/* ========== 全局样式 ========== */
* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

:root {
  --primary: #4f46e5;
  --primary-light: #6366f1;
  --primary-dark: #4338ca;
  --primary-bg: #eef2ff;
  --success: #16a34a;
  --success-bg: #f0fdf4;
  --success-border: #bbf7d0;
  --danger: #dc2626;
  --danger-bg: #fef2f2;
  --danger-border: #fecaca;
  --warning: #f59e0b;
  --warning-bg: #fffbeb;
  --info: #0ea5e9;
  --info-bg: #f0f9ff;
  --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: 12px;
  --radius-sm: 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(0,0,0,0.1), 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, 'PingFang SC', 'Microsoft YaHei', sans-serif;
  background: var(--gray-50);
  color: var(--gray-800);
  line-height: 1.6;
  min-height: 100vh;
}

/* ========== 登录页 ========== */
.login-container {
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  padding: 20px;
}

.login-card {
  background: white;
  border-radius: 20px;
  box-shadow: var(--shadow-lg);
  padding: 40px;
  width: 100%;
  max-width: 420px;
}

.login-card h1 {
  text-align: center;
  font-size: 24px;
  color: var(--gray-800);
  margin-bottom: 8px;
}

.login-card .subtitle {
  text-align: center;
  color: var(--gray-500);
  font-size: 14px;
  margin-bottom: 32px;
}

.login-tabs {
  display: flex;
  gap: 8px;
  margin-bottom: 24px;
  background: var(--gray-100);
  border-radius: var(--radius-sm);
  padding: 4px;
}

.login-tab {
  flex: 1;
  padding: 10px;
  text-align: center;
  border-radius: 6px;
  cursor: pointer;
  font-size: 14px;
  font-weight: 500;
  color: var(--gray-500);
  transition: all 0.2s;
}

.login-tab.active {
  background: white;
  color: var(--primary);
  box-shadow: var(--shadow);
}

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

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

.form-group input,
.form-group select {
  width: 100%;
  padding: 10px 14px;
  border: 1.5px solid var(--gray-200);
  border-radius: var(--radius-sm);
  font-size: 14px;
  color: var(--gray-800);
  transition: border-color 0.2s, box-shadow 0.2s;
  outline: none;
  background: white;
}

.form-group input:focus,
.form-group select:focus {
  border-color: var(--primary);
  box-shadow: 0 0 0 3px rgba(79, 70, 229, 0.1);
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 6px;
  padding: 10px 20px;
  border: none;
  border-radius: var(--radius-sm);
  font-size: 14px;
  font-weight: 500;
  cursor: pointer;
  transition: all 0.2s;
  text-decoration: none;
  white-space: nowrap;
}

.btn-primary {
  background: var(--primary);
  color: white;
}

.btn-primary:hover {
  background: var(--primary-dark);
}

.btn-secondary {
  background: var(--gray-100);
  color: var(--gray-700);
}

.btn-secondary:hover {
  background: var(--gray-200);
}

.btn-success {
  background: var(--success);
  color: white;
}

.btn-danger {
  background: var(--danger);
  color: white;
}

.btn-warning {
  background: var(--warning);
  color: white;
}

.btn-block {
  width: 100%;
}

.btn-lg {
  padding: 12px 24px;
  font-size: 16px;
}

.btn-sm {
  padding: 6px 12px;
  font-size: 12px;
}

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

.login-hint {
  margin-top: 16px;
  padding: 12px;
  background: var(--info-bg);
  border-radius: var(--radius-sm);
  font-size: 12px;
  color: var(--gray-600);
  text-align: center;
}

/* ========== 主布局 ========== */
.app-layout {
  display: flex;
  min-height: 100vh;
}

.sidebar {
  width: 240px;
  background: white;
  border-right: 1px solid var(--gray-200);
  padding: 20px 0;
  position: fixed;
  height: 100vh;
  overflow-y: auto;
  z-index: 100;
}

.sidebar-header {
  padding: 0 20px 20px;
  border-bottom: 1px solid var(--gray-200);
}

.sidebar-header h2 {
  font-size: 18px;
  color: var(--gray-800);
  margin-bottom: 4px;
}

