/* ============================================================
   learning Web App — 全局设计系统（映射 common/GLOBAL_*.md）
   颜色唯一来源：common/GLOBAL_COLOR_SYSTEM.md
   产品 Token 登记：learning/docs/DESIGN-SYSTEM.md
   ============================================================ */

/* ---------- 1. 主题与语义 Token ---------- */
:root {
  color-scheme: light;

  /* 颜色（浅色） */
  --background: #CCD0CF;
  --surface: #F7F8F8;
  --surface-elevated: #FFFFFF;
  --surface-variant: #E7EAEA;

  --primary: #253745;
  --primary-strong: #11212D;
  --primary-container: #9BA8AB;
  --on-primary: #FFFFFF;

  --text-primary: #06141B;
  --text-secondary: #4A5C6A;
  --text-tertiary: #6F7D82;
  --text-disabled: #9BA8AB;

  --icon-primary: #253745;
  --icon-secondary: #4A5C6A;
  --icon-disabled: #9BA8AB;

  --border: #9BA8AB;
  --divider: #CCD0CF;
  --overlay: rgba(6, 20, 27, 0.4);
  --scrim: rgba(6, 20, 27, 0.28);

  --success: #2E7D5B;
  --warning: #B7791F;
  --error: #C94A4A;
  --info: #3F718A;
  --on-success: #FFFFFF;
  --on-error: #FFFFFF;

  /* 产品级语义浅底 / 焦点 / 强调卡（登记于 docs/DESIGN-SYSTEM.md） */
  --tint-primary: rgba(37, 55, 69, 0.1);
  --tint-success: rgba(46, 125, 91, 0.12);
  --tint-error: rgba(201, 74, 74, 0.12);
  --tint-warning: rgba(183, 121, 31, 0.12);
  --focus-ring: #253745;
  --hero: #4A5C6A;
  --on-hero: #FFFFFF;
  --on-hero-sub: #CCD0CF;
  --on-hero-divider: rgba(204, 208, 207, 0.28);

  --shadow: 0 10px 28px rgba(6, 20, 27, 0.12);
  --shadow-soft: 0 2px 8px rgba(6, 20, 27, 0.08);
  --shadow-faint: 0 1px 2px rgba(6, 20, 27, 0.08);
  --shadow-active: 0 1px 3px rgba(6, 20, 27, 0.12);
  --shadow-nav: 0 -2px 10px rgba(6, 20, 27, 0.05);

  /* 字体 */
  --font: -apple-system, BlinkMacSystemFont, "SF Pro Text", "PingFang SC",
    "Hiragino Sans GB", "Microsoft YaHei", "Segoe UI", Roboto, "Noto Sans CJK SC", sans-serif;
  --font-mono: ui-monospace, "SF Mono", "Geist Mono", Consolas, Menlo, monospace;

  /* 排版角色 */
  --text-display: 28px;
  --text-headline: 22px;
  --text-title: 17px;
  --text-body: 16px;
  --text-body-small: 14px;
  --text-caption: 12px;
  --text-label: 13px;

  /* 间距刻度 4 基准 */
  --space-1: 4px;
  --space-2: 8px;
  --space-3: 12px;
  --space-4: 16px;
  --space-5: 20px;
  --space-6: 24px;
  --space-7: 32px;
  --space-8: 40px;
  --space-9: 48px;
  --space-10: 64px;

  /* 圆角 */
  --radius-xs: 6px;
  --radius-sm: 10px;
  --radius-md: 14px;
  --radius-lg: 18px;
  --radius-xl: 24px;
  --radius-full: 999px;

  /* 动效 */
  --duration-fast: 120ms;
  --duration-std: 200ms;
  --duration-slow: 280ms;
  --ease: cubic-bezier(0.33, 0, 0.2, 1);
}

:root[data-mode="dark"] {
  color-scheme: dark;

  --background: #06141B;
  --surface: #11212D;
  --surface-elevated: #253745;
  --surface-variant: #253745;

