:root {
  --primary: #4f6ef7;
  --primary-dark: #3b56d9;
  --primary-light: #eef1fe;
  --bg: #f5f6fa;
  --card: #ffffff;
  --text: #1f2430;
  --text-2: #5a6478;
  --text-3: #8a93a8;
  --border: #e4e7f0;
  --green: #16a34a;
  --green-bg: #eaf7ef;
  --red: #dc2626;
  --red-bg: #fdeeee;
  --orange: #d97706;
  --orange-bg: #fdf3e7;
  --shadow: 0 1px 3px rgba(31, 36, 48, .06), 0 4px 14px rgba(31, 36, 48, .05);
  --radius: 12px;
}
* { margin: 0; padding: 0; box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  font-family: "PingFang SC", "Microsoft YaHei", "Segoe UI", system-ui, sans-serif;
  background: var(--bg);
  color: var(--text);
  font-size: 15px;
  line-height: 1.75;
}
#app { display: flex; min-height: 100vh; }

/* ============ 侧边栏 ============ */
.sidebar {
  width: 272px; flex-shrink: 0;
  background: var(--card);
  border-right: 1px solid var(--border);
  height: 100vh; position: sticky; top: 0;
  display: flex; flex-direction: column;
  overflow-y: auto;
}
.brand { display: flex; align-items: center; gap: 12px; padding: 20px 18px 16px; }
.brand-logo {
  width: 42px; height: 42px; border-radius: 10px;
  background: linear-gradient(135deg, var(--primary), #7c5cfc);
  color: #fff; font-weight: 800; font-size: 13px;
  display: flex; align-items: center; justify-content: center;
  letter-spacing: .5px;
}
.brand-text { display: flex; flex-direction: column; line-height: 1.35; }
.brand-text strong { font-size: 15px; }
.brand-text span { font-size: 12px; color: var(--text-3); }
.nav { padding: 4px 12px; display: flex; flex-direction: column; gap: 2px; }
.nav-item {
  display: flex; align-items: center; gap: 8px;
  padding: 9px 12px; border-radius: 8px;
  text-decoration: none; color: var(--text-2);
  font-size: 14px; transition: all .15s;
}
.nav-item:hover { background: var(--primary-light); color: var(--primary); }
.nav-item.active { background: var(--primary); color: #fff; font-weight: 600; }
.side-label {
  padding: 16px 20px 6px; font-size: 12px; color: var(--text-3);
  letter-spacing: 1px; font-weight: 600;
}
.chapter-nav { gap: 2px; }
.chapter-item {
  display: flex; align-items: center; gap: 10px;
  padding: 9px 12px; border-radius: 8px;
  text-decoration: none; color: var(--text-2); font-size: 13.5px;
  transition: all .15s; line-height: 1.4;
}
.chapter-item:hover { background: var(--primary-light); color: var(--primary); }
.chapter-item.active { background: var(--primary-light); color: var(--primary); font-weight: 600; }
.chapter-item .idx {
  width: 22px; height: 22px; border-radius: 6px; flex-shrink: 0;
  background: #eef0f6; color: var(--text-3);
  font-size: 11px; font-weight: 700;
  display: flex; align-items: center; justify-content: center;
}
.chapter-item.done .idx { background: var(--green); color: #fff; }
.chapter-item.active .idx { background: var(--primary); color: #fff; }
.chapter-item .c-title { flex: 1; }
.chapter-item .c-score { font-size: 11px; color: var(--text-3); font-weight: 600; }
.chapter-item.done .c-score { color: var(--green); }
.side-footer { margin-top: auto; padding: 16px; }
.goal-card {
  background: linear-gradient(135deg, #4f6ef7, #7c5cfc);
  border-radius: 10px; padding: 12px 14px; color: #fff;
}
.goal-title { font-size: 12px; opacity: .85; margin-bottom: 4px; }
.goal-text { font-size: 13px; line-height: 1.6; }
.goal-text b { font-size: 15px; }

/* ============ 主区域 ============ */
.main { flex: 1; padding: 32px 40px 80px; max-width: 1080px; margin: 0 auto; width: 100%; }

