/* ========== 全局重置 & 变量 ========== */
:root {
  --color-primary: #4A90D9;
  --color-primary-dark: #3A7BC8;
  --color-primary-light: #E8F1FC;
  --color-success: #52C41A;
  --color-success-light: #F0FBE8;
  --color-danger: #FF4D4F;
  --color-danger-light: #FFF1F0;
  --color-warning: #FAAD14;
  --color-warning-light: #FFFBE6;
  --color-info: #1890FF;
  --color-info-light: #E6F7FF;
  --color-bg: #F5F7FA;
  --color-card-bg: #FFFFFF;
  --color-text: #1A1A2E;
  --color-text-secondary: #6B7280;
  --color-text-tertiary: #9CA3AF;
  --color-border: #E5E7EB;
  --color-border-light: #F3F4F6;
  --color-shadow: rgba(0, 0, 0, 0.06);
  --color-shadow-hover: rgba(0, 0, 0, 0.12);
  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 16px;
  --transition: 0.25s ease;
}

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

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", "Helvetica Neue", Helvetica, Arial, sans-serif;
  background: var(--color-bg);
  color: var(--color-text);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
  -webkit-tap-highlight-color: transparent;
  -webkit-touch-callout: none;
  overscroll-behavior-y: none;
  overflow-x: hidden;
}

img { -webkit-touch-callout: default; }

/* ========== 布局 ========== */
.app-container {
  max-width: 900px;
  margin: 0 auto;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

.app-header {
  background: var(--color-card-bg);
  border-bottom: 1px solid var(--color-border);
  padding: 14px 20px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  position: sticky;
  top: 0;
  z-index: 100;
  box-shadow: 0 1px 4px var(--color-shadow);
}

.app-header h1 {
  font-size: 18px;
  font-weight: 700;
  color: var(--color-primary);
  display: flex;
  align-items: center;
  gap: 8px;
}

.app-header .header-subtitle {
  font-size: 12px;
  color: var(--color-text-tertiary);
}

/* 导航栏 */
.nav-bar {
  background: var(--color-card-bg);
  border-bottom: 1px solid var(--color-border);
  display: flex;
  justify-content: space-around;
  padding: 0;
  position: sticky;
  top: 52px;
  z-index: 99;
}

.nav-item {
  flex: 1;
  padding: 12px 8px;
  text-align: center;
  cursor: pointer;
  color: var(--color-text-secondary);
  font-size: 13px;
  font-weight: 500;
  transition: var(--transition);
  border-bottom: 3px solid transparent;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 2px;
  text-decoration: none;
}

.nav-item:hover {
  color: var(--color-primary);
  background: var(--color-primary-light);
}

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

.nav-icon {
  font-size: 20px;
}

/* 主内容区 */
#main-content {
  flex: 1;
  padding: 20px;
  max-width: 900px;
  width: 100%;
  margin: 0 auto;
  overflow-y: auto;
}

/* ========== 按钮 ========== */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 6px;
  padding: 8px 18px;
  border: none;
  border-radius: var(--radius-sm);
  font-size: 14px;
  font-weight: 500;
  cursor: pointer;
  transition: var(--transition);
  text-decoration: none;
  white-space: nowrap;
}

.btn:hover {
  transform: translateY(-1px);
  box-shadow: 0 4px 12px var(--color-shadow-hover);
}

.btn:active {
  transform: translateY(0);
}

.btn-primary { background: var(--color-primary); color: white; }
.btn-primary:hover { background: var(--color-primary-dark); }
.btn-success { background: var(--color-success); color: white; }
.btn-danger { background: var(--color-danger); color: white; }
.btn-warning { background: var(--color-warning); color: white; }
.btn-info { background: var(--color-info); color: white; }
.btn-secondary { background: var(--color-border); color: var(--color-text-secondary); }

.btn-sm { padding: 5px 12px; font-size: 12px; }
.btn-lg, .btn-large { padding: 12px 28px; font-size: 16px; }
.btn-block { width: 100%; }

/* ========== 首页 ========== */
.dashboard-header { margin-bottom: 20px; }

.welcome-banner {
  background: linear-gradient(135deg, #4A90D9 0%, #5BA0E9 100%);
  color: white;
  border-radius: var(--radius-lg);
  padding: 30px;
  display: flex;
  gap: 20px;
  align-items: flex-start;
}

.welcome-icon { font-size: 48px; }
.welcome-text h2 { font-size: 22px; margin-bottom: 8px; }
.welcome-text p { opacity: 0.9; margin-bottom: 4px; font-size: 14px; }
.welcome-hint { margin-top: 8px !important; font-size: 13px !important; opacity: 0.8; }

.day-banner {
  background: linear-gradient(135deg, #4A90D9 0%, #5BA0E9 100%);
  color: white;
  border-radius: var(--radius-lg);
  padding: 24px 30px;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.day-number {
  font-size: 32px;
  font-weight: 800;
  letter-spacing: 1px;
}

