/* ============================================
   记忆卡片 - 样式表
   ============================================ */

/* ==================== 变量与主题 ==================== */

:root {
  --primary: #6366f1;
  --primary-light: #818cf8;
  --primary-dark: #4f46e5;
  --primary-bg: rgba(99, 102, 241, 0.08);

  --bg: #f8fafc;
  --bg-elevated: #ffffff;
  --bg-hover: #f1f5f9;
  --sidebar-bg: #ffffff;
  --text: #1e293b;
  --text-secondary: #64748b;
  --text-muted: #94a3b8;
  --border: #e2e8f0;
  --border-light: #f1f5f9;

  --success: #22c55e;
  --success-bg: rgba(34, 197, 94, 0.1);
  --warning: #f59e0b;
  --warning-bg: rgba(245, 158, 11, 0.1);
  --danger: #ef4444;
  --danger-bg: rgba(239, 68, 68, 0.1);
  --info: #3b82f6;
  --info-bg: rgba(59, 130, 246, 0.1);

  --shadow-sm: 0 1px 2px rgba(0,0,0,0.04);
  --shadow: 0 1px 3px rgba(0,0,0,0.06), 0 1px 2px rgba(0,0,0,0.04);
  --shadow-md: 0 4px 6px -1px rgba(0,0,0,0.07), 0 2px 4px -2px rgba(0,0,0,0.05);
  --shadow-lg: 0 10px 15px -3px rgba(0,0,0,0.08), 0 4px 6px -4px rgba(0,0,0,0.05);

  --radius: 8px;
  --radius-lg: 12px;
  --radius-xl: 16px;

  --sidebar-width: 240px;
  --transition: 0.2s ease;

  --mastery-0: #94a3b8;
  --mastery-1: #ef4444;
  --mastery-2: #f59e0b;
  --mastery-3: #3b82f6;
  --mastery-4: #22c55e;
}

[data-theme="dark"] {
  --primary: #818cf8;
  --primary-light: #a5b4fc;
  --primary-dark: #6366f1;
  --primary-bg: rgba(129, 140, 248, 0.12);

  --bg: #0f172a;
  --bg-elevated: #1e293b;
  --bg-hover: #334155;
  --sidebar-bg: #1e293b;
  --text: #f1f5f9;
  --text-secondary: #94a3b8;
  --text-muted: #64748b;
  --border: #334155;
  --border-light: #1e293b;

  --shadow-sm: 0 1px 2px rgba(0,0,0,0.2);
  --shadow: 0 1px 3px rgba(0,0,0,0.3), 0 1px 2px rgba(0,0,0,0.2);
  --shadow-md: 0 4px 6px -1px rgba(0,0,0,0.3), 0 2px 4px -2px rgba(0,0,0,0.2);
  --shadow-lg: 0 10px 15px -3px rgba(0,0,0,0.4), 0 4px 6px -4px rgba(0,0,0,0.2);
}

/* ==================== 重置与基础 ==================== */

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

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Noto Sans SC", "PingFang SC", "Microsoft YaHei", sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
  transition: background var(--transition), color var(--transition);
}

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

/* ==================== 布局 ==================== */

#app {
  display: flex;
  min-height: 100vh;
}

/* ==================== 侧边栏 ==================== */

.sidebar {
  width: var(--sidebar-width);
  background: var(--sidebar-bg);
  border-right: 1px solid var(--border);
  display: flex;
  flex-direction: column;
  position: fixed;
  top: 0;
  left: 0;
  bottom: 0;
  z-index: 100;
  transition: transform var(--transition);
}

.sidebar-header {
  padding: 20px 16px;
  display: flex;
  align-items: center;
  gap: 12px;
  border-bottom: 1px solid var(--border);
}

.logo-icon { font-size: 28px; }
.logo-text { display: flex; flex-direction: column; }
.logo-title { font-size: 16px; font-weight: 700; color: var(--text); }
.logo-subtitle { font-size: 11px; color: var(--text-muted); }

