s ease;
}
.quiz-progress-text { font-size: 13px; color: var(--gray-500); font-weight: 500; white-space: nowrap; }
.quiz-timer {
  display: flex;
  align-items: center;
  gap: 6px;
  font-size: 14px;
  font-weight: 600;
  color: var(--gray-700);
}
.quiz-timer.warning { color: var(--danger); }

.question-card {
  background: var(--gray-50);
  border: 1px solid var(--gray-200);
  border-radius: var(--radius);
  padding: 24px;
  margin-bottom: 20px;
}
.question-number {
  display: inline-block;
  padding: 2px 10px;
  background: var(--primary);
  color: #fff;
  border-radius: 999px;
  font-size: 12px;
  font-weight: 600;
  margin-bottom: 12px;
}
.question-type-badge {
  display: inline-block;
  padding: 2px 10px;
  background: var(--gray-200);
  color: var(--gray-600);
  border-radius: 999px;
  font-size: 12px;
  font-weight: 500;
  margin-left: 8px;
}
.question-text {
  font-size: 16px;
  font-weight: 600;
  color: var(--gray-900);
  margin-bottom: 20px;
  line-height: 1.7;
}

.options { display: flex; flex-direction: column; gap: 10px; }
.option {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 14px 16px;
  border: 2px solid var(--gray-200);
  border-radius: var(--radius-sm);
  cursor: pointer;
  transition: var(--transition);
  background: #fff;
}
.option:hover { border-color: var(--primary); background: var(--primary-light); }
.option.selected { border-color: var(--primary); background: var(--primary-light); }
.option input[type="radio"], .option input[type="checkbox"] {
  width: 18px; height: 18px;
  accent-color: var(--primary);
  flex-shrink: 0;
}
.option-label { font-size: 14px; color: var(--gray-700); flex: 1; user-select: none; }

.fill-input {
  width: 100%;
  padding: 12px 16px;
  border: 2px solid var(--gray-200);
  border-radius: var(--radius-sm);
  font-size: 15px;
  outline: none;
  transition: var(--transition);
}
.fill-input:focus { border-color: var(--primary); box-shadow: 0 0 0 4px rgba(79,108,247,0.1); }

/* ===== Results ===== */
.results-summary {
  text-align: center;
  padding: 32px 0;
}
.results-score {
  font-size: 56px;
  font-weight: 800;
  background: linear-gradient(135deg, var(--primary), #8b5cf6);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  line-height: 1;
}
.results-label { font-size: 14px; color: var(--gray-500); margin-top: 8px; }
.results-passed {
  display: inline-block;
  padding: 6px 16px;
  border-radius: 999px;
  font-size: 14px;
  font-weight: 600;
  margin-top: 12px;
}
.results-passed.pass { background: var(--success-light); color: var(--success); }
.results-passed.fail { background: var(--danger-light); color: var(--danger); }
.results-meta {
  display: flex;
  justify-content: center;
  gap: 32px;
  margin-top: 24px;
}
.results-meta-item { text-align: center; }
.results-meta-value { font-size: 24px; font-weight: 700; color: var(--gray-900); }
.results-meta-label { font-size: 12px; color: var(--gray-500); margin-top: 2px; }

.result-item {
  padding: 16px;
  border-radius: var(--radius-sm);
  margin-bottom: 12px;
  border: 1px solid var(--gray-200);
}
.result-item.correct { border-left: 4px solid var(--success); background: var(--success-light); }
.result-item.wrong { border-left: 4px solid var(--danger); background: var(--danger-light); }
.result-question { font-size: 14px; font-weight: 600; margin-bottom: 8px; }
.result-answer { font-size: 13px; color: var(--gray-600); margin-bottom: 4px; }
.result-answer .correct-text { color: var(--success); font-weight: 600; }
.result-answer .wrong-text { color: var(--danger); font-weight: 600; }
.result-explanation {
  font-size: 13px;
  color: var(--gray-500);
  margin-top: 8px;
  padding: 8px 12px;
  background: #fff;
  border-radius: var(--radius-xs);
  border: 1px solid var(--gray-200);
}