.day-info { text-align: right; }
.day-streak { font-size: 18px; font-weight: 600; }
.day-date { font-size: 13px; opacity: 0.8; margin-top: 4px; }

/* 区块 */
.section {
  background: var(--color-card-bg);
  border-radius: var(--radius-md);
  padding: 20px;
  margin-bottom: 16px;
  box-shadow: 0 1px 3px var(--color-shadow);
}

.section-title {
  font-size: 16px;
  font-weight: 600;
  margin-bottom: 16px;
  color: var(--color-text);
}

/* 任务卡片 */
.task-cards {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 12px;
  margin-bottom: 16px;
}

.task-card {
  border-radius: var(--radius-md);
  padding: 16px;
  text-align: center;
  transition: var(--transition);
}

.task-card:hover { transform: translateY(-2px); box-shadow: 0 4px 16px var(--color-shadow-hover); }

.task-new { background: var(--color-info-light); border: 1px solid #B3DBFF; }
.task-review { background: var(--color-warning-light); border: 1px solid #FFE58F; }
.task-total { background: var(--color-success-light); border: 1px solid #B7EB8F; }

.task-card-icon { font-size: 28px; margin-bottom: 8px; }
.task-card-label { font-size: 13px; color: var(--color-text-secondary); margin-bottom: 4px; }
.task-card-count { font-size: 28px; font-weight: 700; color: var(--color-text); }
.task-card-count span { font-size: 14px; font-weight: 400; margin-left: 2px; }
.task-card-time { font-size: 12px; color: var(--color-text-tertiary); margin-top: 4px; }

/* 操作区 */
.dashboard-actions {
  text-align: center;
  padding: 10px 0;
}

/* 空状态 */
.empty-state {
  text-align: center;
  padding: 30px 20px;
}

.empty-icon { font-size: 48px; margin-bottom: 12px; }
.empty-state p { font-size: 16px; color: var(--color-text-secondary); margin-bottom: 4px; }
.empty-sub { font-size: 13px !important; color: var(--color-text-tertiary) !important; }

/* 计时器 */
.timer-display {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 20px;
  padding: 20px;
}

.timer-time {
  font-size: 42px;
  font-weight: 700;
  font-variant-numeric: tabular-nums;
  color: var(--color-primary);
  letter-spacing: 2px;
}

.timer-controls { display: flex; gap: 8px; }

/* 进度条 */
.progress-bar-container { margin-bottom: 16px; }
.progress-bar-labels {
  display: flex;
  justify-content: space-between;
  margin-bottom: 6px;
  font-size: 13px;
  color: var(--color-text-secondary);
}

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

.progress-bar-fill {
  height: 100%;
  background: var(--color-primary);
  border-radius: 5px;
  transition: width 0.5s ease;
}

.progress-bar-fill.progress-mastered { background: var(--color-success); }

/* 统计行 */
.stats-row {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 12px;
  margin-top: 16px;
}

.stat-item {
  text-align: center;
  padding: 12px;
  background: var(--color-bg);
  border-radius: var(--radius-sm);
}

.stat-num {
  display: block;
  font-size: 20px;
  font-weight: 700;
  color: var(--color-text);
}

.stat-label {
  font-size: 12px;
  color: var(--color-text-tertiary);
}

/* 未来复习预览 */
.upcoming-chart {
  display: flex;
  align-items: flex-end;
  gap: 8px;
  height: 120px;
  padding: 10px 0;
}

.upcoming-bar-wrapper {
  flex: 1;
  display: flex;
  flex-direction: column;
  align-items: center;
  height: 100%;
  justify-content: flex-end;
}

.upcoming-bar-count {
  font-size: 12px;
  font-weight: 600;
  color: var(--color-text-secondary);
  margin-bottom: 4px;
}

.upcoming-bar {
  width: 70%;
  background: var(--color-primary-light);
  border-radius: 4px 4px 0 0;
  min-height: 8px;
  display: flex;
  align-items: flex-end;
  transition: var(--transition);
}

.upcoming-bar.today { background: var(--color-primary); }

.upcoming-bar-inner {
  width: 100%;
  height: 100%;
  background: var(--color-primary);
  border-radius: 4px 4px 0 0;
  opacity: 0.7;
}

.upcoming-bar.today .upcoming-bar-inner { opacity: 1; }

.upcoming-bar-label {
  font-size: 11px;
  color: var(--color-text-tertiary);
  margin-top: 6px;
}

/* ========== 背诵学习页 ========== */
.study-container {
  max-width: 700px;
  margin: 0 auto;
}

.study-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 12px;
}

.study-progress-info {
  display: flex;
  align-items: center;
  gap: 10px;
}

.study-counter {
  font-size: 16px;
  font-weight: 700;
  color: var(--color-text);
}

.study-type-badge {
  font-size: 12px;
  padding: 3px 10px;
  border-radius: 12px;
  font-weight: 500;
}