.nav {
  flex: 1;
  padding: 12px 8px;
  overflow-y: auto;
}

.nav-item {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 10px 12px;
  border-radius: var(--radius);
  color: var(--text-secondary);
  font-size: 14px;
  font-weight: 500;
  transition: all var(--transition);
  margin-bottom: 2px;
  position: relative;
}

.nav-item:hover {
  background: var(--bg-hover);
  color: var(--text);
}

.nav-item.active {
  background: var(--primary-bg);
  color: var(--primary);
  font-weight: 600;
}

.nav-item svg { flex-shrink: 0; }

.nav-badge {
  margin-left: auto;
  background: var(--primary);
  color: #fff;
  font-size: 11px;
  font-weight: 700;
  padding: 1px 7px;
  border-radius: 10px;
  min-width: 20px;
  text-align: center;
}

.sidebar-footer {
  padding: 12px 16px;
  border-top: 1px solid var(--border);
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 8px;
}

.data-mode {
  display: flex;
  align-items: center;
  gap: 6px;
  font-size: 12px;
  color: var(--text-muted);
}

.mode-dot {
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background: var(--warning);
}

.data-mode.online .mode-dot { background: var(--success); }
.data-mode.local .mode-dot { background: var(--info); }

.theme-toggle {
  padding: 6px;
  border-radius: var(--radius);
  color: var(--text-secondary);
  transition: all var(--transition);
}

.theme-toggle:hover { background: var(--bg-hover); color: var(--text); }

/* ==================== 主内容区 ==================== */

.main-content {
  flex: 1;
  margin-left: var(--sidebar-width);
  min-width: 0;
  display: flex;
  flex-direction: column;
}

.mobile-header {
  display: none;
  padding: 12px 16px;
  background: var(--bg-elevated);
  border-bottom: 1px solid var(--border);
  align-items: center;
  gap: 12px;
  position: sticky;
  top: 0;
  z-index: 50;
}

.menu-btn { padding: 4px; color: var(--text); }
.mobile-title { font-weight: 600; font-size: 16px; }

.page-content {
  flex: 1;
  padding: 24px 32px;
  max-width: 1200px;
  width: 100%;
  margin: 0 auto;
}

/* ==================== 加载 ==================== */

.loading-screen {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  padding: 80px 0;
  color: var(--text-muted);
  gap: 12px;
}

.spinner {
  width: 32px;
  height: 32px;
  border: 3px solid var(--border);
  border-top-color: var(--primary);
  border-radius: 50%;
  animation: spin 0.8s linear infinite;
}

@keyframes spin { to { transform: rotate(360deg); } }

/* ==================== 页面标题 ==================== */

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

.page-header-row {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: 12px;
  flex-wrap: wrap;
}

.page-header h1 {
  font-size: 24px;
  font-weight: 700;
  margin-bottom: 4px;
}

.page-header p {
  color: var(--text-secondary);
  font-size: 14px;
}

.page-header-date {
  font-size: 13px;
  color: var(--text-muted);
  padding: 6px 12px;
  background: var(--bg-hover);
  border-radius: var(--radius);
  white-space: nowrap;
  font-weight: 500;
  margin-top: 2px;
}

/* ==================== 卡片网格（仪表盘） ==================== */

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

.stat-card {
  background: var(--bg-elevated);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 20px;
  box-shadow: var(--shadow-sm);
  transition: box-shadow var(--transition);
}

.stat-card:hover { box-shadow: var(--shadow-md); }

.stat-card .stat-icon {
  width: 40px;
  height: 40px;
  border-radius: var(--radius);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 20px;
  margin-bottom: 12px;
}

.stat-card .stat-value {
  font-size: 28px;
  font-weight: 700;
  line-height: 1;
  margin-bottom: 4px;
}

.stat-card .stat-label {
  font-size: 13px;
  color: var(--text-secondary);
}

/* ==================== 通用卡片 ==================== */

.card {
  background: var(--bg-elevated);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-sm);
  overflow: hidden;
}