.sidebar-header .role-badge {
  display: inline-block;
  padding: 2px 10px;
  border-radius: 12px;
  font-size: 12px;
  font-weight: 500;
}

.role-badge.teacher {
  background: var(--primary-bg);
  color: var(--primary);
}

.role-badge.student {
  background: var(--success-bg);
  color: var(--success);
}

.sidebar-nav {
  padding: 12px 0;
}

.nav-item {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 10px 20px;
  color: var(--gray-600);
  font-size: 14px;
  cursor: pointer;
  transition: all 0.2s;
  border-left: 3px solid transparent;
}

.nav-item:hover {
  background: var(--gray-50);
  color: var(--gray-800);
}

.nav-item.active {
  background: var(--primary-bg);
  color: var(--primary);
  border-left-color: var(--primary);
  font-weight: 500;
}

.nav-item .icon {
  font-size: 18px;
  width: 24px;
  text-align: center;
}

.sidebar-footer {
  position: absolute;
  bottom: 0;
  left: 0;
  right: 0;
  padding: 16px 20px;
  border-top: 1px solid var(--gray-200);
  background: white;
}

.main-content {
  flex: 1;
  margin-left: 240px;
  padding: 24px 32px;
  max-width: calc(100% - 240px);
}

.page-header {
  margin-bottom: 24px;
}

.page-header h1 {
  font-size: 24px;
  color: var(--gray-800);
  margin-bottom: 4px;
}

.page-header .breadcrumb {
  font-size: 13px;
  color: var(--gray-500);
}

/* ========== 卡片 ========== */
.card {
  background: white;
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: 24px;
  margin-bottom: 20px;
}

.card-title {
  font-size: 16px;
  font-weight: 600;
  color: var(--gray-800);
  margin-bottom: 16px;
  padding-bottom: 12px;
  border-bottom: 1px solid var(--gray-100);
}

/* ========== 统计卡片 ========== */
.stats-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: 16px;
  margin-bottom: 24px;
}

.stat-card {
  background: white;
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: 20px;
  display: flex;
  align-items: center;
  gap: 16px;
}

.stat-icon {
  width: 48px;
  height: 48px;
  border-radius: 12px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 24px;
}

.stat-icon.blue { background: var(--info-bg); color: var(--info); }
.stat-icon.green { background: var(--success-bg); color: var(--success); }
.stat-icon.red { background: var(--danger-bg); color: var(--danger); }
.stat-icon.purple { background: var(--primary-bg); color: var(--primary); }
.stat-icon.orange { background: var(--warning-bg); color: var(--warning); }

.stat-info h3 {
  font-size: 28px;
  font-weight: 700;
  color: var(--gray-800);
  line-height: 1.2;
}

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

/* ========== 单元选择 ========== */
.unit-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 16px;
}

.unit-card {
  background: white;
  border: 2px solid var(--gray-200);
  border-radius: var(--radius);
  padding: 20px;
  cursor: pointer;
  transition: all 0.2s;
}

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

.unit-card.selected {
  border-color: var(--primary);
  background: var(--primary-bg);
}

.unit-card .module-tag {
  display: inline-block;
  padding: 2px 8px;
  background: var(--gray-100);
  border-radius: 4px;
  font-size: 11px;
  color: var(--gray-500);
  margin-bottom: 8px;
}

.unit-card h3 {
  font-size: 15px;
  color: var(--gray-800);
  margin-bottom: 8px;
}

.unit-card .unit-meta {
  font-size: 13px;
  color: var(--gray-500);
  display: flex;
  align-items: center;
  gap: 8px;
}

.unit-card .unit-number {
  width: 32px;
  height: 32px;
  border-radius: 8px;
  background: var(--primary);
  color: white;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 14px;
  font-weight: 600;
  margin-bottom: 12px;
}

/* ========== 答题界面 ========== */
.quiz-container {
  max-width: 800px;
  margin: 0 auto;
}

.quiz-progress-bar {
  height: 8px;
  background: var(--gray-200);
  border-radius: 4px;
  overflow: hidden;
  margin-bottom: 8px;
}