/* ===== Buttons ===== */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 6px;
  padding: 10px 24px;
  border: none;
  border-radius: var(--radius-sm);
  font-size: 14px;
  font-weight: 600;
  cursor: pointer;
  transition: var(--transition);
  text-decoration: none;
}
.btn-primary { background: var(--primary); color: #fff; }
.btn-primary:hover { background: var(--primary-dark); box-shadow: var(--shadow-md); }
.btn-success { background: var(--success); color: #fff; }
.btn-success:hover { background: #16a34a; box-shadow: var(--shadow-md); }
.btn-danger { background: var(--danger); color: #fff; }
.btn-danger:hover { background: #dc2626; box-shadow: var(--shadow-md); }
.btn-ghost { background: transparent; color: var(--gray-600); }
.btn-ghost:hover { background: var(--gray-100); }
.btn-outline { background: transparent; border: 2px solid var(--gray-200); color: var(--gray-700); }
.btn-outline:hover { border-color: var(--primary); color: var(--primary); }
.btn-sm { padding: 6px 14px; font-size: 13px; }
.btn-block { width: 100%; }
.btn:disabled { opacity: 0.5; cursor: not-allowed; }

/* ===== Notification ===== */
.toast {
  position: fixed;
  bottom: 24px;
  right: 24px;
  height: 40px;
  border-radius: 20px;
  color: #fff;
  font-size: 14px;
  font-weight: 500;
  z-index: 2000;
  box-shadow: var(--shadow-lg);
  display: flex;
  align-items: center;
  overflow: hidden;
  max-width: 40px;
  animation: toastGrow 0.5s cubic-bezier(0.34, 1.56, 0.64, 1) forwards;
}
.toast.success { background: var(--success); }
.toast.error { background: var(--danger); }
.toast.info { background: var(--primary); }
.toast.warning { background: var(--warning); }

@keyframes toastGrow {
  0% { max-width: 40px; }
  100% { max-width: 420px; }
}

.toast-text {
  white-space: nowrap;
  padding: 0 24px;
  opacity: 0;
  animation: textAppear 0.15s ease 0.2s forwards;
}

@keyframes textAppear {
  from { opacity: 0; }
  to { opacity: 1; }
}

/* ===== Practice Mode Highlighting ===== */
.option.correct-answer {
  border-color: var(--success) !important;
  background: var(--success-light) !important;
}
.option.correct-answer .option-label {
  color: var(--success) !important;
  font-weight: 700 !important;
}
.option.wrong-answer {
  border-color: var(--danger) !important;
  background: var(--danger-light) !important;
}
.option.wrong-answer .option-label {
  color: var(--danger) !important;
  font-weight: 700 !important;
}
.practice-result {
  margin-top: 16px;
  padding: 16px;
  border-radius: 8px;
  display: flex;
  align-items: flex-start;
  gap: 12px;
}
.practice-result.wrong {
  background: var(--danger-light);
  border: 1px solid var(--danger);
}
.practice-result-icon {
  font-size: 24px;
  line-height: 1;
}

/* ===== Responsive ===== */
@media (max-width: 768px) {
  body { font-size: 16px; }
  .container { padding: 32px 24px; }
  .navbar-inner { padding: 0 24px; height: 64px; }
  .navbar-logo { font-size: 20px; gap: 12px; }
  .navbar-logo svg { width: 28px; height: 28px; }
  .navbar-links a { padding: 10px 18px; font-size: 15px; }

  .hero { padding: 40px 0 32px; }
  .hero h1 { font-size: 30px; margin-bottom: 12px; }
  .hero p { font-size: 16px; margin-bottom: 28px; }
  .hero-search { max-width: 100%; }
  .hero-search input { padding: 16px 24px 16px 48px; font-size: 16px; border-radius: 16px; }
  .hero-search .search-icon { left: 18px; font-size: 20px; }

  .filters { gap: 12px; margin-bottom: 28px; flex-wrap: wrap; padding-bottom: 0; overflow-x: visible; }
  .filter-btn { padding: 10px 22px; font-size: 14px; white-space: nowrap; flex-shrink: 0; }