.card-body { padding: 20px; }

.card-title {
  font-size: 16px;
  font-weight: 600;
  margin-bottom: 16px;
}

/* ==================== 掌握程度标签 ==================== */

.mastery-badge {
  display: inline-flex;
  align-items: center;
  gap: 4px;
  padding: 2px 10px;
  border-radius: 12px;
  font-size: 12px;
  font-weight: 600;
}

.mastery-badge.m0 { background: rgba(148,163,184,0.15); color: var(--mastery-0); }
.mastery-badge.m1 { background: var(--danger-bg); color: var(--danger); }
.mastery-badge.m2 { background: var(--warning-bg); color: var(--warning); }
.mastery-badge.m3 { background: var(--info-bg); color: var(--info); }
.mastery-badge.m4 { background: var(--success-bg); color: var(--success); }

/* ==================== 按钮 ==================== */

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 8px 16px;
  border-radius: var(--radius);
  font-size: 14px;
  font-weight: 500;
  transition: all var(--transition);
  white-space: nowrap;
}

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

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

.btn-danger {
  background: var(--danger);
  color: #fff;
}
.btn-danger:hover { opacity: 0.9; }

.btn-ghost {
  color: var(--text-secondary);
  padding: 6px;
}
.btn-ghost:hover { background: var(--bg-hover); color: var(--text); }

.btn-sm { padding: 5px 10px; font-size: 13px; }
.btn-lg { padding: 12px 24px; font-size: 15px; }
.btn-block { width: 100%; }
.btn:disabled { opacity: 0.5; cursor: not-allowed; }

/* ==================== 表单 ==================== */

.form-group { margin-bottom: 16px; }

.form-label {
  display: block;
  font-size: 13px;
  font-weight: 600;
  color: var(--text-secondary);
  margin-bottom: 6px;
}

.form-input, .form-select, .form-textarea {
  width: 100%;
  padding: 10px 12px;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  font-size: 14px;
  background: var(--bg-elevated);
  color: var(--text);
  transition: border-color var(--transition), box-shadow var(--transition);
}

.form-input:focus, .form-select:focus, .form-textarea:focus {
  outline: none;
  border-color: var(--primary);
  box-shadow: 0 0 0 3px var(--primary-bg);
}

.form-textarea {
  min-height: 120px;
  resize: vertical;
  font-family: "SF Mono", "Fira Code", monospace;
  font-size: 13px;
}

.form-hint {
  font-size: 12px;
  color: var(--text-muted);
  margin-top: 4px;
}

/* ==================== 搜索栏 ==================== */

.search-bar {
  display: flex;
  gap: 8px;
  margin-bottom: 16px;
  flex-wrap: wrap;
}

.search-bar .form-input { flex: 1; min-width: 200px; }

/* ==================== 表格 ==================== */

.table-wrap {
  background: var(--bg-elevated);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  overflow: hidden;
  box-shadow: var(--shadow-sm);
}

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

th, td {
  padding: 12px 16px;
  text-align: left;
  font-size: 14px;
}

th {
  background: var(--bg-hover);
  font-weight: 600;
  color: var(--text-secondary);
  font-size: 13px;
  white-space: nowrap;
}

tbody tr {
  border-top: 1px solid var(--border-light);
  transition: background var(--transition);
}

tbody tr:hover { background: var(--bg-hover); }

.word-cell { font-weight: 600; }
.translation-cell { color: var(--text-secondary); }
.sentence-cell {
  color: var(--text-muted);
  font-size: 13px;
  max-width: 300px;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}

.actions-cell { white-space: nowrap; text-align: right; }

/* ==================== 分页 ==================== */

.pagination {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  margin-top: 16px;
}

.pagination button {
  padding: 6px 12px;
  border-radius: var(--radius);
  font-size: 13px;
  border: 1px solid var(--border);
  background: var(--bg-elevated);
  color: var(--text);
  transition: all var(--transition);
}

.pagination button:hover:not(:disabled) {
  border-color: var(--primary);
  color: var(--primary);
}

.pagination button:disabled { opacity: 0.4; cursor: not-allowed; }
.pagination .page-info { font-size: 13px; color: var(--text-secondary); padding: 0 8px; }