.page-head { margin-bottom: 24px; }
.page-head h1 { font-size: 24px; margin-bottom: 6px; }
.page-head p { color: var(--text-2); font-size: 14px; }

/* ============ 仪表盘 ============ */
.stat-grid { display: grid; grid-template-columns: repeat(4, 1fr); gap: 16px; margin-bottom: 24px; }
.stat-card {
  background: var(--card); border-radius: var(--radius);
  padding: 18px 20px; box-shadow: var(--shadow);
  border: 1px solid var(--border);
}
.stat-card .stat-label { font-size: 12.5px; color: var(--text-3); margin-bottom: 6px; }
.stat-card .stat-value { font-size: 26px; font-weight: 800; color: var(--primary); }
.stat-card .stat-sub { font-size: 12px; color: var(--text-3); margin-top: 2px; }

.panel {
  background: var(--card); border-radius: var(--radius);
  box-shadow: var(--shadow); border: 1px solid var(--border);
  margin-bottom: 20px; overflow: hidden;
}
.panel-head {
  display: flex; align-items: center; justify-content: space-between;
  padding: 16px 20px; border-bottom: 1px solid var(--border);
}
.panel-head h2 { font-size: 16px; }
.panel-head .hint { font-size: 12.5px; color: var(--text-3); }
.panel-body { padding: 20px; }

.progress-row {
  display: flex; align-items: center; gap: 14px;
  padding: 12px 0; border-bottom: 1px dashed var(--border);
}
.progress-row:last-child { border-bottom: none; }
.progress-row .p-name { width: 220px; flex-shrink: 0; font-size: 13.5px; font-weight: 600; }
.progress-row .p-bar { flex: 1; height: 8px; background: #eef0f6; border-radius: 99px; overflow: hidden; }
.progress-row .p-bar i {
  display: block; height: 100%; border-radius: 99px;
  background: linear-gradient(90deg, var(--primary), #7c5cfc);
}
.progress-row .p-num { width: 64px; text-align: right; font-size: 13px; font-weight: 700; color: var(--text-2); }

table.records { width: 100%; border-collapse: collapse; font-size: 13.5px; }
table.records th {
  text-align: left; padding: 10px 12px; color: var(--text-3);
  font-size: 12.5px; border-bottom: 1px solid var(--border); white-space: nowrap;
}
table.records td { padding: 10px 12px; border-bottom: 1px solid #f0f2f8; vertical-align: middle; }
table.records tr:last-child td { border-bottom: none; }
.score-pill {
  display: inline-block; padding: 2px 10px; border-radius: 99px;
  font-size: 12.5px; font-weight: 700;
}
.score-pill.good { background: var(--green-bg); color: var(--green); }
.score-pill.mid { background: var(--orange-bg); color: var(--orange); }
.score-pill.bad { background: var(--red-bg); color: var(--red); }
.empty-tip { text-align: center; color: var(--text-3); padding: 40px 0; font-size: 14px; }

.btn {
  display: inline-flex; align-items: center; gap: 6px;
  border: none; cursor: pointer; border-radius: 8px;
  padding: 9px 18px; font-size: 14px; font-weight: 600;
  font-family: inherit; transition: all .15s;
}
.btn-primary { background: var(--primary); color: #fff; }
.btn-primary:hover { background: var(--primary-dark); }
.btn-ghost { background: #eef0f6; color: var(--text-2); }
.btn-ghost:hover { background: #e2e5ef; color: var(--text); }
.btn-sm { padding: 6px 12px; font-size: 12.5px; }
.btn:disabled { opacity: .45; cursor: not-allowed; }
.btn:disabled:hover { background: #eef0f6; color: var(--text-2); }