  --primary: #4A5C6A;
  --primary-strong: #9BA8AB;
  --primary-container: #11212D;
  --on-primary: #FFFFFF;

  --text-primary: #CCD0CF;
  --text-secondary: #9BA8AB;
  --text-tertiary: #6F7D82;
  --text-disabled: #4A5C6A;

  --icon-primary: #CCD0CF;
  --icon-secondary: #9BA8AB;
  --icon-disabled: #4A5C6A;

  --border: #253745;
  --divider: #253745;
  --overlay: rgba(0, 0, 0, 0.5);
  --scrim: rgba(0, 0, 0, 0.3);

  --success: #6FBF9A;
  --warning: #D9A44A;
  --error: #E58A8A;
  --info: #7FB4CC;
  --on-success: #06141B;
  --on-error: #06141B;

  --tint-primary: rgba(204, 208, 207, 0.12);
  --tint-success: rgba(111, 191, 154, 0.14);
  --tint-error: rgba(229, 138, 138, 0.14);
  --tint-warning: rgba(217, 164, 74, 0.16);
  --focus-ring: #9BA8AB;
  --hero: #253745;
  --on-hero: #FFFFFF;
  --on-hero-sub: #CCD0CF;
  --on-hero-divider: rgba(204, 208, 207, 0.2);

  --shadow: 0 10px 28px rgba(0, 0, 0, 0.35);
  --shadow-soft: 0 2px 8px rgba(0, 0, 0, 0.25);
  --shadow-faint: 0 1px 2px rgba(0, 0, 0, 0.18);
  --shadow-active: 0 1px 3px rgba(0, 0, 0, 0.28);
  --shadow-nav: 0 -2px 10px rgba(0, 0, 0, 0.3);
}

/* ---------- 2. Base ---------- */
*,
*::before,
*::after { box-sizing: border-box; }

html { -webkit-text-size-adjust: 100%; }

body {
  margin: 0;
  font-family: var(--font);
  font-size: var(--text-body);
  line-height: 1.6;
  color: var(--text-primary);
  background: var(--background);
  min-height: 100dvh;
  -webkit-font-smoothing: antialiased;
  -webkit-tap-highlight-color: transparent;
}

button,
input,
select,
textarea {
  font: inherit;
  color: inherit;
}

button { -webkit-tap-highlight-color: transparent; }

a { color: var(--info); }

::selection { background: var(--tint-primary); color: var(--text-primary); }

::-webkit-scrollbar { width: 8px; height: 8px; }
::-webkit-scrollbar-track { background: transparent; }
::-webkit-scrollbar-thumb { background: var(--border); border-radius: var(--radius-full); }

:focus-visible {
  outline: 2px solid var(--focus-ring);
  outline-offset: 2px;
}

.icon { display: inline-block; flex: none; }
.icon svg { display: block; }
.icon-label { font-size: 0; }

/* 桌面/平板主导航中的分段导航 */
.top-tabs {
  display: none;
  align-items: center;
  gap: var(--space-1);
  padding: 3px;
  background: var(--surface-variant);
  border-radius: var(--radius-sm);
}
.top-tabs .tab {
  min-height: 34px;
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 0 16px;
  border-radius: var(--radius-xs);
  text-decoration: none;
  font-size: var(--text-label);
  font-weight: 600;
  color: var(--text-secondary);
  white-space: nowrap;
  transition: background var(--duration-fast) var(--ease), color var(--duration-fast) var(--ease);
}
.top-tabs .tab:hover { color: var(--text-primary); }
.top-tabs .tab[aria-current="page"],
.top-tabs .tab.active {
  background: var(--surface-elevated);
  color: var(--text-primary);
  box-shadow: var(--shadow-faint);
}
.top-tabs .tab svg { width: 17px; height: 17px; }