/* ==================== 复习界面 ==================== */

.review-container {
  min-height: calc(100vh - 100px);
  display: flex;
  flex-direction: column;
}

.review-progress {
  display: flex;
  align-items: center;
  gap: 12px;
  margin-bottom: 24px;
}

.progress-bar {
  flex: 1;
  height: 6px;
  background: var(--border);
  border-radius: 3px;
  overflow: hidden;
}

.progress-fill {
  height: 100%;
  background: var(--primary);
  border-radius: 3px;
  transition: width 0.3s ease;
}

.progress-text { font-size: 14px; color: var(--text-secondary); white-space: nowrap; }

/* 进度数字闪烁反馈 */
.progress-text.flash {
  animation: flashGreen 0.8s ease;
}

@keyframes flashGreen {
  0% { color: var(--text-secondary); }
  30% { color: var(--success); font-weight: 700; transform: scale(1.15); }
  100% { color: var(--text-secondary); transform: scale(1); }
}

/* 复习顶栏：进度 + 专注模式按钮 */
.review-topbar {
  display: flex;
  align-items: center;
  gap: 12px;
  margin-bottom: 24px;
}

.review-topbar .progress-bar { flex: 1; }

.focus-toggle {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 6px 12px;
  border-radius: var(--radius);
  border: 1px solid var(--border);
  background: var(--bg-elevated);
  color: var(--text-secondary);
  font-size: 13px;
  font-weight: 500;
  transition: all var(--transition);
  white-space: nowrap;
}

.focus-toggle:hover {
  border-color: var(--primary);
  color: var(--primary);
}

.focus-toggle.active {
  background: var(--primary-bg);
  border-color: var(--primary);
  color: var(--primary);
}

.focus-toggle svg { width: 16px; height: 16px; }

/* 卡片掌握状态指示器（右上角） */
.card-status-indicator {
  position: absolute;
  top: 16px;
  right: 16px;
  width: 48px;
  height: 4px;
  border-radius: 2px;
  transition: background var(--transition);
  z-index: 2;
}

.card-status-indicator.s-new { background: var(--mastery-0); opacity: 0.4; }
.card-status-indicator.s-learning { background: var(--mastery-1); }
.card-status-indicator.s-familiar { background: var(--mastery-2); }
.card-status-indicator.s-known { background: var(--mastery-3); }
.card-status-indicator.s-mastered { background: var(--mastery-4); }

/* ==================== 专注模式 ==================== */

.focus-mode-overlay {
  position: fixed;
  inset: 0;
  z-index: 9999;
  background: var(--bg);
  display: none;
  flex-direction: column;
  padding: 0;
  animation: fadeIn 0.3s ease;
  overflow: hidden;
}

.focus-mode-overlay.active { display: flex; }

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

.focus-mode-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 16px 20px;
  flex-shrink: 0;
  z-index: 10;
}

.focus-exit-btn {
  display: flex;
  align-items: center;
  gap: 6px;
  padding: 6px 12px;
  border-radius: var(--radius);
  background: var(--bg-elevated);
  border: 1px solid var(--border);
  color: var(--text-secondary);
  font-size: 13px;
  transition: all var(--transition);
}

.focus-exit-btn:hover { color: var(--danger); border-color: var(--danger); }

.focus-progress-text {
  font-size: 14px;
  color: var(--text-muted);
  font-weight: 500;
}

.focus-progress-text.flash {
  animation: flashGreen 0.8s ease;
}

.focus-card-wrapper {
  width: 100%;
  max-width: 600px;
  margin: 0 auto;
  flex: 1;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 8px 20px;
  min-height: 0;
}

.focus-card-wrapper .flashcard {
  height: 100%;
  max-height: 420px;
  width: 100%;
}

/* 专注模式下的评分按钮 - 正常文档流 */
.focus-mode-overlay .review-buttons {
  flex-shrink: 0;
  width: calc(100% - 32px);
  max-width: 560px;
  margin: 0 auto 8px;
}

.focus-nav-buttons {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 16px;
  flex-shrink: 0;
  padding: 8px 0 16px;
  padding-bottom: calc(8px + env(safe-area-inset-bottom, 0px));
  z-index: 10;
}