/* ============ 复习 ============ */
.review-nudge {
  display: flex; align-items: center; justify-content: space-between; gap: 14px; flex-wrap: wrap;
  background: linear-gradient(135deg, #fff7ed, #ffedd5);
  border: 1px solid #fdba74; border-radius: var(--radius);
  padding: 14px 20px; margin-bottom: 20px; box-shadow: var(--shadow);
}
.review-nudge.soft { background: #f5f7fc; border-color: var(--border); }
.review-nudge .rn-text { font-size: 14px; }
.review-nudge .rn-text b { color: var(--orange); }
.review-actions { display: flex; gap: 10px; flex-wrap: wrap; align-items: center; }
.q-card .q-text .q-src {
  font-size: 11px; font-weight: 600; color: var(--primary);
  background: var(--primary-light); border-radius: 5px; padding: 1px 7px;
  margin-left: 8px; vertical-align: 2px; white-space: nowrap;
}
.wrong-pill {
  display: inline-block; padding: 2px 10px; border-radius: 99px;
  font-size: 12.5px; font-weight: 700; background: var(--red-bg); color: var(--red);
}

/* ============ 章节页 ============ */
.chapter-hero {
  background: linear-gradient(135deg, #4f6ef7 0%, #7c5cfc 100%);
  border-radius: var(--radius); color: #fff;
  padding: 28px 32px; margin-bottom: 24px;
  box-shadow: var(--shadow);
}
.chapter-hero .ch-no { font-size: 13px; opacity: .8; margin-bottom: 6px; letter-spacing: 1px; }
.chapter-hero h1 { font-size: 26px; margin-bottom: 10px; }
.chapter-hero .ch-goal { font-size: 14px; opacity: .92; max-width: 720px; }
.chapter-hero .ch-meta { display: flex; gap: 10px; margin-top: 16px; flex-wrap: wrap; }
.chapter-hero .ch-meta span {
  background: rgba(255,255,255,.18); border-radius: 99px;
  padding: 3px 12px; font-size: 12.5px;
}
.study-bar {
  display: flex; align-items: center; gap: 12px; flex-wrap: wrap;
  background: var(--card); border: 1px solid var(--border);
  border-radius: var(--radius); padding: 12px 18px; margin-bottom: 20px;
  box-shadow: var(--shadow);
}
/* .study-bar .timer 已随实时计时展示下线（章节页只留操作按钮，
   学习时长在结束/提交时汇总，见 quiz.js 学习栏注释） */
.study-bar .spacer { flex: 1; }

.doc {
  background: var(--card); border-radius: var(--radius);
  border: 1px solid var(--border); box-shadow: var(--shadow);
  padding: 32px 36px; margin-bottom: 28px;
}
.doc h2 { font-size: 20px; margin: 28px 0 12px; padding-bottom: 8px; border-bottom: 2px solid var(--primary-light); }
.doc h2:first-child { margin-top: 0; }
.doc h3 { font-size: 16.5px; margin: 22px 0 8px; color: var(--primary-dark); }
.doc h4 { font-size: 15px; margin: 16px 0 6px; }
.doc p { margin: 8px 0; }
.doc ul, .doc ol { margin: 8px 0 8px 22px; }
.doc li { margin: 3px 0; }
.doc strong { color: var(--primary-dark); }
.doc code {
  background: #f0f2f8; border-radius: 5px; padding: 1px 6px;
  font-family: Consolas, "Courier New", monospace; font-size: 13px; color: #c2410c;
}
.doc pre {
  background: #1e2433; color: #e6e9f2; border-radius: 10px;
  padding: 16px 18px; overflow-x: auto; margin: 12px 0;
  font-family: Consolas, "Courier New", monospace; font-size: 13px; line-height: 1.65;
}
.doc pre code { background: none; color: inherit; padding: 0; }
.doc blockquote {
  border-left: 4px solid var(--primary); background: var(--primary-light);
  padding: 10px 16px; margin: 12px 0; border-radius: 0 8px 8px 0;
  color: var(--text-2); font-size: 14px;
}
.doc table { width: 100%; border-collapse: collapse; margin: 12px 0; font-size: 13.5px; }
.doc th { background: #f5f7fc; text-align: left; padding: 8px 12px; border: 1px solid var(--border); font-weight: 700; }
.doc td { padding: 8px 12px; border: 1px solid var(--border); vertical-align: top; }
.doc hr { border: none; border-top: 1px dashed var(--border); margin: 24px 0; }