.quiz-progress-fill {
  height: 100%;
  background: var(--primary);
  border-radius: 4px;
  transition: width 0.3s ease;
}

.quiz-progress-info {
  display: flex;
  justify-content: space-between;
  font-size: 13px;
  color: var(--gray-500);
  margin-bottom: 24px;
}

.question-card {
  background: white;
  border-radius: var(--radius);
  box-shadow: var(--shadow-md);
  padding: 32px;
  margin-bottom: 20px;
}

.question-number {
  display: inline-block;
  padding: 4px 12px;
  background: var(--primary-bg);
  color: var(--primary);
  border-radius: 6px;
  font-size: 13px;
  font-weight: 500;
  margin-bottom: 16px;
}

.question-unit-tag {
  display: inline-block;
  padding: 4px 12px;
  background: var(--gray-100);
  color: var(--gray-600);
  border-radius: 6px;
  font-size: 12px;
  margin-bottom: 16px;
  margin-left: 8px;
}

.question-text {
  font-size: 18px;
  color: var(--gray-800);
  line-height: 1.6;
  margin-bottom: 24px;
  font-weight: 500;
}

.options-list {
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.option-item {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 14px 18px;
  border: 2px solid var(--gray-200);
  border-radius: var(--radius-sm);
  cursor: pointer;
  transition: all 0.2s;
}

.option-item:hover {
  border-color: var(--primary-light);
  background: var(--primary-bg);
}

.option-item.selected {
  border-color: var(--primary);
  background: var(--primary-bg);
}

.option-item.correct {
  border-color: var(--success);
  background: var(--success-bg);
}

.option-item.wrong {
  border-color: var(--danger);
  background: var(--danger-bg);
}

.option-label {
  width: 32px;
  height: 32px;
  border-radius: 50%;
  background: var(--gray-100);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 14px;
  font-weight: 600;
  color: var(--gray-600);
  flex-shrink: 0;
}

.option-item.selected .option-label {
  background: var(--primary);
  color: white;
}

.option-item.correct .option-label {
  background: var(--success);
  color: white;
}

.option-item.wrong .option-label {
  background: var(--danger);
  color: white;
}

.option-text {
  font-size: 15px;
  color: var(--gray-700);
}

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

.answer-feedback {
  margin-top: 16px;
  padding: 12px 16px;
  border-radius: var(--radius-sm);
  font-size: 14px;
  display: none;
}

.answer-feedback.show {
  display: block;
}

.answer-feedback.correct {
  background: var(--success-bg);
  color: var(--success);
  border: 1px solid var(--success-border);
}

.answer-feedback.wrong {
  background: var(--danger-bg);
  color: var(--danger);
  border: 1px solid var(--danger-border);
}

/* ========== 结果页 ========== */
.result-container {
  max-width: 800px;
  margin: 0 auto;
}

.result-header {
  text-align: center;
  margin-bottom: 32px;
}

.result-score {
  width: 120px;
  height: 120px;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  margin: 0 auto 16px;
  font-size: 36px;
  font-weight: 700;
}

.result-score.pass {
  background: var(--success-bg);
  color: var(--success);
  border: 4px solid var(--success);
}

.result-score.fail {
  background: var(--danger-bg);
  color: var(--danger);
  border: 4px solid var(--danger);
}

.result-summary {
  display: flex;
  justify-content: center;
  gap: 32px;
  margin-bottom: 32px;
}

.result-summary-item {
  text-align: center;
}

.result-summary-item h3 {
  font-size: 32px;
  font-weight: 700;
}

.result-summary-item p {
  font-size: 13px;
  color: var(--gray-500);
}

.result-summary-item.correct h3 { color: var(--success); }
.result-summary-item.wrong h3 { color: var(--danger); }
.result-summary-item.total h3 { color: var(--primary); }

/* 表格 */
.table-container {
  overflow-x: auto;
}

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

table th {
  text-align: left;
  padding: 12px 16px;
  background: var(--gray-50);
  color: var(--gray-600);
  font-weight: 600;
  font-size: 13px;
  border-bottom: 2px solid var(--gray-200);
  white-space: nowrap;
}

table td {
  padding: 12px 16px;
  border-bottom: 1px solid var(--gray-100);
  color: var(--gray-700);
}