.focus-nav-btn {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 44px;
  height: 44px;
  border-radius: 50%;
  background: var(--bg-elevated);
  border: 1px solid var(--border);
  color: var(--text);
  transition: all var(--transition);
}

.focus-nav-btn:hover { border-color: var(--primary); color: var(--primary); }
.focus-nav-btn:disabled { opacity: 0.3; cursor: not-allowed; }

.focus-nav-btn svg { width: 20px; height: 20px; }

@media (max-width: 768px) {
  .focus-mode-header {
    padding: 12px 16px;
  }

  .focus-card-wrapper {
    padding: 4px 16px;
  }

  .focus-card-wrapper .flashcard {
    max-height: 360px;
  }

  .focus-mode-overlay .review-buttons {
    width: calc(100% - 24px);
    margin-bottom: 4px;
  }

  .focus-nav-buttons {
    padding: 4px 0 12px;
    padding-bottom: calc(4px + env(safe-area-inset-bottom, 0px));
  }

  .focus-nav-btn {
    width: 40px;
    height: 40px;
  }
}

/* 翻转卡片 */
.flashcard-area {
  flex: 1;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 20px 0;
}

.flashcard {
  width: 100%;
  max-width: 560px;
  height: 360px;
  perspective: 1000px;
  cursor: pointer;
}

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

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

.flashcard-front, .flashcard-back {
  position: absolute;
  width: 100%;
  height: 100%;
  backface-visibility: hidden;
  -webkit-backface-visibility: hidden;
  border-radius: var(--radius-xl);
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  padding: 32px;
  box-shadow: var(--shadow-lg);
  border: 1px solid var(--border);
}

.flashcard-front {
  background: var(--bg-elevated);
}

.flashcard-back {
  background: var(--bg-elevated);
  transform: rotateY(180deg);
}

.flashcard-word {
  font-size: 36px;
  font-weight: 700;
  margin-bottom: 8px;
  text-align: center;
}

.flashcard-pos {
  font-size: 14px;
  color: var(--text-muted);
  font-style: italic;
  margin-bottom: 16px;
}

.flashcard-ipa {
  font-size: 16px;
  color: var(--text-secondary);
  font-family: "SF Mono", "Fira Code", "Consolas", monospace;
  margin-bottom: 4px;
  text-align: center;
}

.flashcard-hint {
  font-size: 13px;
  color: var(--text-muted);
  margin-top: 24px;
}

.flashcard-translation {
  font-size: 24px;
  font-weight: 600;
  margin-bottom: 16px;
  text-align: center;
  color: var(--primary);
}

.flashcard-sentence {
  font-size: 15px;
  color: var(--text-secondary);
  text-align: center;
  line-height: 1.7;
  max-width: 420px;
  font-style: italic;
  margin-top: 8px;
}

.flashcard-front-sentence {
  font-size: 15px;
  color: var(--text-secondary);
  text-align: center;
  line-height: 1.7;
  max-width: 420px;
  font-style: italic;
  margin-top: 20px;
  padding-top: 16px;
  border-top: 1px solid var(--border-light);
  position: relative;
}

.flashcard-front-sentence::before {
  content: '例句';
  position: absolute;
  top: -8px;
  left: 50%;
  transform: translateX(-50%);
  font-size: 10px;
  font-weight: 600;
  color: var(--text-muted);
  background: var(--bg-elevated);
  padding: 0 8px;
  font-style: normal;
  letter-spacing: 1px;
}

/* 单词在例句中的高亮 */
.word-highlight {
  background: linear-gradient(transparent 55%, var(--primary-bg) 55%);
  color: var(--primary);
  font-weight: 700;
  font-style: normal;
  padding: 0 2px;
  border-radius: 2px;
}

.word-highlight-back {
  color: var(--primary);
  font-weight: 700;
  font-style: normal;
  text-decoration: underline;
  text-decoration-color: var(--primary);
  text-decoration-thickness: 2px;
  text-underline-offset: 3px;
}