.badge-new { background: var(--color-info-light); color: var(--color-info); }
.badge-review { background: var(--color-warning-light); color: var(--color-warning); }

.study-timer {
  font-size: 20px;
  font-weight: 700;
  font-variant-numeric: tabular-nums;
  color: var(--color-primary);
  background: var(--color-primary-light);
  padding: 6px 14px;
  border-radius: var(--radius-sm);
}

.study-progress-bar {
  height: 6px;
  background: var(--color-border-light);
  border-radius: 3px;
  margin-bottom: 20px;
  overflow: hidden;
}

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

/* 闪卡 */
.flashcard {
  background: var(--color-card-bg);
  border-radius: var(--radius-lg);
  padding: 28px;
  box-shadow: 0 2px 12px var(--color-shadow);
}

.flashcard-chapter {
  font-size: 12px;
  color: var(--color-text-tertiary);
  margin-bottom: 16px;
  padding-bottom: 12px;
  border-bottom: 1px solid var(--color-border-light);
}

.flashcard-question, .flashcard-answer {
  margin-bottom: 20px;
}

.flashcard-label {
  font-size: 13px;
  font-weight: 600;
  color: var(--color-primary);
  margin-bottom: 8px;
  display: flex;
  align-items: center;
  gap: 4px;
}

.flashcard-content {
  font-size: 15px;
  line-height: 1.8;
  color: var(--color-text);
}

.flashcard-answer {
  background: var(--color-success-light);
  padding: 16px;
  border-radius: var(--radius-sm);
  border-left: 3px solid var(--color-success);
}

.flashcard-answer .flashcard-label { color: var(--color-success); }

.flashcard-hint {
  background: var(--color-warning-light);
  padding: 12px 16px;
  border-radius: var(--radius-sm);
  font-size: 13px;
  color: var(--color-text-secondary);
  display: flex;
  gap: 8px;
  align-items: flex-start;
  margin-bottom: 20px;
}

.flashcard-think {
  text-align: center;
  padding: 30px 20px;
  color: var(--color-text-tertiary);
  font-size: 14px;
}

.flashcard-actions {
  display: flex;
  gap: 12px;
  margin-top: 20px;
}

.difficulty-stars {
  color: var(--color-warning);
  font-size: 14px;
  letter-spacing: 2px;
}

.difficulty-stars.small { font-size: 12px; }

/* 复习历史 */
.review-history {
  margin-top: 20px;
  padding: 14px;
  background: var(--color-bg);
  border-radius: var(--radius-sm);
}

.review-history-title {
  font-size: 13px;
  font-weight: 600;
  color: var(--color-text-secondary);
  margin-bottom: 8px;
}

.review-history-items {
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
}

.review-history-tag {
  font-size: 11px;
  padding: 2px 8px;
  background: var(--color-card-bg);
  border: 1px solid var(--color-border);
  border-radius: 10px;
  color: var(--color-text-secondary);
}

.study-footer {
  text-align: center;
  margin-top: 20px;
}

/* 完成页 */
.study-complete, .checkin-success {
  text-align: center;
  padding: 40px 20px;
}

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

.study-complete h2, .checkin-success h2 {
  font-size: 24px;
  margin-bottom: 8px;
  color: var(--color-text);
}

.checkin-date {
  color: var(--color-text-tertiary);
  font-size: 14px;
  margin-bottom: 24px;
}

.complete-stats, .checkin-stats {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 12px;
  margin: 24px 0;
}

.complete-stat, .checkin-stat {
  background: var(--color-card-bg);
  padding: 16px;
  border-radius: var(--radius-md);
  box-shadow: 0 1px 3px var(--color-shadow);
}

.complete-stat-num, .checkin-stat-num {
  font-size: 24px;
  font-weight: 700;
  color: var(--color-primary);
  margin-bottom: 4px;
}

.complete-stat-label, .checkin-stat-label {
  font-size: 12px;
  color: var(--color-text-secondary);
}

.complete-hint {
  background: var(--color-warning-light);
  padding: 14px;
  border-radius: var(--radius-sm);
  font-size: 13px;
  color: var(--color-text-secondary);
  margin: 16px 0;
  text-align: left;
}

.complete-actions, .checkin-actions {
  display: flex;
  gap: 12px;
  justify-content: center;
  margin-top: 24px;
}

/* ========== 日历页 ========== */
.calendar-page { max-width: 800px; margin: 0 auto; }

.calendar-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 16px;
  flex-wrap: wrap;
  gap: 8px;
}

.calendar-header h2 { font-size: 20px; }

.calendar-month-stats {
  display: flex;
  gap: 16px;
  font-size: 13px;
  color: var(--color-text-secondary);
}