/* ---------- 3. App Bar ---------- */
.app-header {
  position: relative;
  z-index: 100;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-4);
  padding: env(safe-area-inset-top, 0px) var(--space-5) 0 var(--space-5);
  min-height: 58px;
  background: var(--surface);
  border-bottom: 1px solid var(--divider);
}
.app-header-inner {
  width: min(100%, 1180px);
  margin: 0 auto;
  display: flex;
  align-items: center;
  gap: var(--space-4);
  min-height: 57px;
}
.brand {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  text-decoration: none;
  color: var(--text-primary);
  min-width: 0;
}
.brand-mark {
  width: 34px;
  height: 34px;
  border-radius: var(--radius-sm);
  background: var(--primary);
  color: var(--on-primary);
  display: inline-flex;
  align-items: center;
  justify-content: center;
  flex: none;
}
.brand-mark svg { width: 19px; height: 19px; }
.brand-name {
  font-size: var(--text-title);
  font-weight: 700;
  letter-spacing: -0.01em;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}
.brand-sub {
  color: var(--text-secondary);
  font-size: var(--text-caption);
  font-weight: 400;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}
.app-header-right {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  margin-left: auto;
  flex: none;
}
.icon-button {
  width: 44px;
  height: 44px;
  border: none;
  border-radius: var(--radius-sm);
  background: transparent;
  color: var(--icon-secondary);
  display: inline-flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  transition: background var(--duration-fast) var(--ease), color var(--duration-fast) var(--ease);
}
.icon-button:hover { background: var(--tint-primary); color: var(--icon-primary); }
.icon-button:active { transform: scale(0.96); }
.icon-button svg { width: 21px; height: 21px; }

/* 明暗主题图标切换（light 显示月亮 = 可切到暗；dark 显示太阳 = 可切到亮） */
:root[data-mode="light"] .icon-sun,
:root[data-mode="dark"] .icon-moon { display: none; }

/* ---------- 4. 手机端底部 Tab ---------- */
.bottom-tabs {
  position: fixed;
  left: 0;
  right: 0;
  bottom: 0;
  z-index: 220;
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  background: var(--surface-elevated);
  border-top: 1px solid var(--divider);
  padding-bottom: env(safe-area-inset-bottom, 0px);
  box-shadow: var(--shadow-nav);
}
.bottom-tabs .tab {
  position: relative;
  min-height: 56px;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 2px;
  text-decoration: none;
  color: var(--text-secondary);
  font-size: 11px;
  font-weight: 500;
  letter-spacing: 0.01em;
  -webkit-tap-highlight-color: transparent;
}
.bottom-tabs .tab svg { width: 22px; height: 22px; color: var(--icon-secondary); }
.bottom-tabs .tab[aria-current="page"],
.bottom-tabs .tab.active { color: var(--text-primary); }
.bottom-tabs .tab[aria-current="page"] svg,
.bottom-tabs .tab.active svg { color: var(--icon-primary); }
.bottom-tabs .tab[aria-current="page"]::before,
.bottom-tabs .tab.active::before {
  content: "";
  position: absolute;
  top: 4px;
  width: 16px;
  height: 3px;
  border-radius: var(--radius-full);
  background: var(--primary);
}
body.has-bottom-tabs { padding-bottom: calc(56px + env(safe-area-inset-bottom, 0px)); }
body.immersive .bottom-tabs { display: none; }

/* ---------- 5. 上下文操作条 / 页面工具条 ---------- */
.overview-bar {
  position: relative;
  z-index: 90;
  display: flex;
  align-items: center;
  gap: var(--space-3);
  min-height: 52px;
  padding: 6px max(var(--space-5), env(safe-area-inset-right, 0px)) 6px
    max(var(--space-5), env(safe-area-inset-left, 0px));
  background: var(--surface);
  border-bottom: 1px solid var(--divider);
}
.overview-inner {
  width: min(100%, 1180px);
  margin: 0 auto;
  display: flex;
  align-items: center;
  gap: var(--space-3);
  min-width: 0;
}
.page-name {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  font-size: var(--text-title);
  font-weight: 700;
  color: var(--text-primary);
  white-space: nowrap;
  flex: none;
}
.page-name svg { width: 18px; height: 18px; color: var(--icon-secondary); }
.overview-actions {
  margin-left: auto;
  display: flex;
  align-items: center;
  gap: var(--space-2);
  min-width: 0;
}