.flashcard-tags {
  margin-top: 16px;
  display: flex;
  gap: 6px;
  flex-wrap: wrap;
  justify-content: center;
}

.tag {
  font-size: 12px;
  padding: 2px 8px;
  border-radius: 4px;
  background: var(--primary-bg);
  color: var(--primary);
}

/* 评分按钮 */
.review-buttons {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 8px;
  margin-top: 24px;
  max-width: 560px;
  margin-left: auto;
  margin-right: auto;
  width: 100%;
}

.review-btn {
  padding: 14px 8px;
  border-radius: var(--radius);
  font-size: 14px;
  font-weight: 600;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 2px;
  border: 1px solid var(--border);
  background: var(--bg-elevated);
  color: var(--text);
  transition: all var(--transition);
}

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

.review-btn .btn-label { font-size: 14px; }
.review-btn .btn-interval { font-size: 11px; color: var(--text-muted); }

.review-btn.again { border-color: var(--danger); }
.review-btn.again:hover { background: var(--danger-bg); }
.review-btn.hard { border-color: var(--warning); }
.review-btn.hard:hover { background: var(--warning-bg); }
.review-btn.good { border-color: var(--info); }
.review-btn.good:hover { background: var(--info-bg); }
.review-btn.easy { border-color: var(--success); }
.review-btn.easy:hover { background: var(--success-bg); }

.review-buttons.hidden { display: none; }

/* 复习完成 */
.review-complete {
  text-align: center;
  padding: 60px 20px;
}

.review-complete .complete-icon {
  font-size: 64px;
  margin-bottom: 16px;
}

.review-complete h2 {
  font-size: 24px;
  font-weight: 700;
  margin-bottom: 8px;
}

.review-complete p { color: var(--text-secondary); margin-bottom: 24px; }

/* ==================== 图表 ==================== */

.chart-container { margin-bottom: 24px; }

.bar-chart {
  display: flex;
  align-items: flex-end;
  gap: 4px;
  height: 160px;
  padding: 16px 0;
  border-bottom: 1px solid var(--border);
}

.bar-item {
  flex: 1;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 4px;
  min-width: 0;
}

.bar {
  width: 100%;
  max-width: 24px;
  background: var(--primary);
  border-radius: 3px 3px 0 0;
  min-height: 2px;
  transition: height 0.3s ease;
  position: relative;
}

.bar:hover { background: var(--primary-light); }

.bar-tooltip {
  position: absolute;
  top: -20px;
  left: 50%;
  transform: translateX(-50%);
  font-size: 11px;
  color: var(--text-secondary);
  white-space: nowrap;
}

.bar-label {
  font-size: 10px;
  color: var(--text-muted);
  white-space: nowrap;
  overflow: hidden;
}

/* 掌握程度分布 */
.mastery-bars {
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.mastery-bar-row {
  display: flex;
  align-items: center;
  gap: 12px;
}

.mastery-bar-label {
  width: 60px;
  font-size: 13px;
  font-weight: 500;
  flex-shrink: 0;
}

.mastery-bar-track {
  flex: 1;
  height: 24px;
  background: var(--bg-hover);
  border-radius: 4px;
  overflow: hidden;
}

.mastery-bar-fill {
  height: 100%;
  border-radius: 4px;
  transition: width 0.4s ease;
  display: flex;
  align-items: center;
  justify-content: flex-end;
  padding-right: 8px;
  font-size: 12px;
  font-weight: 600;
  color: #fff;
  min-width: 28px;
}

.mastery-bar-fill.m0 { background: var(--mastery-0); }
.mastery-bar-fill.m1 { background: var(--mastery-1); }
.mastery-bar-fill.m2 { background: var(--mastery-2); }
.mastery-bar-fill.m3 { background: var(--mastery-3); }
.mastery-bar-fill.m4 { background: var(--mastery-4); }

/* ==================== Toast ==================== */

.toast-container {
  position: fixed;
  top: 20px;
  right: 20px;
  z-index: 9999;
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.toast {
  padding: 12px 16px;
  border-radius: var(--radius);
  font-size: 14px;
  font-weight: 500;
  box-shadow: var(--shadow-lg);
  animation: toastIn 0.3s ease;
  max-width: 360px;
  display: flex;
  align-items: center;
  gap: 8px;
}