/* ============ 题目 ============ */
.quiz-section-title {
  display: flex; align-items: center; gap: 10px;
  font-size: 19px; margin: 28px 0 14px;
}
.quiz-section-title .q-badge {
  background: var(--primary); color: #fff; border-radius: 8px;
  font-size: 13px; padding: 2px 10px; font-weight: 700;
}
.q-type-title {
  font-size: 15px; font-weight: 700; color: var(--text-2);
  margin: 22px 0 10px; display: flex; align-items: center; gap: 8px;
}
.q-type-title::before { content: ""; width: 4px; height: 16px; background: var(--primary); border-radius: 2px; }

.q-card {
  background: var(--card); border: 1px solid var(--border);
  border-radius: var(--radius); padding: 18px 20px; margin-bottom: 14px;
  box-shadow: var(--shadow);
}
.q-card.correct { border-color: var(--green); }
.q-card.wrong { border-color: var(--red); }
.q-card .q-head { display: flex; gap: 10px; margin-bottom: 10px; }
.q-card .q-no {
  flex-shrink: 0; width: 26px; height: 26px; border-radius: 7px;
  background: var(--primary-light); color: var(--primary);
  font-size: 13px; font-weight: 800;
  display: flex; align-items: center; justify-content: center;
}
.q-card .q-text { flex: 1; font-weight: 600; line-height: 1.6; }
.q-card .q-text .q-tag {
  font-size: 11px; font-weight: 700; color: var(--orange);
  background: var(--orange-bg); border-radius: 5px; padding: 1px 7px;
  margin-left: 8px; vertical-align: 2px;
}
.q-options { display: flex; flex-direction: column; gap: 8px; margin-left: 36px; }
.q-option {
  display: flex; align-items: flex-start; gap: 10px;
  border: 1.5px solid var(--border); border-radius: 9px;
  padding: 9px 14px; cursor: pointer; transition: all .12s;
  font-size: 14px; line-height: 1.55;
}
.q-option:hover { border-color: var(--primary); background: var(--primary-light); }
.q-option.selected { border-color: var(--primary); background: var(--primary-light); }
.q-option.picked-correct { border-color: var(--green); background: var(--green-bg); }
.q-option.picked-wrong { border-color: var(--red); background: var(--red-bg); }
.q-option.locked { cursor: default; }
.q-option.locked:hover { background: inherit; }
.q-option .opt-key {
  flex-shrink: 0; width: 22px; height: 22px; border-radius: 6px;
  border: 1.5px solid var(--border); background: #fff;
  font-size: 12px; font-weight: 700; color: var(--text-2);
  display: flex; align-items: center; justify-content: center;
}
.q-option.selected .opt-key { border-color: var(--primary); background: var(--primary); color: #fff; }
.q-option.picked-correct .opt-key { border-color: var(--green); background: var(--green); color: #fff; }
.q-option.picked-wrong .opt-key { border-color: var(--red); background: var(--red); color: #fff; }
.q-option .opt-text { flex: 1; }

.q-input, .q-textarea {
  width: 100%; border: 1.5px solid var(--border); border-radius: 9px;
  padding: 10px 14px; font-size: 14px; font-family: inherit;
  margin-left: 36px; width: calc(100% - 36px);
  transition: border-color .12s; background: #fff; color: var(--text);
}
.q-input:focus, .q-textarea:focus { outline: none; border-color: var(--primary); }
.q-textarea { min-height: 110px; resize: vertical; line-height: 1.65; }
.q-input.miss { border-color: var(--red); background: var(--red-bg); }
.q-input.hit { border-color: var(--green); background: var(--green-bg); }

.q-explain {
  margin: 12px 0 0 36px; border-radius: 9px;
  background: #f7f8fc; border: 1px dashed var(--border);
  padding: 10px 14px; font-size: 13.5px; color: var(--text-2);
}
.q-explain .lbl { font-weight: 700; color: var(--primary-dark); margin-right: 6px; }
.q-explain.correct { background: var(--green-bg); border-color: var(--green); }
.q-explain.wrong { background: var(--red-bg); border-color: var(--red); }
.q-score-line { margin: 10px 0 0 36px; font-size: 13px; font-weight: 700; }
.q-score-line.ok { color: var(--green); }
.q-score-line.no { color: var(--red); }