.cal-stat strong { color: var(--color-primary); font-size: 15px; }

.calendar-nav {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 16px;
}

.calendar-current-month {
  font-size: 16px;
  font-weight: 600;
}

.calendar-grid {
  display: grid;
  grid-template-columns: repeat(7, 1fr);
  gap: 4px;
  background: var(--color-card-bg);
  padding: 12px;
  border-radius: var(--radius-md);
  box-shadow: 0 1px 3px var(--color-shadow);
}

.calendar-weekday {
  text-align: center;
  font-size: 12px;
  font-weight: 600;
  color: var(--color-text-tertiary);
  padding: 8px 0;
}

.calendar-day {
  aspect-ratio: 1;
  border-radius: var(--radius-sm);
  padding: 4px;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  transition: var(--transition);
  position: relative;
  min-height: 60px;
}

.calendar-day:hover { transform: scale(1.05); }
.calendar-day.empty { cursor: default; }
.calendar-day.empty:hover { transform: none; }

.calendar-day .cal-day-num { font-size: 13px; font-weight: 600; }
.calendar-day .cal-day-check { font-size: 16px; margin: 2px 0; }
.calendar-day .cal-day-detail { font-size: 9px; color: var(--color-text-tertiary); }

.calendar-day.completed {
  background: var(--color-success-light);
  border: 1px solid var(--color-success);
}

.calendar-day.incomplete {
  background: var(--color-warning-light);
  border: 1px solid var(--color-warning);
}

.calendar-day.start-day {
  background: var(--color-info-light);
  border: 2px solid var(--color-info);
}

.calendar-day.today {
  box-shadow: 0 0 0 2px var(--color-primary);
}

.calendar-day.future {
  opacity: 0.4;
}

.calendar-day.before-start {
  opacity: 0.3;
}

.calendar-legend {
  display: flex;
  gap: 16px;
  margin-top: 16px;
  flex-wrap: wrap;
  justify-content: center;
}

.legend-item {
  display: flex;
  align-items: center;
  gap: 6px;
  font-size: 13px;
  color: var(--color-text-secondary);
}

.legend-dot {
  width: 14px;
  height: 14px;
  border-radius: 3px;
}

.legend-completed { background: var(--color-success-light); border: 1px solid var(--color-success); }
.legend-incomplete { background: var(--color-warning-light); border: 1px solid var(--color-warning); }
.legend-start { background: var(--color-info-light); border: 1px solid var(--color-info); }
.legend-today { background: transparent; border: 2px solid var(--color-primary); }

/* ========== 题库页 ========== */
.library-page { max-width: 800px; margin: 0 auto; }
.library-page h2 { font-size: 20px; margin-bottom: 20px; }

/* 章节筛选标签栏 */
.chapter-filter {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-bottom: 20px;
}

.filter-tab {
  padding: 6px 16px;
  border-radius: 18px;
  border: 1px solid var(--color-border);
  background: var(--color-card-bg);
  color: var(--color-text-secondary);
  font-size: 13px;
  cursor: pointer;
  transition: var(--transition);
}

.filter-tab:hover {
  border-color: var(--color-primary);
  color: var(--color-primary);
}

.filter-tab.active {
  background: var(--color-primary);
  border-color: var(--color-primary);
  color: #fff;
  font-weight: 600;
}

.library-chapter {
  background: var(--color-card-bg);
  border-radius: var(--radius-md);
  margin-bottom: 16px;
  box-shadow: 0 1px 3px var(--color-shadow);
  overflow: hidden;
}

.chapter-header {
  padding: 16px 20px;
  display: flex;
  justify-content: space-between;
  align-items: center;
  cursor: pointer;
  transition: var(--transition);
}

.chapter-header:hover { background: var(--color-bg); }

.chapter-header h3 { font-size: 15px; font-weight: 600; }

.chapter-stats {
  display: flex;
  align-items: center;
  gap: 12px;
  font-size: 12px;
}

.chapter-progress {
  background: var(--color-primary-light);
  color: var(--color-primary);
  padding: 2px 8px;
  border-radius: 10px;
  font-weight: 600;
}

.chapter-mastered { color: var(--color-success); }
.chapter-toggle { color: var(--color-text-tertiary); }

.chapter-badge {
  font-size: 11px;
  padding: 2px 8px;
  border-radius: 10px;
}

.chapter-pending { background: var(--color-border); color: var(--color-text-tertiary); }

.chapter-empty {
  padding: 20px;
  color: var(--color-text-tertiary);
  font-size: 13px;
  text-align: center;
}

.chapter-items { padding: 0 8px 8px; }

.library-item {
  display: flex;
  gap: 12px;
  padding: 12px;
  border-radius: var(--radius-sm);
  cursor: pointer;
  transition: var(--transition);
  margin: 4px 0;
}

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

.item-num {
  width: 28px;
  height: 28px;
  border-radius: 50%;
  background: var(--color-border-light);
  color: var(--color-text-secondary);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 12px;
  font-weight: 600;
  flex-shrink: 0;
}

.item-mastered .item-num { background: var(--color-success-light); color: var(--color-success); }
.item-reviewing .item-num { background: var(--color-warning-light); color: var(--color-warning); }
.item-learning .item-num { background: var(--color-info-light); color: var(--color-info); }