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

@keyframes toastIn {
  from { transform: translateX(120%); opacity: 0; }
  to { transform: translateX(0); opacity: 1; }
}

/* ==================== 空状态 ==================== */

.empty-state {
  text-align: center;
  padding: 60px 20px;
  color: var(--text-muted);
}

.empty-state .empty-icon {
  font-size: 48px;
  margin-bottom: 12px;
  opacity: 0.5;
}

.empty-state h3 {
  font-size: 16px;
  font-weight: 600;
  color: var(--text-secondary);
  margin-bottom: 4px;
}

.empty-state p { font-size: 14px; margin-bottom: 16px; }

/* ==================== 工具类 ==================== */

.flex { display: flex; }
.items-center { align-items: center; }
.justify-between { justify-content: space-between; }
.gap-2 { gap: 8px; }
.gap-3 { gap: 12px; }
.mt-4 { margin-top: 16px; }
.mb-4 { margin-bottom: 16px; }
.text-sm { font-size: 13px; }
.text-muted { color: var(--text-muted); }
.text-center { text-align: center; }
.hidden { display: none !important; }

/* ==================== 响应式 ==================== */

.sidebar-overlay {
  display: none;
  position: fixed;
  inset: 0;
  background: rgba(0,0,0,0.3);
  z-index: 99;
}

/* ==================== 移动端底部导航栏 ==================== */

.mobile-tabbar {
  display: none;
  position: fixed;
  bottom: 0;
  left: 0;
  right: 0;
  background: var(--bg-elevated);
  border-top: 1px solid var(--border);
  z-index: 100;
  padding: 0;
  padding-bottom: env(safe-area-inset-bottom, 0);
  box-shadow: 0 -2px 10px rgba(0,0,0,0.04);
}

.mobile-tabbar-inner {
  display: flex;
  height: 56px;
}

.tabbar-item {
  flex: 1;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 2px;
  color: var(--text-muted);
  font-size: 11px;
  font-weight: 500;
  transition: color var(--transition);
  position: relative;
}

.tabbar-item svg { width: 22px; height: 22px; }

.tabbar-item.active {
  color: var(--primary);
  font-weight: 600;
}

.tabbar-item.active::before {
  content: '';
  position: absolute;
  top: 0;
  left: 50%;
  transform: translateX(-50%);
  width: 32px;
  height: 3px;
  background: var(--primary);
  border-radius: 0 0 3px 3px;
}

.tabbar-badge {
  position: absolute;
  top: 6px;
  right: calc(50% - 24px);
  background: var(--primary);
  color: #fff;
  font-size: 10px;
  font-weight: 700;
  padding: 0 5px;
  border-radius: 10px;
  min-width: 16px;
  height: 16px;
  line-height: 16px;
  text-align: center;
}

@media (max-width: 768px) {
  .sidebar {
    transform: translateX(-100%);
  }

  .sidebar.open {
    transform: translateX(0);
  }

  .sidebar-overlay.show {
    display: block;
  }

  /* 移动端隐藏桌面专属功能 */
  .nav-item.desktop-only {
    display: none;
  }

  /* 显示底部导航栏 */
  .mobile-tabbar {
    display: block;
  }

  .main-content {
    margin-left: 0;
  }

  .mobile-header {
    display: flex;
  }

  .page-content {
    padding: 16px;
    padding-bottom: 80px;
  }

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

  .dashboard-charts,
  .stats-charts {
    grid-template-columns: 1fr !important;
  }

  .review-buttons {
    grid-template-columns: repeat(2, 1fr);
    gap: 8px;
    margin-bottom: 16px;
  }