/* 次级动作按钮（错题本/成绩记录/卡片管理 等） */
.knowledge-toggle,
.action-btn {
  min-height: 38px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 6px;
  padding: 0 13px;
  border: 1px solid transparent;
  border-radius: var(--radius-sm);
  background: var(--tint-primary);
  color: var(--primary);
  font-size: var(--text-label);
  font-weight: 600;
  text-decoration: none;
  cursor: pointer;
  white-space: nowrap;
  transition: background var(--duration-fast) var(--ease), color var(--duration-fast) var(--ease),
    border-color var(--duration-fast) var(--ease);
}
.knowledge-toggle:hover,
.action-btn:hover { background: var(--surface-variant); color: var(--primary-strong); }
.knowledge-toggle:active,
.action-btn:active { transform: scale(0.98); }
.knowledge-toggle svg,
.action-btn svg { width: 16px; height: 16px; }

/* 通用按钮语义：primary / secondary / ghost / danger */
.btn {
  min-height: 44px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 0 18px;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  background: var(--surface);
  color: var(--text-primary);
  font-size: var(--text-body-small);
  font-weight: 600;
  line-height: 1.4;
  cursor: pointer;
  text-decoration: none;
  white-space: nowrap;
  transition: background var(--duration-fast) var(--ease), color var(--duration-fast) var(--ease),
    border-color var(--duration-fast) var(--ease), opacity var(--duration-fast) var(--ease);
}
.btn:hover:not(:disabled) { border-color: var(--primary-container); color: var(--text-primary); }
.btn:active:not(:disabled) { transform: scale(0.98); }
.btn:disabled { opacity: 0.45; cursor: default; }
.btn svg { width: 17px; height: 17px; }

.btn-primary {
  background: var(--primary);
  border-color: var(--primary);
  color: var(--on-primary);
}
.btn-primary:hover:not(:disabled) {
  background: var(--primary-strong);
  border-color: var(--primary-strong);
  color: var(--on-primary);
}

.btn-secondary {
  background: var(--surface-elevated);
  border-color: var(--border);
}
.btn-ghost {
  background: transparent;
  border-color: transparent;
  color: var(--primary);
}
.btn-danger {
  background: transparent;
  border-color: var(--error);
  color: var(--error);
}
.btn-danger:hover:not(:disabled) { background: var(--tint-error); }
.btn-sm { min-height: 34px; padding: 0 12px; font-size: var(--text-caption); }
.btn-block { width: 100%; }
.btn.active { background: var(--tint-primary); border-color: var(--primary); color: var(--primary); }

/* 兼容旧类名（JS 模板与历史 HTML 仍在用） */
.back-btn,
.modal-close {
  min-height: 38px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 6px;
  padding: 0 13px;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  background: var(--surface);
  color: var(--text-secondary);
  font-size: var(--text-label);
  font-weight: 600;
  cursor: pointer;
  text-decoration: none;
  white-space: nowrap;
  transition: background var(--duration-fast) var(--ease), color var(--duration-fast) var(--ease),
    border-color var(--duration-fast) var(--ease);
}
.back-btn:hover:not(:disabled),
.modal-close:hover:not(:disabled) { border-color: var(--primary); color: var(--primary); }
.back-btn:active:not(:disabled),
.modal-close:active:not(:disabled) { transform: scale(0.98); }
.back-btn:disabled { opacity: 0.4; cursor: default; }