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

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

.badge-success { background: var(--success-bg); color: var(--success); }
.badge-danger { background: var(--danger-bg); color: var(--danger); }
.badge-info { background: var(--info-bg); color: var(--info); }
.badge-warning { background: var(--warning-bg); color: var(--warning); }

/* 模态框 */
.modal-overlay {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: rgba(0, 0, 0, 0.5);
  display: none;
  align-items: center;
  justify-content: center;
  z-index: 1000;
  padding: 20px;
}

.modal-overlay.show {
  display: flex;
}

.modal {
  background: white;
  border-radius: var(--radius);
  box-shadow: var(--shadow-lg);
  width: 100%;
  max-width: 500px;
  max-height: 90vh;
  overflow-y: auto;
}

.modal-header {
  padding: 20px 24px;
  border-bottom: 1px solid var(--gray-200);
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.modal-header h3 {
  font-size: 18px;
  color: var(--gray-800);
}

.modal-close {
  background: none;
  border: none;
  font-size: 24px;
  color: var(--gray-400);
  cursor: pointer;
  padding: 0;
  width: 32px;
  height: 32px;
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: 6px;
}

.modal-close:hover {
  background: var(--gray-100);
  color: var(--gray-600);
}

.modal-body {
  padding: 24px;
}

.modal-footer {
  padding: 16px 24px;
  border-top: 1px solid var(--gray-200);
  display: flex;
  justify-content: flex-end;
  gap: 12px;
}

/* 图表容器 */
.chart-container {
  position: relative;
  width: 100%;
  max-width: 600px;
  margin: 0 auto;
}

/* 空状态 */
.empty-state {
  text-align: center;
  padding: 60px 20px;
  color: var(--gray-400);
}

.empty-state .icon {
  font-size: 48px;
  margin-bottom: 16px;
}

.empty-state p {
  font-size: 14px;
}

/* Toast 通知 */
.toast {
  position: fixed;
  top: 20px;
  right: 20px;
  padding: 12px 20px;
  border-radius: var(--radius-sm);
  font-size: 14px;
  font-weight: 500;
  z-index: 2000;
  display: flex;
  align-items: center;
  gap: 8px;
  box-shadow: var(--shadow-lg);
  transform: translateX(400px);
  transition: transform 0.3s ease;
}

.toast.show {
  transform: translateX(0);
}

.toast.success { background: var(--success); color: white; }
.toast.error { background: var(--danger); color: white; }
.toast.info { background: var(--info); color: white; }

/* 响应式 */
@media (max-width: 768px) {
  .sidebar {
    transform: translateX(-100%);
    transition: transform 0.3s;
  }
  .sidebar.show {
    transform: translateX(0);
  }
  .main-content {
    margin-left: 0;
    max-width: 100%;
    padding: 16px;
  }
  .stats-grid {
    grid-template-columns: 1fr;
  }
  .unit-grid {
    grid-template-columns: 1fr;
  }
}

/* 工具类 */
.text-center { text-align: center; }
.text-right { text-align: right; }
.mt-16 { margin-top: 16px; }
.mt-24 { margin-top: 24px; }
.mb-16 { margin-bottom: 16px; }
.mb-24 { margin-bottom: 24px; }
.flex { display: flex; }
.flex-between { display: flex; justify-content: space-between; align-items: center; }
.gap-8 { gap: 8px; }
.gap-12 { gap: 12px; }
.gap-16 { gap: 16px; }
.flex-wrap { flex-wrap: wrap; }
.hidden { display: none !important; }
.w-full { width: 100%; }

/* 进度环 */
.progress-ring {
  position: relative;
  width: 100px;
  height: 100px;
}

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

.progress-ring circle {
  fill: none;
  stroke-width: 8;
  stroke-linecap: round;
}

.progress-ring .bg {
  stroke: var(--gray-200);
}

.progress-ring .fg {
  stroke: var(--primary);
  transition: stroke-dashoffset 0.5s ease;
}

.progress-ring .text {
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  font-size: 20px;
  font-weight: 700;
  color: var(--gray-800);
}