  .flashcard {
    height: 320px;
  }

  .flashcard-word {
    font-size: 26px;
  }

  .flashcard-translation {
    font-size: 20px;
  }

  .flashcard-sentence,
  .flashcard-front-sentence {
    font-size: 14px;
  }

  th, td {
    padding: 8px 10px;
    font-size: 13px;
  }

  .sentence-cell { display: none; }

  .review-container {
    min-height: calc(100vh - 180px);
  }

  .flashcard-area {
    padding: 8px 0;
  }
}

@media (max-width: 480px) {
  .stats-grid {
    grid-template-columns: 1fr;
  }

  .flashcard {
    height: 300px;
  }

  .flashcard-word {
    font-size: 24px;
  }
}

/* ==================== CSV 导入预览 ==================== */

.csv-format-guide {
  display: flex;
  gap: 16px;
  flex-wrap: wrap;
}

.csv-format-block {
  flex: 1;
  min-width: 280px;
}

.csv-format-title {
  font-size: 12px;
  font-weight: 600;
  color: var(--text-secondary);
  margin-bottom: 6px;
}

.csv-format-code {
  background: var(--bg-hover);
  border-radius: var(--radius);
  padding: 10px 12px;
  font-size: 12px;
  color: var(--text-secondary);
  font-family: "SF Mono", "Fira Code", monospace;
  overflow-x: auto;
  white-space: pre;
  line-height: 1.5;
}

.import-preview-header {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: 12px;
  margin-bottom: 16px;
  flex-wrap: wrap;
}

.import-preview-toolbar {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 8px 0;
  border-bottom: 1px solid var(--border-light);
  margin-bottom: 8px;
}

.import-checkbox-all {
  display: flex;
  align-items: center;
  gap: 6px;
  font-size: 13px;
  font-weight: 500;
  cursor: pointer;
}

.import-checkbox-all input {
  width: 16px;
  height: 16px;
  cursor: pointer;
}

.import-selected-count {
  font-size: 12px;
  color: var(--text-muted);
}

.import-table-wrap {
  overflow-x: auto;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  max-height: 500px;
  overflow-y: auto;
}

.import-preview-table {
  width: 100%;
  border-collapse: collapse;
  font-size: 13px;
}

.import-preview-table th {
  background: var(--bg-hover);
  font-weight: 600;
  color: var(--text-secondary);
  font-size: 12px;
  padding: 8px 10px;
  text-align: left;
  position: sticky;
  top: 0;
  z-index: 1;
  border-bottom: 1px solid var(--border);
}

.import-preview-table td {
  padding: 6px 8px;
  border-bottom: 1px solid var(--border-light);
  vertical-align: middle;
}

.import-preview-table tr.row-needs-review {
  background: var(--warning-bg);
}

.import-preview-table tr.row-needs-review:hover {
  background: rgba(245, 158, 11, 0.15);
}

.import-row-check {
  width: 16px;
  height: 16px;
  cursor: pointer;
}

.import-edit {
  border: 1px solid transparent;
  border-radius: 4px;
  padding: 4px 6px;
  font-size: 13px;
  background: transparent;
  color: var(--text);
  transition: border-color var(--transition), background var(--transition);
}

.import-edit:hover {
  border-color: var(--border);
  background: var(--bg-elevated);
}

.import-edit:focus {
  outline: none;
  border-color: var(--primary);
  background: var(--bg-elevated);
  box-shadow: 0 0 0 2px var(--primary-bg);
}

.import-status {
  display: inline-flex;
  align-items: center;
  padding: 2px 8px;
  border-radius: 10px;
  font-size: 11px;
  font-weight: 600;
  white-space: nowrap;
}

.import-status-ok {
  background: var(--success-bg);
  color: var(--success);
}

.import-status-review {
  background: var(--warning-bg);
  color: var(--warning);
  cursor: help;
}

.import-issues-legend {
  margin-top: 16px;
  padding: 12px;
  background: var(--warning-bg);
  border-radius: var(--radius);
}

.import-issues-title {
  font-size: 12px;
  font-weight: 600;
  color: var(--warning);
  margin-bottom: 8px;
}

.import-issues-list {
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
}

.import-issue-tag {
  display: inline-block;
  padding: 2px 8px;
  background: var(--bg-elevated);
  border: 1px solid var(--border);
  border-radius: 10px;
  font-size: 11px;
  color: var(--text-secondary);
}