/* ---------- 6. 页面滚动容器与内容宽度 ---------- */
.home,
.ov-wrap {
  flex: 1;
  min-height: 0;
  overflow-y: auto;
  padding: var(--space-5) var(--space-5) calc(var(--space-9) + env(safe-area-inset-bottom, 0px));
  -webkit-overflow-scrolling: touch;
}
.home-inner {
  width: min(100%, 1000px);
  margin: 0 auto;
}
.ov-wrap {
  width: min(100%, 1000px);
  margin: 0 auto;
}
.home-header {
  display: flex;
  align-items: center;
  gap: var(--space-4);
  margin-bottom: var(--space-4);
  flex-wrap: wrap;
}
.home-title {
  font-size: var(--text-display);
  font-weight: 800;
  letter-spacing: -0.02em;
  color: var(--text-primary);
}
.home-sub {
  width: 100%;
  font-size: var(--text-body-small);
  color: var(--text-tertiary);
}
.home-empty,
.wrong-empty,
.rv-empty,
.mg-empty {
  padding: var(--space-9) var(--space-4);
  text-align: center;
  font-size: var(--text-body-small);
  color: var(--text-tertiary);
  line-height: 1.8;
}

/* 分段选择（类别切换） */
.cat-switch {
  display: inline-flex;
  padding: 3px;
  gap: 3px;
  background: var(--surface-variant);
  border-radius: var(--radius-sm);
  flex: none;
}
.cat-switch-btn {
  min-height: 34px;
  padding: 0 18px;
  border: none;
  border-radius: var(--radius-xs);
  background: transparent;
  color: var(--text-secondary);
  font-size: var(--text-label);
  font-weight: 600;
  cursor: pointer;
  white-space: nowrap;
  transition: background var(--duration-fast) var(--ease), color var(--duration-fast) var(--ease);
}
.cat-switch-btn:hover { color: var(--text-primary); }
.cat-switch-btn.active {
  background: var(--surface-elevated);
  color: var(--text-primary);
  box-shadow: var(--shadow-active);
}

/* ---------- 7. 目录 / 列表卡片（题库与大纲共用） ---------- */
.quiz-card {
  background: var(--surface-elevated);
  border: 1px solid var(--divider);
  border-radius: var(--radius-lg);
  overflow: hidden;
}

.group-title {
  min-height: 44px;
  display: flex;
  align-items: center;
  padding: 0 var(--space-5);
  background: var(--surface);
  color: var(--text-secondary);
  font-size: var(--text-label);
  font-weight: 700;
  letter-spacing: 0.03em;
}

.chapter-title {
  min-height: 52px;
  display: flex;
  align-items: center;
  gap: var(--space-3);
  padding: 4px var(--space-5);
  color: var(--text-primary);
  font-size: var(--text-title);
  font-weight: 700;
}
.chapter-title.divider { border-top: 1px solid var(--divider); }
.chapter-title .ch-name {
  min-width: 0;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}
.chapter-title .ch-badge { margin-left: auto; }
.chapter-title .ch-badge,
.chapter-title .sec-score {
  flex: none;
  color: var(--text-secondary);
  font-size: var(--text-body-small);
  font-weight: 600;
  font-variant-numeric: tabular-nums;
}
.ch-actions {
  margin-left: auto;
  display: flex;
  align-items: center;
  gap: var(--space-2);
  flex: none;
}
.ch-wrong-count { color: var(--error); font-size: var(--text-caption); font-weight: 600; }
.ch-test-btn {
  min-height: 30px;
  padding: 0 12px;
  border: 1px solid var(--primary-container);
  border-radius: var(--radius-full);
  background: var(--tint-primary);
  color: var(--primary);
  font-size: var(--text-caption);
  font-weight: 600;
  cursor: pointer;
  white-space: nowrap;
  transition: background var(--duration-fast) var(--ease), color var(--duration-fast) var(--ease);
}
.ch-test-btn:hover { background: var(--primary); color: var(--on-primary); border-color: var(--primary); }

