/* ============================================================
   关卡页面通用外壳：导航 / 课文 / 交互 / 题目 / 底部导航
   ============================================================ */

/* ===== 顶部导航 ===== */
.sq-nav {
  position: sticky;
  top: 0;
  background: rgba(248, 245, 238, 0.92);
  backdrop-filter: blur(8px);
  border-bottom: 1px solid var(--line-soft);
  z-index: 100;
}
.sq-nav-inner {
  max-width: 960px;
  margin: 0 auto;
  padding: 14px 32px;
  display: flex;
  justify-content: space-between;
  align-items: center;
}
.sq-brand {
  font-family: var(--display);
  font-size: 16px;
  font-weight: 500;
  letter-spacing: 0.18em;
  color: var(--ink);
  text-decoration: none;
}
.sq-brand .dot { color: var(--accent); margin: 0 4px; }
.sq-progress-pill {
  font-family: var(--display);
  font-size: 11.5px;
  letter-spacing: 0.22em;
  color: var(--muted);
  padding: 6px 12px;
  border: 1px solid var(--line);
  border-radius: 2px;
}

/* ===== 关卡页主容器 ===== */
.sq-level {
  max-width: 880px;
  margin: 0 auto;
  padding: 48px 32px 100px;
}

/* 关卡 hero */
.sq-level-hero {
  text-align: center;
  margin-bottom: 48px;
  padding-bottom: 32px;
  border-bottom: 1px solid var(--line-soft);
}
.sq-level-hero .label {
  font-family: var(--display);
  font-size: 12px;
  letter-spacing: 0.32em;
  color: var(--gold);
  text-transform: uppercase;
  margin-bottom: 14px;
}
.sq-level-hero h1 {
  font-family: var(--serif-cn);
  font-size: 30px;
  font-weight: 500;
  letter-spacing: 0.04em;
  margin-bottom: 6px;
}
.sq-level-hero .en-title {
  font-family: var(--display);
  font-size: 14px;
  letter-spacing: 0.24em;
  color: var(--muted);
  margin-top: 10px;
}

/* ===== Section 通用 ===== */
.sq-section {
  margin-bottom: 56px;
}
.sq-section-label {
  font-family: var(--display);
  font-size: 11.5px;
  letter-spacing: 0.32em;
  color: var(--gold);
  text-transform: uppercase;
  margin-bottom: 16px;
  padding-bottom: 8px;
  border-bottom: 1px solid var(--line-soft);
}

/* ===== 课文 lesson ===== */
.sq-lesson p {
  margin-bottom: 16px;
  color: var(--ink-soft);
  font-size: 18.5px;
  line-height: 1.9;
}
.sq-lesson p strong {
  color: var(--ink);
  font-weight: 500;
}
.sq-lesson .callout {
  margin: 22px 0;
  padding: 18px 22px;
  background: var(--bg-soft);
  border-left: 3px solid var(--gold);
  font-size: 17px;
  color: var(--ink-soft);
  line-height: 1.85;
}
.sq-lesson .lesson-h {
  font-family: var(--serif-cn);
  font-size: 21px;
  font-weight: 500;
  color: var(--ink);
  margin: 30px 0 12px;
  padding-bottom: 6px;
  border-bottom: 1px solid var(--line-soft);
  letter-spacing: 0.02em;
}
.sq-lesson .lesson-figure {
  margin: 24px 0 28px;
  padding: 18px 14px 14px;
  background: var(--bg);
  border: 1px solid var(--line-soft);
  border-radius: 2px;
}
.sq-lesson .lesson-figure svg {
  display: block;
  width: 100%;
  height: auto;
}
.sq-lesson .lesson-figure figcaption {
  margin-top: 10px;
  font-size: 13.5px;
  font-style: italic;
  color: var(--muted);
  text-align: center;
  line-height: 1.6;
}