.ref-block {
  margin: 12px 0 0 36px; border-radius: 9px;
  border: 1px solid var(--border); background: #fafbfe; padding: 14px 16px;
}
.ref-block .ref-title { font-weight: 700; font-size: 13.5px; margin-bottom: 8px; color: var(--primary-dark); }
.ref-block .ref-answer { font-size: 13.5px; color: var(--text-2); white-space: pre-wrap; }
.kp-list { margin-top: 12px; display: flex; flex-direction: column; gap: 6px; }
.kp-item {
  display: flex; align-items: flex-start; gap: 8px; font-size: 13.5px;
  cursor: pointer; user-select: none;
}
.kp-item input { margin-top: 4px; accent-color: var(--primary); }
.kp-item .kp-text { flex: 1; }
.kp-note { font-size: 12.5px; color: var(--text-3); margin-top: 8px; }

/* ============ 成绩单 ============ */
.result-card {
  background: var(--card); border-radius: var(--radius);
  border: 1px solid var(--border); box-shadow: var(--shadow);
  padding: 32px; margin-bottom: 24px; text-align: center;
}
.result-card .band { font-size: 15px; font-weight: 800; letter-spacing: 1px; }
.result-card .band.A { color: var(--green); }
.result-card .band.B { color: var(--primary); }
.result-card .band.C { color: var(--orange); }
.result-card .band.D { color: var(--red); }
.result-card .score-num { font-size: 56px; font-weight: 800; margin: 6px 0; }
.result-card .score-sub { color: var(--text-3); font-size: 13px; }
.result-eval {
  background: #fafbfe; border: 1px solid var(--border); border-radius: 10px;
  padding: 18px 20px; margin-top: 20px; text-align: left;
  font-size: 14px; line-height: 1.8;
}
.result-eval h4 { margin-bottom: 8px; font-size: 14.5px; }
.result-eval ul { margin: 6px 0 6px 20px; }
.type-breakdown { display: grid; grid-template-columns: repeat(5, 1fr); gap: 10px; margin-top: 18px; }
.tb-item { background: #f5f7fc; border-radius: 9px; padding: 10px 8px; }
.tb-item .tb-name { font-size: 12px; color: var(--text-3); }
.tb-item .tb-val { font-size: 17px; font-weight: 800; margin-top: 2px; }

.submit-bar {
  display: flex; align-items: center; gap: 14px; flex-wrap: wrap;
  background: var(--card); border: 1px solid var(--border);
  border-radius: var(--radius); padding: 16px 20px;
  box-shadow: var(--shadow); margin: 24px 0 40px;
  position: sticky; bottom: 16px;
}
.submit-bar .sb-info { font-size: 13px; color: var(--text-2); flex: 1; }
.submit-bar .sb-info b { color: var(--primary); }

.toast {
  position: fixed; left: 50%; bottom: 32px; transform: translateX(-50%);
  background: #1f2430; color: #fff; border-radius: 10px;
  padding: 10px 22px; font-size: 14px; box-shadow: 0 8px 24px rgba(0,0,0,.25);
  opacity: 0; pointer-events: none; transition: opacity .25s, transform .25s;
  z-index: 99;
}
.toast.show { opacity: 1; transform: translateX(-50%) translateY(-6px); }

@media (max-width: 900px) {
  .sidebar { width: 220px; }
  .main { padding: 20px 16px 60px; }
  .stat-grid { grid-template-columns: repeat(2, 1fr); }
  .type-breakdown { grid-template-columns: repeat(3, 1fr); }
  .doc { padding: 20px; }
}

/* ============ 课程目录模块分组（T03 重构新增，仅追加不动现有规则） ============ */
/* 组头复用 .side-label；此处仅做与章节项的左对齐微调（抵消 .nav 的 12px 内边距） */
.chapter-nav .side-label { padding: 14px 12px 4px; }
.chapter-nav .side-label:first-child { padding-top: 6px; }