  .quiz-grid { grid-template-columns: 1fr; gap: 20px; }
  .quiz-card { padding: 24px; }
  .quiz-card h3 { font-size: 18px; }
  .quiz-card p { font-size: 14px; -webkit-line-clamp: 2; margin-bottom: 16px; }
  .quiz-card-meta { font-size: 13px; gap: 16px; flex-wrap: wrap; }

  .modal-overlay { padding: 0; align-items: flex-end; }
  .modal-overlay.active { align-items: flex-end; }
  .modal { margin: 0; max-height: 92vh; max-width: 100%; border-radius: 24px 24px 0 0; }
  .modal-header { padding: 24px 24px 16px; }
  .modal-header h2 { font-size: 18px; }
  .modal-body { padding: 16px 24px 24px; }
  .modal-footer { padding: 16px 24px 24px; gap: 12px; flex-wrap: wrap; }
  .modal-footer #footerLeft, .modal-footer #footerRight, .modal-footer #footerCenter { flex: 1; }
  .modal-footer .btn { width: 100%; font-size: 15px; padding: 14px 16px; border-radius: 12px; }
  .modal-footer #footerCenter .btn { font-size: 16px; padding: 16px; }

  #quizContent > div:first-child { gap: 14px !important; margin-bottom: 24px !important; }
  .quiz-progress { min-width: 140px !important; }
  .quiz-progress-text { font-size: 14px; }
  .quiz-timer { font-size: 15px; }

  .question-card { padding: 24px; margin-bottom: 20px; border-radius: 16px; }
  .question-text { font-size: 17px; margin-bottom: 24px; line-height: 1.8; }
  .option { padding: 16px 18px; gap: 14px; border-radius: 12px; min-height: 56px; }
  .option input[type="radio"], .option input[type="checkbox"] { width: 24px; height: 24px; min-width: 24px; }
  .option-label { font-size: 16px; }
  .fill-input { padding: 14px 18px; font-size: 16px; border-radius: 12px; min-height: 52px; }

  .results-score { font-size: 48px; }
  .results-summary { padding: 24px 0; }
  .results-meta { gap: 28px; }
  .results-meta-item { min-width: 80px; }
  .results-meta-value { font-size: 24px; }
  .result-item { padding: 16px; border-radius: 12px; }
  .result-question { font-size: 15px; }

  .practice-result { padding: 16px; gap: 12px; font-size: 14px; border-radius: 12px; }
  .practice-result-icon { font-size: 24px; }

  #modeModal .modal-body > div:first-child { grid-template-columns: 1fr !important; }
  .mode-card { padding: 24px !important; border-radius: 16px !important; }
  .mode-card h3 { font-size: 17px !important; }
  .mode-card p { font-size: 14px !important; }
  #typeCheckboxes { flex-wrap: wrap !important; gap: 12px; }
  #typeCheckboxes label { white-space: nowrap; flex-shrink: 0; padding: 12px 20px; font-size: 15px; border-radius: 999px; }

  .toast { left: 20px; right: 20px; bottom: 20px; top: auto; height: 44px; border-radius: 22px; max-width: 44px; font-size: 15px; animation-name: toastGrowMobile; }
  @keyframes toastGrowMobile {
    0% { max-width: 44px; }
    100% { max-width: calc(100vw - 40px); }
  }
  .toast-text { padding: 0 20px; }
}

@media (max-width: 480px) {
  .container { padding: 20px 16px; }
  .hero h1 { font-size: 24px; }
  .hero { padding: 28px 0 24px; }
  .navbar-links a { padding: 8px 14px; font-size: 14px; }
  .question-card { padding: 18px; }
  .option { padding: 14px 16px; min-height: 50px; }
  .option-label { font-size: 15px; }
  .modal-header { padding: 20px 20px 12px; }
  .modal-header h2 { font-size: 17px; }
  .modal-body { padding: 12px 20px 20px; }
  .modal-footer { padding: 12px 20px 20px; }
  .results-score { font-size: 40px; }
  .results-meta { gap: 20px; }
  .quiz-card { padding: 20px; }
}