/* 课文里的对照表（如 总体 vs 样本变量名 / SD vs SE） */
.sq-lesson .vars-table {
  width: 100%;
  border-collapse: collapse;
  font-family: var(--serif-cn);
  font-size: 14.5px;
  color: var(--ink);
}
.sq-lesson .vars-table thead th {
  text-align: left;
  padding: 12px 14px 10px;
  border-bottom: 1.5px solid var(--ink-soft);
  font-family: var(--display);
  font-size: 11.5px;
  letter-spacing: 0.18em;
  font-weight: 500;
  color: var(--gold);
  text-transform: uppercase;
  vertical-align: bottom;
}
.sq-lesson .vars-table th .th-en {
  display: inline-block;
  margin-top: 4px;
  font-family: var(--serif-cn);
  font-size: 11.5px;
  letter-spacing: 0;
  font-weight: 400;
  color: var(--muted);
  text-transform: none;
}
.sq-lesson .vars-table td {
  padding: 12px 14px;
  border-bottom: 1px dashed var(--line);
  vertical-align: middle;
  line-height: 1.55;
}
.sq-lesson .vars-table tbody tr:last-child td {
  border-bottom: none;
}
.sq-lesson .vars-table .vsym {
  font-family: var(--serif-en);
  font-size: 17px;
  color: var(--ink);
}
.sq-lesson .vars-table .vname {
  margin-left: 6px;
  font-family: var(--serif-en);
  font-size: 12px;
  color: var(--muted);
  font-style: italic;
}
.sq-lesson .vars-table td .th-en {
  display: block;
  margin-top: 3px;
  font-family: var(--serif-cn);
  font-size: 12px;
  color: var(--muted);
  font-style: italic;
}
.sq-lesson .vars-table.compact td {
  padding: 10px 14px;
  font-size: 14px;
}

/* 数据样例表（如 L1 三种数据结构） */
.sq-lesson .data-sample-table {
  width: 100%;
  border-collapse: collapse;
  font-family: var(--serif-cn);
  font-size: 14px;
  color: var(--ink);
}
.sq-lesson .data-sample-table thead th {
  text-align: left;
  padding: 9px 12px;
  background: var(--bg-soft);
  border-bottom: 1.5px solid var(--ink-soft);
  font-weight: 500;
  font-size: 13px;
  color: var(--ink);
  font-family: var(--serif-cn);
  letter-spacing: 0;
  text-transform: none;
}
.sq-lesson .data-sample-table tbody td {
  padding: 7px 12px;
  border-bottom: 1px dashed var(--line);
  font-variant-numeric: tabular-nums;
}
.sq-lesson .data-sample-table tbody tr:last-child td { border-bottom: none; }
.sq-lesson .data-sample-table td.num,
.sq-lesson .data-sample-table th.num { text-align: right; }
.sq-lesson .data-sample-table tbody tr:hover {
  background: var(--bg-soft);
}

/* 课文里的多行公式块（displayMode KaTeX 堆叠） */
.sq-lesson .formula-stack {
  display: flex;
  flex-direction: column;
  gap: 4px;
  align-items: center;
  padding: 4px 0;
}
.sq-lesson .formula-stack > div {
  width: 100%;
  text-align: center;
}

/* SVG 自绘公式块（行级 SVG，根号是 path 一笔画的笔画 stroke） */
.sq-lesson .svg-formula-stack {
  display: flex;
  flex-direction: column;
  gap: 6px;
  align-items: center;
  padding: 6px 0;
}
.sq-lesson .svg-formula-stack .svg-formula {
  display: block;
  width: 100%;
  max-width: 720px;
  height: auto;
  color: var(--ink);
}

/* 纯 HTML/CSS 数学公式（不依赖 KaTeX，分数 + 根号 + vinculum） */
.sq-lesson .math-stack {
  display: flex;
  flex-direction: column;
  gap: 22px;
  align-items: center;
  padding: 18px 8px 14px;
  font-family: "Times New Roman", "Source Han Serif SC", "Songti SC", serif;
  font-size: 22px;
  color: var(--ink);
  line-height: 1;
}
.sq-lesson .math-stack .math-row {
  display: flex;
  align-items: center;
  flex-wrap: wrap;
  justify-content: center;
  gap: 10px;
}
.sq-lesson .math-stack .m-eq { padding: 0 4px; }
.sq-lesson .math-stack .m-it { font-style: italic; }
.sq-lesson .math-stack .m-text { font-style: normal; }
.sq-lesson .math-stack .m-paren {
  font-size: 0.78em;
  color: var(--muted);
  margin-left: 2px;
}
.sq-lesson .math-stack .m-gap { width: 36px; }
.sq-lesson .math-stack .m-note {
  font-size: 0.72em;
  color: var(--muted);
  font-style: normal;
  margin-left: 12px;
}

/* 分数 */
.sq-lesson .math-stack .m-frac {
  display: inline-flex;
  flex-direction: column;
  align-items: center;
  vertical-align: middle;
  line-height: 1.05;
}
.sq-lesson .math-stack .m-num {
  padding: 0 10px 4px;
  border-bottom: 1.4px solid currentColor;
  min-width: 28px;
  text-align: center;
}
.sq-lesson .math-stack .m-den {
  padding: 5px 10px 0;
  min-width: 28px;
  text-align: center;
}