.section-row {
  position: relative;
  min-height: 52px;
  display: flex;
  align-items: center;
  gap: var(--space-3);
  padding: 4px var(--space-5);
  border-top: 1px solid var(--divider);
  cursor: pointer;
  transition: background var(--duration-fast) var(--ease);
}
.section-row:first-of-type { border-top: none; }
.section-row:hover { background: var(--surface); }
.section-row:active { background: var(--surface-variant); }
.section-row .sec-num {
  flex: none;
  min-width: 64px;
  color: var(--text-secondary);
  font-size: var(--text-label);
  font-weight: 600;
  font-variant-numeric: tabular-nums;
}
.section-row .sec-name {
  flex: 1;
  min-width: 0;
  color: var(--text-primary);
  font-size: var(--text-body);
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}
.section-row .q-count {
  flex: none;
  display: flex;
  flex-direction: column;
  align-items: flex-end;
  gap: 5px;
}
.section-row .q-count-text {
  color: var(--text-tertiary);
  font-size: var(--text-body-small);
  font-variant-numeric: tabular-nums;
  white-space: nowrap;
}
.section-row .q-num {
  min-width: 3ch;
  display: inline-block;
  text-align: center;
  font-variant-numeric: tabular-nums;
}
.q-progress {
  width: 104px;
  height: 4px;
  border-radius: var(--radius-full);
  background: var(--surface-variant);
  overflow: hidden;
}
.q-progress-fill {
  height: 100%;
  border-radius: var(--radius-full);
  background: var(--primary-container);
  transition: width var(--duration-slow) var(--ease);
}
.sec-score { margin-left: auto; }
.sec-num + .sec-name { min-width: 0; }

/* 筛选 chips / 小标签按钮 */
.chips {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  flex-wrap: wrap;
}
.chips:empty { display: none; }
.chip {
  min-height: 32px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 0 12px;
  border: 1px solid var(--border);
  border-radius: var(--radius-full);
  background: var(--surface);
  color: var(--text-secondary);
  font-size: var(--text-caption);
  font-weight: 500;
  cursor: pointer;
  white-space: nowrap;
  transition: background var(--duration-fast) var(--ease), color var(--duration-fast) var(--ease),
    border-color var(--duration-fast) var(--ease);
}
.chip:hover { border-color: var(--primary); color: var(--primary); }
.chip.on {
  background: var(--primary);
  border-color: var(--primary);
  color: var(--on-primary);
  font-weight: 600;
}
.icon-btn {
  min-height: 34px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 6px;
  padding: 0 12px;
  border: 1px solid var(--border);
  border-radius: var(--radius-full);
  background: var(--surface);
  color: var(--text-secondary);
  font-size: var(--text-caption);
  font-weight: 600;
  cursor: pointer;
  white-space: nowrap;
  transition: background var(--duration-fast) var(--ease), color var(--duration-fast) var(--ease),
    border-color var(--duration-fast) var(--ease);
}
.icon-btn:hover { border-color: var(--primary); color: var(--primary); }
.icon-btn.on { background: var(--tint-warning); border-color: var(--warning); color: var(--warning); }
.icon-btn.marked { background: var(--tint-primary); border-color: var(--primary); color: var(--primary); }

/* ---------- 8. 章节筛选 / 编辑页顶部工具 ---------- */
.sec-toolbar {
  position: relative;
  z-index: 80;
  display: flex;
  align-items: center;
  gap: var(--space-2);
  padding: 8px max(var(--space-5), env(safe-area-inset-right, 0px)) 8px
    max(var(--space-5), env(safe-area-inset-left, 0px));
  background: var(--surface);
  border-bottom: 1px solid var(--divider);
  flex-wrap: wrap;
}
.sec-toolbar[hidden] { display: none; }
.sec-toolbar .tb-label {
  color: var(--text-tertiary);
  font-size: var(--text-body-small);
  white-space: nowrap;
}
.tb-select,
.rv-select {
  min-height: 40px;
  min-width: 150px;
  max-width: 46vw;
  padding: 0 34px 0 12px;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  background: var(--surface-elevated);
  color: var(--text-primary);
  font-size: var(--text-body-small);
  outline: none;
}
.tb-select:disabled { opacity: 0.5; cursor: not-allowed; }
.tb-select:focus-visible,
.rv-select:focus-visible { outline: 2px solid var(--focus-ring); outline-offset: 1px; }
.sec-toolbar .tb-back { margin-left: auto; }