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

.item-question {
  font-size: 14px;
  color: var(--color-text);
  margin-bottom: 4px;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}

.item-meta {
  display: flex;
  align-items: center;
  gap: 8px;
  flex-wrap: wrap;
}

.item-status {
  font-size: 11px;
  padding: 1px 6px;
  border-radius: 8px;
  font-weight: 500;
}

.status-new { background: var(--color-border); color: var(--color-text-tertiary); }
.status-mastered { background: var(--color-success-light); color: var(--color-success); }
.status-reviewing { background: var(--color-warning-light); color: var(--color-warning); }
.status-learning { background: var(--color-info-light); color: var(--color-info); }

.item-next-review { font-size: 11px; color: var(--color-text-tertiary); }

/* 题目详情 */
.item-detail-page { max-width: 700px; margin: 0 auto; }

.item-detail-card {
  background: var(--color-card-bg);
  border-radius: var(--radius-lg);
  padding: 24px;
  box-shadow: 0 2px 8px var(--color-shadow);
}

.item-detail-chapter {
  font-size: 12px;
  color: var(--color-text-tertiary);
  margin-bottom: 12px;
}

.item-detail-section { margin-bottom: 20px; }

.item-detail-label {
  font-size: 13px;
  font-weight: 600;
  color: var(--color-primary);
  margin-bottom: 8px;
}

.item-detail-content {
  font-size: 15px;
  line-height: 1.8;
  color: var(--color-text);
}

.item-detail-hint {
  background: var(--color-warning-light);
  padding: 12px 16px;
  border-radius: var(--radius-sm);
  font-size: 13px;
  display: flex;
  gap: 8px;
  margin-bottom: 20px;
  color: var(--color-text-secondary);
}

.item-detail-status {
  background: var(--color-bg);
  padding: 16px;
  border-radius: var(--radius-sm);
  margin-bottom: 16px;
}

.detail-status-row {
  display: flex;
  justify-content: space-between;
  padding: 4px 0;
  font-size: 13px;
}

.detail-status-row span { color: var(--color-text-secondary); }

.item-detail-history {
  background: var(--color-bg);
  padding: 16px;
  border-radius: var(--radius-sm);
}

.history-title {
  font-size: 13px;
  font-weight: 600;
  margin-bottom: 8px;
  color: var(--color-text-secondary);
}

.history-item {
  display: flex;
  justify-content: space-between;
  padding: 4px 0;
  font-size: 13px;
  border-bottom: 1px solid var(--color-border-light);
}

/* ========== 统计页 ========== */
.stats-page { max-width: 800px; margin: 0 auto; }
.stats-page h2 { font-size: 20px; margin-bottom: 20px; }

.stats-overview {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 12px;
  margin-bottom: 24px;
}

.stat-card {
  background: var(--color-card-bg);
  border-radius: var(--radius-md);
  padding: 16px;
  text-align: center;
  box-shadow: 0 1px 3px var(--color-shadow);
}

.stat-card-icon { font-size: 24px; margin-bottom: 8px; }
.stat-card-value { font-size: 22px; font-weight: 700; color: var(--color-primary); margin-bottom: 4px; }
.stat-card-label { font-size: 12px; color: var(--color-text-secondary); }

.stats-section {
  background: var(--color-card-bg);
  border-radius: var(--radius-md);
  padding: 20px;
  margin-bottom: 16px;
  box-shadow: 0 1px 3px var(--color-shadow);
}

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

/* 章节统计 */
.chapter-stat-item {
  display: grid;
  grid-template-columns: 1fr 2fr auto;
  gap: 12px;
  align-items: center;
  margin-bottom: 12px;
}

.chapter-stat-name { font-size: 13px; color: var(--color-text); }

.chapter-stat-bar {
  height: 12px;
  background: var(--color-border-light);
  border-radius: 6px;
  overflow: hidden;
  position: relative;
}

.chapter-stat-fill {
  height: 100%;
  background: var(--color-primary);
  border-radius: 6px;
  opacity: 0.3;
  position: absolute;
  top: 0;
  left: 0;
  transition: width 0.5s ease;
}

.chapter-stat-fill.mastered {
  background: var(--color-success);
  opacity: 1;
}

.chapter-stat-num {
  font-size: 12px;
  color: var(--color-text-secondary);
  font-weight: 600;
  white-space: nowrap;
}

/* 热力图 */
.heatmap {
  display: grid;
  grid-template-columns: repeat(14, 1fr);
  gap: 4px;
}

.heatmap-cell {
  aspect-ratio: 1;
  border-radius: 4px;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  font-size: 10px;
  min-height: 40px;
}

.heatmap-day { font-weight: 600; font-size: 11px; }
.heatmap-label { font-size: 8px; opacity: 0.7; }