/* 根号：用 unicode √ + vinculum overline */
.sq-lesson .math-stack .m-sqrt {
  display: inline-flex;
  align-items: flex-start;
  position: relative;
}
.sq-lesson .math-stack .m-sqrt::before {
  content: "√";
  font-size: 1.1em;
  line-height: 1;
  margin-right: -2px;
}
.sq-lesson .math-stack .m-rad {
  display: inline-block;
  border-top: 1.4px solid currentColor;
  padding: 1px 4px 0;
  line-height: 1.05;
}

/* SE 上的 hat 帽子 */
.sq-lesson .math-stack .m-hat {
  position: relative;
  display: inline-block;
  padding-top: 2px;
}
.sq-lesson .math-stack .m-hat::before {
  content: "^";
  position: absolute;
  top: -10px;
  left: 50%;
  transform: translateX(-50%);
  font-size: 0.85em;
  font-weight: 600;
}

/* 互动正上方的引导句（每关复用） */
.cue {
  margin: 4px 0 18px;
  padding: 12px 16px;
  background: var(--bg-soft);
  border-left: 3px solid var(--gold);
  font-size: 15px;
  line-height: 1.7;
  color: var(--ink-soft);
}
.cue strong { color: var(--ink); font-weight: 500; }

/* 互动后的延伸说明（如 68/95 经验法则） */
.post-cue {
  margin: 18px 0 0;
  padding: 14px 18px;
  background: var(--bg-soft);
  border-left: 3px solid var(--ink-soft);
  font-size: 14.5px;
  line-height: 1.75;
  color: var(--ink-soft);
}
.post-cue strong { color: var(--ink); font-weight: 500; }
.post-cue .post-cue-label {
  display: block;
  font-family: var(--display);
  font-size: 11px;
  letter-spacing: 0.24em;
  color: var(--muted);
  text-transform: uppercase;
  margin-bottom: 6px;
}

/* ===== 交互区 ===== */
.sq-interactive {
  background: white;
  border: 1px solid var(--line);
  border-radius: 4px;
  padding: 28px 30px;
}
.sq-interactive .stats-row {
  display: flex;
  gap: 24px;
  flex-wrap: wrap;
  margin-bottom: 24px;
  padding-bottom: 18px;
  border-bottom: 1px dashed var(--line);
}
.sq-stat {
  display: flex;
  flex-direction: column;
  min-width: 100px;
}
.sq-stat .label {
  font-family: var(--display);
  font-size: 11px;
  letter-spacing: 0.24em;
  color: var(--muted);
  text-transform: uppercase;
  margin-bottom: 4px;
}
.sq-stat .value {
  font-family: var(--serif-en);
  font-size: 24px;
  font-weight: 500;
  color: var(--ink);
}
.sq-stat .value.muted { color: var(--muted); }

.sq-canvas-wrap {
  margin: 24px 0;
}
.sq-canvas-wrap svg {
  display: block;
  width: 100%;
  height: auto;
  background: var(--bg);
  border: 1px solid var(--line-soft);
  border-radius: 2px;
}

.sq-controls {
  display: flex;
  gap: 8px;
  flex-wrap: wrap;
  margin-top: 18px;
  padding-top: 18px;
  border-top: 1px dashed var(--line);
}
.sq-btn {
  font-family: var(--serif-cn);
  font-size: 14px;
  padding: 8px 16px;
  background: white;
  color: var(--ink);
  border: 1px solid var(--line);
  border-radius: 2px;
  cursor: pointer;
  letter-spacing: 0.04em;
  transition: all .15s;
}
.sq-btn:hover {
  border-color: var(--ink);
  background: var(--bg-soft);
}
.sq-btn.primary {
  background: var(--ink);
  color: var(--bg);
  border-color: var(--ink);
}
.sq-btn.primary:hover {
  background: var(--accent);
  border-color: var(--accent);
}
.sq-btn.active {
  background: var(--accent);
  color: var(--bg);
  border-color: var(--accent);
}
.sq-btn .en {
  display: block;
  font-size: 11px;
  letter-spacing: 0.18em;
  color: inherit;
  opacity: 0.7;
  margin-top: 1px;
  font-style: normal;
}