.layout {
  flex: 1;
  min-height: 0;
  display: flex;
}
.content {
  flex: 1;
  min-width: 0;
  display: flex;
  flex-direction: column;
  background: var(--background);
  overflow: hidden;
}
.content-inner {
  flex: 1;
  min-height: 0;
  display: flex;
  flex-direction: column;
  overflow: hidden;
}
.content-inner > div[hidden] { display: none; }
#view-overview { flex: 1; min-height: 0; display: flex; flex-direction: column; overflow: hidden; }
#view-overview .ov-wrap { flex: 1; min-height: 0; overflow-y: auto; }

/* 编辑/管理顶栏 */
.editor-topbar {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  padding: 8px max(var(--space-4), env(safe-area-inset-right, 0px)) 8px
    max(var(--space-4), env(safe-area-inset-left, 0px));
  background: var(--surface);
  border-bottom: 1px solid var(--divider);
  flex-wrap: wrap;
}
.editor-crumb {
  min-width: 0;
  display: inline-flex;
  align-items: center;
  gap: 6px;
  flex-wrap: wrap;
  color: var(--text-secondary);
  font-size: var(--text-body-small);
}
.editor-crumb .crumb-sep { color: var(--text-tertiary); }
.editor-crumb .crumb-cur { color: var(--text-primary); font-weight: 700; }
.editor-topbar .spacer { flex: 1; }
.editor-pos {
  color: var(--text-tertiary);
  font-size: var(--text-caption);
  font-variant-numeric: tabular-nums;
  white-space: nowrap;
}

/* ---------- 9. 弹层 / 加载 ---------- */
.modal-overlay {
  position: fixed;
  inset: 0;
  z-index: 300;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: var(--space-5);
  background: var(--overlay);
  animation: fade-in var(--duration-fast) var(--ease);
}
.modal {
  width: min(92vw, 420px);
  max-height: min(82dvh, 720px);
  overflow-y: auto;
  padding: var(--space-6);
  border-radius: var(--radius-lg);
  background: var(--surface-elevated);
  box-shadow: var(--shadow);
  animation: rise-in var(--duration-std) var(--ease);
}
.modal-wide { width: min(94vw, 560px); }
.modal-title {
  font-size: var(--text-title);
  font-weight: 700;
  color: var(--text-primary);
  display: flex;
  align-items: center;
  gap: 8px;
}
.modal-sub {
  margin: 4px 0 var(--space-4);
  color: var(--text-tertiary);
  font-size: var(--text-body-small);
  line-height: 1.7;
}
.modal-opt {
  display: flex;
  flex-direction: column;
  align-items: flex-start;
  gap: 3px;
  width: 100%;
  padding: var(--space-3) var(--space-4);
  margin-bottom: var(--space-3);
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  background: var(--surface);
  text-align: left;
  cursor: pointer;
  transition: border-color var(--duration-fast) var(--ease), background var(--duration-fast) var(--ease);
}
.modal-opt:hover { border-color: var(--primary); background: var(--surface-variant); }
.mo-name { font-size: var(--text-body); font-weight: 600; color: var(--text-primary); }
.mo-desc { font-size: var(--text-body-small); color: var(--text-secondary); }
.modal-close { width: 100%; }
.modal-actions {
  display: flex;
  gap: var(--space-3);
  margin-top: var(--space-3);
}
.modal-actions .modal-close { flex: 1; width: auto; }
.modal-confirm {
  min-height: 44px;
  flex: 1;
  border: none;
  border-radius: var(--radius-sm);
  background: var(--primary);
  color: var(--on-primary);
  font-size: var(--text-body-small);
  font-weight: 600;
  cursor: pointer;
  transition: background var(--duration-fast) var(--ease);
}
.modal-confirm:hover { background: var(--primary-strong); }