/* 单元统计条 */
.unit-stat-bar {
  margin-bottom: 16px;
}

.unit-stat-bar .label {
  display: flex;
  justify-content: space-between;
  margin-bottom: 4px;
  font-size: 13px;
}

.unit-stat-bar .bar {
  height: 24px;
  background: var(--gray-100);
  border-radius: 6px;
  overflow: hidden;
  display: flex;
}

.unit-stat-bar .bar-correct {
  background: var(--success);
  transition: width 0.5s ease;
}

.unit-stat-bar .bar-wrong {
  background: var(--danger);
  transition: width 0.5s ease;
}

/* 返回按钮 */
.back-btn {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 6px 14px;
  background: var(--gray-100);
  border: none;
  border-radius: var(--radius-sm);
  color: var(--gray-600);
  font-size: 13px;
  font-weight: 500;
  cursor: pointer;
  transition: all 0.2s;
}

.back-btn:hover {
  background: var(--gray-200);
  color: var(--gray-800);
}

.page-header-row {
  display: flex;
  align-items: center;
  gap: 12px;
  margin-bottom: 4px;
}

.page-header-row h1 {
  margin-bottom: 0;
}

/* 文件上传区域 */
.upload-zone {
  border: 2px dashed var(--gray-300);
  border-radius: var(--radius);
  padding: 40px 20px;
  text-align: center;
  cursor: pointer;
  transition: all 0.2s;
  background: var(--gray-50);
}

.upload-zone:hover {
  border-color: var(--primary);
  background: var(--primary-bg);
}

.upload-zone .upload-icon {
  font-size: 48px;
  margin-bottom: 12px;
}

.upload-zone p {
  font-size: 14px;
  color: var(--gray-500);
  margin-bottom: 4px;
}

.upload-zone .hint {
  font-size: 12px;
  color: var(--gray-400);
}

.upload-zone input[type="file"] {
  display: none;
}

/* 导入预览表格 */
.import-preview {
  max-height: 350px;
  overflow-y: auto;
  border: 1px solid var(--gray-200);
  border-radius: var(--radius-sm);
  margin-top: 16px;
}

.import-preview table {
  margin: 0;
}

.import-preview table th {
  position: sticky;
  top: 0;
  z-index: 1;
}

.import-summary {
  display: flex;
  gap: 16px;
  margin-top: 8px;
  padding: 12px;
  background: var(--gray-50);
  border-radius: var(--radius-sm);
  font-size: 13px;
}

.import-summary .item {
  display: flex;
  align-items: center;
  gap: 4px;
}

.import-summary .item.success { color: var(--success); }
.import-summary .item.fail { color: var(--danger); }

/* 导入格式提示 */
.format-hint {
  background: var(--info-bg);
  border: 1px solid #bae6fd;
  border-radius: var(--radius-sm);
  padding: 16px;
  margin-top: 16px;
  font-size: 13px;
  line-height: 1.8;
}

.format-hint h4 {
  color: var(--info);
  margin-bottom: 8px;
  font-size: 14px;
}

.format-hint code {
  background: white;
  padding: 2px 6px;
  border-radius: 3px;
  font-size: 12px;
  color: var(--danger);
}

/* 试题库统计 */
.question-bank-stats {
  display: flex;
  gap: 16px;
  flex-wrap: wrap;
  margin-bottom: 20px;
}

.question-bank-stats .stat-item {
  background: white;
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: 16px 24px;
  display: flex;
  align-items: center;
  gap: 12px;
}

.question-bank-stats .stat-item .num {
  font-size: 28px;
  font-weight: 700;
  color: var(--primary);
}

.question-bank-stats .stat-item .label {
  font-size: 13px;
  color: var(--gray-500);
}

/* 筛选栏 */
.filter-bar {
  display: flex;
  gap: 12px;
  align-items: center;
  margin-bottom: 20px;
  flex-wrap: wrap;
}

.filter-bar select,
.filter-bar input {
  padding: 8px 12px;
  border: 1.5px solid var(--gray-200);
  border-radius: var(--radius-sm);
  font-size: 14px;
  outline: none;
  background: white;
}

.filter-bar select:focus,
.filter-bar input:focus {
  border-color: var(--primary);
}