/* ===== 子模块标题（SD 专题 / 综合 等） ===== */
.sq-subhead {
  font-family: var(--display);
  font-size: 12.5px;
  letter-spacing: 0.3em;
  color: var(--gold);
  text-transform: uppercase;
  text-align: center;
  margin: 8px 0 18px;
  padding-bottom: 10px;
  border-bottom: 1px solid var(--line-soft);
}
.sq-subhead.has-margin-top { margin-top: 36px; }

/* ===== SD 专题：表 + 公式 ===== */
.sd-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 28px;
  margin-top: 18px;
  align-items: start;
}
@media (max-width: 720px) {
  .sd-grid { grid-template-columns: 1fr; }
}
.sd-table {
  width: 100%;
  border-collapse: collapse;
  font-family: var(--serif-en);
  font-size: 14px;
}
.sd-table th, .sd-table td {
  text-align: right;
  padding: 5px 10px;
  border-bottom: 1px solid var(--line-soft);
}
.sd-table th:first-child, .sd-table td:first-child {
  text-align: left;
  color: var(--muted);
  font-style: italic;
}
.sd-table thead th {
  font-family: var(--display);
  font-size: 10.5px;
  letter-spacing: 0.18em;
  color: var(--muted);
  text-transform: uppercase;
  border-bottom: 1px solid var(--line);
  font-weight: 500;
}
.sd-table tfoot td {
  border-top: 1px solid var(--line);
  border-bottom: none;
  padding-top: 8px;
  font-weight: 600;
  color: var(--accent);
}
.sd-formula {
  background: var(--bg);
  border: 1px solid var(--line-soft);
  border-radius: 2px;
  padding: 18px 16px;
  font-size: 16px;
  overflow-x: auto;
}
.sd-formula .katex-display {
  margin: 0.6em 0;
}
.sd-formula .katex-display:first-child { margin-top: 0; }
.sd-formula .katex-display:last-child { margin-bottom: 0; }

/* ===== 题目 quiz ===== */
.sq-quiz {
  background: white;
  border: 1px solid var(--line);
  border-radius: 4px;
  padding: 28px 30px;
}
.sq-question {
  margin-bottom: 28px;
  padding-bottom: 22px;
  border-bottom: 1px dashed var(--line-soft);
}
.sq-question:last-child { border-bottom: none; margin-bottom: 0; padding-bottom: 0; }
.sq-question .q-num {
  font-family: var(--display);
  font-size: 11px;
  letter-spacing: 0.24em;
  color: var(--gold);
  text-transform: uppercase;
  margin-bottom: 8px;
}
.sq-question .q-text {
  font-size: 17.5px;
  line-height: 1.8;
  color: var(--ink);
  margin-bottom: 14px;
}
.sq-options {
  display: flex;
  flex-direction: column;
  gap: 8px;
}
.sq-option {
  padding: 13px 18px;
  border: 1px solid var(--line);
  background: var(--bg);
  border-radius: 2px;
  cursor: pointer;
  font-family: var(--serif-cn);
  font-size: 16.5px;
  color: var(--ink-soft);
  text-align: left;
  transition: all .15s;
}
.sq-option:hover:not(:disabled) {
  border-color: var(--ink);
  background: white;
}
.sq-option:disabled { cursor: default; }
.sq-option.correct {
  background: var(--quiz-correct-soft);
  border-color: var(--quiz-correct);
  color: var(--quiz-correct);
}
.sq-option.wrong {
  background: var(--quiz-wrong-soft);
  border-color: var(--quiz-wrong);
  color: var(--quiz-wrong);
}
.sq-feedback {
  margin-top: 12px;
  padding: 10px 14px;
  font-size: 14px;
  font-style: italic;
  border-radius: 2px;
}
.sq-feedback.correct {
  background: var(--quiz-correct-soft);
  color: var(--quiz-correct);
}
.sq-feedback.wrong {
  background: var(--quiz-wrong-soft);
  color: var(--quiz-wrong);
}

/* ===== 底部导航 ===== */
.sq-level-nav {
  display: flex;
  justify-content: space-between;
  margin-top: 60px;
  padding-top: 28px;
  border-top: 1px solid var(--line-soft);
}
.sq-level-nav a {
  font-family: var(--display);
  font-size: 12.5px;
  letter-spacing: 0.22em;
  color: var(--muted);
  text-transform: uppercase;
}
.sq-level-nav a:hover { color: var(--ink); border-bottom: 1px solid var(--ink); }
.sq-level-nav a.next.locked {
  color: var(--line);
  cursor: not-allowed;
  pointer-events: none;
}