.heat-0 { background: var(--color-border-light); color: var(--color-text-tertiary); }
.heat-1 { background: #C6E5B5; color: #2D5A1E; }
.heat-2 { background: #8BC97A; color: #1E3F12; }
.heat-3 { background: #52A93F; color: white; }
.heat-4 { background: #2E7D1A; color: white; }

/* 设置 */
.settings-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 12px;
  margin-bottom: 16px;
}

.setting-item {
  display: flex;
  flex-direction: column;
  gap: 6px;
}

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

.setting-item input {
  padding: 8px 12px;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-sm);
  font-size: 14px;
  color: var(--color-text);
}

.setting-item input:focus {
  outline: none;
  border-color: var(--color-primary);
  box-shadow: 0 0 0 2px var(--color-primary-light);
}

/* 每日不限题量开关 */
.switch-label {
  display: flex;
  flex-direction: row;
  align-items: center;
  gap: 10px;
  cursor: pointer;
  user-select: none;
}
.switch-label input[type="checkbox"] {
  width: 18px;
  height: 18px;
  margin: 0;
  padding: 0;
  accent-color: var(--color-primary);
  cursor: pointer;
  flex: none;
}
.switch-text {
  font-size: 13px;
  color: var(--color-text-secondary);
  line-height: 1.4;
}

.settings-actions {
  display: flex;
  gap: 12px;
  padding-top: 12px;
  border-top: 1px solid var(--color-border-light);
}

/* ========== 响应式：手机端（≤768px） ========== */
@media (max-width: 768px) {
  /* ---------- 顶部标题栏 ---------- */
  .app-header {
    padding: 10px 16px;
    justify-content: center;
    text-align: center;
  }
  .app-header h1 { font-size: 16px; }
  .app-header .header-subtitle { display: none; }

  /* ---------- 底部固定导航（小程序 tabBar 风格） ---------- */
  .nav-bar {
    position: fixed;
    top: auto;
    bottom: 0;
    left: 0;
    right: 0;
    background: rgba(255, 255, 255, 0.96);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    border-top: 1px solid var(--color-border);
    border-bottom: none;
    box-shadow: 0 -2px 12px rgba(0, 0, 0, 0.06);
    padding-bottom: env(safe-area-inset-bottom);
    z-index: 200;
  }

  .nav-item {
    padding: 7px 4px 9px;
    font-size: 11px;
    border-bottom: none;
    gap: 2px;
    -webkit-tap-highlight-color: transparent;
  }
  .nav-item:hover { background: none; }
  .nav-item:active { background: var(--color-primary-light); }
  .nav-item.active {
    border-bottom: none;
    position: relative;
  }
  .nav-item.active::before {
    content: '';
    position: absolute;
    top: 0;
    left: 50%;
    transform: translateX(-50%);
    width: 24px;
    height: 3px;
    border-radius: 0 0 3px 3px;
    background: var(--color-primary);
  }
  .nav-icon { font-size: 22px; }

  /* ---------- 主内容区（底部为导航留白） ---------- */
  #main-content {
    padding: 12px 12px calc(76px + env(safe-area-inset-bottom));
    overflow-y: visible;
  }

  /* ---------- 全局触摸反馈 ---------- */
  .btn { min-height: 40px; }
  .btn:active { transform: scale(0.97); }
  .btn:hover { transform: none; box-shadow: none; }
  .btn-lg, .btn-large { min-height: 48px; font-size: 16px; }
  .btn-sm { min-height: 34px; }
  .library-item, .chapter-header, .calendar-day { -webkit-tap-highlight-color: rgba(74, 144, 217, 0.15); }
  .library-item:hover, .chapter-header:hover, .task-card:hover, .calendar-day:hover { transform: none; box-shadow: none; }
  .library-item:active, .chapter-header:active { background: var(--color-bg); }
  .task-card:active { box-shadow: 0 4px 16px var(--color-shadow-hover); }
  .calendar-day:active { transform: scale(0.95); }

  /* 输入框 16px 防 iOS 聚焦自动缩放 */
  .setting-item input, .cloudsync-input { font-size: 16px; }

  /* ---------- 首页 ---------- */
  .welcome-banner, .day-banner { padding: 18px 16px; flex-direction: column; gap: 10px; }
  .day-number { font-size: 26px; }
  .day-streak { font-size: 16px; }
  .welcome-icon { font-size: 40px; }
  .welcome-text h2 { font-size: 19px; }
  .task-cards { grid-template-columns: 1fr; gap: 10px; }
  .task-card { display: flex; align-items: center; gap: 14px; text-align: left; padding: 14px 16px; }
  .task-card-body { flex: 1; }
  .task-card-icon { font-size: 26px; margin-bottom: 0; }
  .task-card-count { font-size: 24px; }
  .stats-row { grid-template-columns: repeat(4, 1fr); gap: 8px; }
  .stat-item { padding: 10px 4px; }
  .stat-num { font-size: 17px; }
  .timer-display { flex-direction: column; gap: 12px; padding: 14px; }
  .timer-time { font-size: 36px; }
  .upcoming-bar-label { font-size: 10px; }