/* ============ code 手撕代码题型（T05 新增，仅追加不动现有规则） ============ */
/* 等宽代码编辑区：与 .q-input/.q-textarea 同一左缩进（36px）保持题卡对齐 */
.q-code {
  display: block; width: calc(100% - 36px); margin-left: 36px;
  border: 1.5px solid var(--border); border-radius: 9px;
  padding: 12px 14px; font-size: 13.5px; line-height: 1.7;
  font-family: ui-monospace, SFMono-Regular, Consolas, "Courier New", monospace;
  background: #fafbfe; color: var(--text);
  min-height: 180px; resize: vertical; tab-size: 4;
  transition: border-color .12s, background .12s;
}
.q-code:focus { outline: none; border-color: var(--primary); background: #fff; }
.q-code:disabled { background: #f0f2f8; color: var(--text-2); cursor: default; }

/* 「查看参考实现」按钮行（仅未提交时显示） */
.code-actions { margin: 10px 0 0 36px; display: flex; align-items: center; gap: 10px; flex-wrap: wrap; }
.code-actions .code-reveal-btn { flex-shrink: 0; }
.code-reveal-hint { font-size: 12px; color: var(--text-3); }

/* 已查看参考实现的明示条（自动检查轨失效） */
.code-revealed-tip {
  margin: 10px 0 0 36px; border-radius: 8px; padding: 8px 12px;
  background: var(--orange-bg); border: 1px solid var(--orange);
  color: var(--orange); font-size: 12.5px; font-weight: 600;
}

/* 提交后：参考实现代码块（深色底，与 .doc pre 视觉一致） */
.code-ref-pre {
  background: #1e2433; color: #e6e9f2; border-radius: 10px;
  padding: 14px 16px; overflow-x: auto; margin: 4px 0 2px;
  font-family: ui-monospace, SFMono-Regular, Consolas, "Courier New", monospace;
  font-size: 13px; line-height: 1.65;
}
.code-ref-pre code { background: none; color: inherit; padding: 0; font-family: inherit; }

/* 提交后：自动检查逐项 ✓/✗ 列表 */
.code-checks { margin-top: 12px; }
.code-checks-title { font-size: 13px; font-weight: 700; color: var(--text-2); margin-bottom: 6px; }
.code-checks ul { list-style: none; display: flex; flex-direction: column; gap: 4px; }
.code-checks li { display: flex; align-items: flex-start; gap: 8px; font-size: 13.5px; line-height: 1.6; }
.code-checks li .ck { flex-shrink: 0; width: 16px; text-align: center; font-weight: 800; }
.code-checks li.hit .ck { color: var(--green); }
.code-checks li.miss .ck { color: var(--red); }
.code-checks li.miss .ck-label { color: var(--text-3); }

/* 成绩单题型分布：题型扩展为 7 种后自适应换行（≤5 种时与原 5 列布局一致） */
.type-breakdown { grid-template-columns: repeat(auto-fit, minmax(96px, 1fr)); }

/* ============ 移动端适配（T12-a：≤720px 顶部品牌栏 + 底部固定导航 + 顶部横滑章节条） ============ */
/* 策略：本块只追加、不改动上方任何既有规则——桌面端（>720px）匹配不到本媒体查询，
   1440px 视觉零变化由结构保证。窄屏布局完全由 CSS 重排实现，零 DOM/JS 变更。 */
@media (max-width: 720px) {
  /* —— 侧边栏 → 顶部品牌栏（脱离文档流，主内容全宽） —— */
  .sidebar {
    position: fixed; top: 0; left: 0; right: 0;
    width: 100%; height: auto;
    display: block; overflow: visible;
    border-right: none; border-bottom: 1px solid var(--border);
    box-shadow: 0 1px 6px rgba(31, 36, 48, .05);
    z-index: 50;
  }
  .brand { height: 54px; padding: 0 14px; }
  .brand-logo { width: 34px; height: 34px; border-radius: 9px; font-size: 12px; }
  .brand-text strong { font-size: 14px; }
  .brand-text span { font-size: 11px; }