/* ===== 主页（关卡选择） ===== */
.sq-home {
  max-width: 960px;
  margin: 0 auto;
  padding: 64px 32px 100px;
}
.sq-home-hero {
  text-align: center;
  margin-bottom: 56px;
}
.sq-home-hero .label {
  font-family: var(--display);
  font-size: 12px;
  letter-spacing: 0.32em;
  color: var(--gold);
  text-transform: uppercase;
  margin-bottom: 14px;
}
.sq-home-hero h1 {
  font-family: var(--serif-cn);
  font-size: 36px;
  font-weight: 500;
  letter-spacing: 0.04em;
  margin-bottom: 12px;
}
.sq-home-hero .en-title {
  font-family: var(--display);
  font-size: 15px;
  letter-spacing: 0.28em;
  color: var(--muted);
}
.sq-home-hero .intro {
  max-width: 600px;
  margin: 28px auto 0;
  color: var(--ink-soft);
  font-size: 16.5px;
  line-height: 1.9;
}

/* 主页通关进度条 */
.sq-progress-card {
  background: white;
  border: 1px solid var(--line);
  padding: 22px 26px;
  margin: 0 0 36px;
}
.sq-progress-head {
  display: flex;
  justify-content: space-between;
  align-items: baseline;
  margin-bottom: 14px;
}
.sq-progress-title {
  font-family: var(--display);
  font-size: 12.5px;
  letter-spacing: 0.28em;
  color: var(--gold);
  text-transform: uppercase;
  font-weight: 500;
}
.sq-progress-stat {
  font-family: var(--serif-en);
  font-style: italic;
  font-size: 14px;
  color: var(--muted);
}
.sq-progress-bar {
  height: 6px;
  background: var(--bg-soft);
  border: 1px solid var(--line-soft);
  border-radius: 1px;
  overflow: hidden;
}
.sq-progress-fill {
  height: 100%;
  background: var(--quiz-correct);
  transition: width 0.3s ease;
}
.sq-progress-reset {
  font-family: var(--serif-en);
  font-style: italic;
  font-size: 12.5px;
  color: var(--muted);
  margin-top: 12px;
  text-align: right;
}
.sq-progress-reset a {
  color: var(--muted);
  border-bottom: 1px dotted var(--line);
  text-decoration: none;
  cursor: pointer;
}
.sq-progress-reset a:hover {
  color: var(--accent);
  border-bottom-color: var(--accent);
}

.sq-level-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 22px;
}
@media (max-width: 720px) {
  .sq-level-grid { grid-template-columns: 1fr; }
}

.sq-level-card {
  background: white;
  border: 1px solid var(--line);
  border-radius: 4px;
  padding: 24px 26px;
  display: block;
  transition: transform .2s, box-shadow .2s, border-color .2s;
  position: relative;
}
.sq-level-card:hover:not(.locked) {
  transform: translateY(-2px);
  box-shadow: 0 8px 20px rgba(0,0,0,0.05);
  border-color: var(--ink);
}
.sq-level-card.locked {
  background: var(--bg-soft);
  cursor: not-allowed;
  opacity: 0.55;
}
.sq-level-card.completed {
  border-color: var(--quiz-correct);
}
.sq-level-card .num {
  font-family: var(--display);
  font-size: 11px;
  letter-spacing: 0.32em;
  color: var(--gold);
  text-transform: uppercase;
  margin-bottom: 8px;
}
.sq-level-card .num.locked { color: var(--muted); }
.sq-level-card .num.completed { color: var(--quiz-correct); }
.sq-level-card h3 {
  font-family: var(--serif-cn);
  font-size: 18.5px;
  font-weight: 500;
  letter-spacing: 0.02em;
  color: var(--ink);
  margin-bottom: 4px;
}
.sq-level-card .en-sub {
  font-family: var(--display);
  font-size: 12px;
  letter-spacing: 0.22em;
  color: var(--muted);
  margin-bottom: 12px;
  text-transform: uppercase;
}
.sq-level-card .summary {
  font-size: 14.5px;
  line-height: 1.75;
  color: var(--ink-soft);
}
.sq-level-card .status {
  position: absolute;
  top: 18px;
  right: 22px;
  font-family: var(--display);
  font-size: 10.5px;
  letter-spacing: 0.22em;
  color: var(--muted);
  text-transform: uppercase;
}
.sq-level-card.completed .status { color: var(--quiz-correct); }