  /* ---------- 学习页 ---------- */
  .study-container { max-width: none; }
  .study-header { flex-wrap: wrap; gap: 8px; }
  .study-timer { font-size: 17px; padding: 5px 12px; }
  .flashcard { padding: 18px 16px; border-radius: var(--radius-md); }
  .flashcard-content { font-size: 15px; }
  .flashcard-actions { flex-direction: row; gap: 10px; margin-top: 16px; }
  .flashcard-actions .btn { flex: 1; white-space: normal; padding: 12px 8px; }
  .study-footer { margin-top: 16px; }
  .review-history { margin-top: 16px; }

  /* 完成页 / 打卡成功页 */
  .study-complete, .checkin-success { padding: 24px 8px; }
  .complete-icon, .checkin-icon { font-size: 52px; }
  .complete-stats, .checkin-stats { grid-template-columns: repeat(2, 1fr); gap: 10px; }
  .complete-actions, .checkin-actions { flex-direction: column; gap: 10px; }
  .complete-actions .btn, .checkin-actions .btn { width: 100%; min-height: 46px; }

  /* ---------- 日历 ---------- */
  .calendar-page { max-width: none; }
  .calendar-header h2 { font-size: 18px; }
  .calendar-month-stats { gap: 6px 12px; font-size: 12px; }
  .calendar-grid { padding: 8px; gap: 3px; }
  .calendar-day { min-height: 44px; padding: 2px; }
  .calendar-day .cal-day-num { font-size: 13px; }
  .calendar-day .cal-day-check { font-size: 14px; margin: 0; }
  .calendar-day .cal-day-detail { display: none; }
  .calendar-nav { margin-bottom: 12px; }
  .calendar-legend { gap: 10px 14px; }
  .legend-item { font-size: 12px; }

  /* ---------- 题库 ---------- */
  .library-page, .item-detail-page { max-width: none; }
  .library-page h2 { font-size: 18px; margin-bottom: 14px; }
  .chapter-header { padding: 14px 16px; flex-wrap: wrap; gap: 6px; }
  .chapter-header h3 { font-size: 14px; }
  .chapter-items { padding: 0 6px 6px; }
  .library-item { padding: 12px 8px; }
  .item-question {
    white-space: normal;
    display: -webkit-box;
    -webkit-line-clamp: 2;
    -webkit-box-orient: vertical;
    overflow: hidden;
    font-size: 14px;
  }
  .item-detail-card { padding: 18px 16px; }
  .item-detail-content { font-size: 15px; }

  /* ---------- 统计页 ---------- */
  .stats-page { max-width: none; }
  .stats-page h2 { font-size: 18px; margin-bottom: 14px; }
  .stats-overview { grid-template-columns: repeat(2, 1fr); gap: 10px; margin-bottom: 16px; }
  .stat-card { padding: 14px 10px; }
  .stat-card-value { font-size: 20px; }
  .stats-section { padding: 16px 14px; }
  .heatmap { grid-template-columns: repeat(7, 1fr); gap: 3px; }
  .heatmap-cell { min-height: 38px; }
  .heatmap-day { font-size: 11px; }
  .heatmap-label { font-size: 8px; }
  .chapter-stat-item { grid-template-columns: 1fr; gap: 4px; }
  .chapter-stat-name { font-size: 14px; }
  .settings-grid { grid-template-columns: 1fr; gap: 10px; }
  .settings-actions { flex-wrap: wrap; }
  .settings-actions .btn { flex: 1; }

  /* ---------- 云同步卡片 ---------- */
  .cloudsync-row { flex-direction: column; align-items: stretch; }
  .cloudsync-input { min-width: 0; width: 100%; font-size: 16px; }
  .cloudsync-row .btn { width: 100%; }
  .cloudsync-check { justify-content: flex-start; }
  .cloudsync-box { padding: 12px; }

  /* ---------- 模态框 → 底部弹出面板 ---------- */
  .modal-overlay { align-items: flex-end; }
  .modal-content {
    width: 100%;
    max-width: none;
    max-height: 82vh;
    border-radius: 18px 18px 0 0;
    animation: modalSheetUp 0.28s ease;
  }
  @keyframes modalSheetUp {
    from { opacity: 0; transform: translateY(60px); }
    to { opacity: 1; transform: translateY(0); }
  }
  .modal-body { padding: 16px; padding-bottom: calc(16px + env(safe-area-inset-bottom)); }
  .modal-stats { flex-wrap: wrap; gap: 10px 16px; }
}

/* ========== 模态框 ========== */
.modal-overlay {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: rgba(0, 0, 0, 0.45);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 1000;
  animation: fadeIn 0.2s ease;
}