.loading-overlay {
  position: fixed;
  inset: 0;
  z-index: 400;
  display: flex;
  align-items: center;
  justify-content: center;
  background: var(--overlay);
}
.loading-box {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  padding: var(--space-3) var(--space-6);
  border-radius: var(--radius-md);
  background: var(--surface-elevated);
  color: var(--text-primary);
  font-size: var(--text-body-small);
  box-shadow: var(--shadow);
}
.loading-box::before {
  content: "";
  width: 16px;
  height: 16px;
  border-radius: 50%;
  border: 2px solid var(--surface-variant);
  border-top-color: var(--primary);
  animation: spin 0.8s linear infinite;
}

@keyframes fade-in {
  from { opacity: 0; }
  to { opacity: 1; }
}
@keyframes rise-in {
  from { opacity: 0; transform: translateY(10px) scale(0.99); }
  to { opacity: 1; transform: none; }
}
@keyframes spin {
  to { transform: rotate(360deg); }
}

/* ---------- 10. 响应式：手机 / iPad / 桌面 ---------- */
@media (min-width: 768px) {
  .top-tabs { display: inline-flex; }
  .bottom-tabs { display: none; }
  body.has-bottom-tabs { padding-bottom: 0; }
  .home,
  .ov-wrap { padding: var(--space-6) var(--space-6) var(--space-10); }
}

@media (max-width: 767.98px) {
  .app-header {
    padding-left: var(--space-3);
    padding-right: var(--space-3);
    gap: var(--space-2);
  }
  .app-header-inner { gap: var(--space-2); }
  .brand-sub { display: none; }
  .overview-bar {
    padding-left: var(--space-3);
    padding-right: var(--space-3);
    min-height: 48px;
  }
  .page-name { font-size: var(--text-body); }
  .overview-actions {
    overflow-x: auto;
    flex-wrap: nowrap;
    scrollbar-width: none;
  }
  .overview-actions::-webkit-scrollbar { display: none; }
  .home,
  .ov-wrap {
    padding: var(--space-4) var(--space-4) calc(72px + env(safe-area-inset-bottom, 0px));
  }
  .chapter-title { min-height: 48px; }
  .section-row { min-height: 52px; }
  .section-row .sec-num { min-width: 48px; font-size: var(--text-caption); }
  .section-row .q-count-text { font-size: var(--text-caption); }
  .q-progress { width: 76px; }
  .group-title { padding: 0 var(--space-4); }
  .chapter-title,
  .section-row { padding-left: var(--space-4); padding-right: var(--space-4); }
  .ch-test-btn { min-height: 32px; }
  .home-title { font-size: 24px; }
  .modal { padding: var(--space-5); border-radius: var(--radius-lg); }
  .sec-toolbar { padding-left: var(--space-3); padding-right: var(--space-3); }
  .sec-toolbar .tb-label { display: none; }
  .tb-select { flex: 1 1 0; min-width: 0; max-width: none; }
}

/* 平板竖屏与桌面之间的中间宽度：保持限宽与舒适行高 */
@media (min-width: 768px) and (max-width: 1099.98px) {
  .home-inner { width: min(100%, 860px); }
  .top-tabs .tab { padding: 0 12px; }
}

/* ---------- 11. 动效与无障碍 ---------- */
@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
  }
}

@media (max-width: 767.98px) and (hover: none) {
  .section-row:hover,
  .knowledge-toggle:hover,
  .action-btn:hover,
  .icon-button:hover,
  .chip:hover,
  .icon-btn:hover { background: none; }
}