  /* —— 一级导航 → 底部固定导航（四入口：学习档案/复习中心/学习计划/数据管理） —— */
  .sidebar > .nav:not(.chapter-nav) {
    position: fixed; bottom: 0; left: 0; right: 0;
    flex-direction: row; gap: 0;
    padding: 4px 4px calc(4px + env(safe-area-inset-bottom));
    background: var(--card);
    border-top: 1px solid var(--border);
    box-shadow: 0 -2px 12px rgba(31, 36, 48, .06);
    z-index: 51;
  }
  .nav-item {
    flex: 1; min-width: 0; min-height: 50px;
    justify-content: center; text-align: center;
    font-size: 11.5px; padding: 6px 2px;
    white-space: nowrap;
  }
  /* 已下架功能入口（模拟面试/闪卡记忆）在底部导航隐藏；
     待 index.html 下架清理后这两个选择器自然失配，无需二次改动 */
  .nav-item[data-nav="mock"], .nav-item[data-nav="flash"] { display: none; }

  /* —— 课程目录 → 主内容顶部的横向滚动章节条（纯 CSS 无 DOM 变更下，
     「可折叠抽屉/下拉选择器」的最稳健等价形态：点选即走、不遮挡内容） —— */
  .sidebar > .side-label { display: none; } /* 「课程目录」标签由横滑条形态替代 */
  .chapter-nav {
    position: fixed; top: 54px; left: 0; right: 0;
    flex-direction: row; align-items: center; gap: 6px;
    padding: 8px 12px;
    overflow-x: auto; overflow-y: hidden;
    background: var(--card); border-bottom: 1px solid var(--border);
    -webkit-overflow-scrolling: touch; scrollbar-width: none;
    z-index: 49;
  }
  .chapter-nav::-webkit-scrollbar { display: none; }
  .chapter-nav .side-label { /* 模块组头 → 横滑条内的分隔标签 */
    flex-shrink: 0; padding: 4px 2px; font-size: 11px; letter-spacing: 0;
  }
  .chapter-item {
    flex-shrink: 0; white-space: nowrap;
    padding: 6px 10px; border-radius: 99px;
    background: #f5f7fc; border: 1px solid transparent;
    font-size: 12.5px;
  }
  .chapter-item .idx { width: 18px; height: 18px; font-size: 10px; border-radius: 5px; }
  .chapter-item .c-score { display: none; } /* chips 内省略分数，进章节页看详情 */
  .chapter-item.active { border-color: var(--primary); }

  .side-footer { display: none; } /* 目标卡片移动端省略（底部导航常驻） */

  /* —— 主内容区：让出顶部「品牌栏 54px + 章节条约 46px」与底部导航 —— */
  .main {
    max-width: none; margin: 0;
    padding: 108px 14px calc(78px + env(safe-area-inset-bottom));
  }

  /* —— 通用紧凑化（仅 ≤720px 生效） —— */
  .page-head h1 { font-size: 20px; }
  .stat-card { padding: 14px 16px; }
  .stat-card .stat-value { font-size: 22px; }
  .panel-body { padding: 14px; }
  .chapter-hero { padding: 20px 18px; }
  .chapter-hero h1 { font-size: 21px; }
  .doc { padding: 18px 16px; }
  .result-card { padding: 22px 16px; }
  .result-card .score-num { font-size: 44px; }
  .progress-row { flex-wrap: wrap; gap: 8px; }
  .progress-row .p-name { width: 100%; }
  .progress-row .p-num { width: auto; margin-left: auto; }
  table.records th, table.records td { padding: 8px 8px; font-size: 12.5px; }
  /* 题卡 36px 缩进在窄屏回收：选项/输入/解析/参考实现满宽 */
  .q-options, .q-explain, .ref-block, .code-actions, .code-revealed-tip { margin-left: 0; }
  .q-input, .q-textarea, .q-code { margin-left: 0; width: 100%; }
  /* 悬浮元素抬到底部导航之上（safe-area 适配） */
  .submit-bar { bottom: calc(78px + env(safe-area-inset-bottom)); padding: 12px 14px; }
  .toast { bottom: calc(86px + env(safe-area-inset-bottom)); }
}