.modal-content {
  background: var(--color-card-bg);
  border-radius: var(--radius-lg);
  max-width: 500px;
  width: 90%;
  max-height: 80vh;
  overflow-y: auto;
  box-shadow: 0 8px 32px rgba(0, 0, 0, 0.2);
  animation: modalSlideIn 0.25s ease;
}

@keyframes modalSlideIn {
  from { opacity: 0; transform: scale(0.95) translateY(20px); }
  to { opacity: 1; transform: scale(1) translateY(0); }
}

.modal-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 16px 20px;
  border-bottom: 1px solid var(--color-border-light);
}

.modal-header h3 {
  font-size: 18px;
  font-weight: 600;
}

.modal-close {
  background: none;
  border: none;
  font-size: 20px;
  cursor: pointer;
  color: var(--color-text-tertiary);
  padding: 4px 8px;
  border-radius: var(--radius-sm);
  transition: var(--transition);
}

.modal-close:hover {
  background: var(--color-bg);
  color: var(--color-text);
}

.modal-body { padding: 20px; }

.modal-status {
  font-size: 14px;
  font-weight: 600;
  margin-bottom: 16px;
  color: var(--color-primary);
}

.modal-stats {
  display: flex;
  gap: 20px;
  padding: 12px 16px;
  background: var(--color-bg);
  border-radius: var(--radius-sm);
  margin-bottom: 16px;
}

.modal-stat {
  display: flex;
  align-items: center;
  gap: 6px;
  font-size: 14px;
  color: var(--color-text-secondary);
  font-weight: 500;
}

.modal-stat-icon { font-size: 18px; }

.modal-section { margin-bottom: 16px; }

.modal-section-title {
  font-size: 13px;
  font-weight: 600;
  color: var(--color-text-secondary);
  margin-bottom: 8px;
}

.modal-item-list {
  list-style: none;
  padding: 0;
}

.modal-item-list li {
  padding: 8px 12px;
  background: var(--color-bg);
  border-radius: var(--radius-sm);
  margin-bottom: 4px;
  font-size: 13px;
  color: var(--color-text);
  line-height: 1.5;
}

/* 动画 */
@keyframes fadeIn {
  from { opacity: 0; transform: translateY(10px); }
  to { opacity: 1; transform: translateY(0); }
}

#main-content > * {
  animation: fadeIn 0.3s ease;
}

/* 答案配图 */
.answer-image {
  max-width: 100%;
  height: auto;
  border-radius: var(--radius-md);
  margin-top: 12px;
  box-shadow: var(--shadow-sm);
  background: #fff;
}

.answer-images {
  display: flex;
  flex-direction: column;
  gap: 12px;
  margin-top: 4px;
}

.answer-image {
  cursor: zoom-in;
  transition: opacity 0.2s;
}
.answer-image:active { opacity: 0.85; }

/* 图片全屏放大预览 */
.image-preview-overlay {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: rgba(0, 0, 0, 0.88);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 3000;
  cursor: zoom-out;
  padding: 16px;
  animation: fadeIn 0.2s ease;
}
.image-preview-overlay img {
  max-width: 100%;
  max-height: 100%;
  object-fit: contain;
  border-radius: 8px;
  box-shadow: 0 8px 40px rgba(0, 0, 0, 0.5);
}
.image-preview-overlay .preview-hint {
  position: absolute;
  bottom: calc(16px + env(safe-area-inset-bottom));
  left: 50%;
  transform: translateX(-50%);
  color: rgba(255, 255, 255, 0.7);
  font-size: 12px;
  background: rgba(0, 0, 0, 0.5);
  padding: 6px 14px;
  border-radius: 16px;
  pointer-events: none;
}

/* ===== 云同步卡片 ===== */
.cloudsync-box {
  background: #f8faff;
  border: 1px solid #dbe4ff;
  border-radius: 10px;
  padding: 14px;
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.cloudsync-tip {
  font-size: 13px;
  color: #5b6472;
  line-height: 1.6;
  background: #eef3ff;
  border-radius: 8px;
  padding: 10px 12px;
}

.cloudsync-tip a {
  color: #4a6cf7;
}

.cloudsync-row {
  display: flex;
  align-items: center;
  gap: 10px;
  flex-wrap: wrap;
}

.cloudsync-input {
  flex: 1;
  min-width: 200px;
  padding: 8px 12px;
  border: 1px solid #d0d7e5;
  border-radius: 8px;
  font-size: 14px;
  outline: none;
  transition: border-color 0.2s;
  background: #fff;
  color: inherit;
}

select.cloudsync-input {
  cursor: pointer;
  appearance: auto;
}

.cloudsync-input:focus {
  border-color: #4a6cf7;
}

.cloudsync-check {
  display: flex;
  align-items: center;
  gap: 6px;
  font-size: 14px;
  color: #3a4356;
  cursor: pointer;
}

.cloudsync-status {
  font-size: 13px;
  color: #4a6cf7;
  background: #eef3ff;
  border-radius: 8px;
  padding: 8px 12px;
}