/* ============================================================
   编程启蒙学堂 — 样式表（浅色主题 / 清爽 / 初学者友好）
   ============================================================ */

:root {
  --bg: #f5f7fa;
  --surface: #ffffff;
  --surface-2: #f0f4f8;
  --border: #e2e8f0;
  --text: #1f2a37;
  --text-soft: #5b6b7b;
  --primary: #2f6fdb;
  --primary-soft: #e8f0fe;
  --primary-dark: #1f54b0;
  --accent: #0d9488;
  --warn: #d97706;
  --danger: #dc2626;
  --ok: #16a34a;
  --code-bg: #1e293b;
  --code-text: #e2e8f0;
  --shadow: 0 1px 3px rgba(15, 23, 42, .08), 0 6px 18px rgba(15, 23, 42, .06);
  --radius: 14px;
  --radius-sm: 9px;
  --sidebar-w: 280px;
  --topbar-h: 60px;
  --maxw: 980px;
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC",
    "Hiragino Sans GB", "Microsoft YaHei", "Helvetica Neue", Arial, sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.75;
  font-size: 16px;
  -webkit-font-smoothing: antialiased;
}

/* ---------- 顶栏 ---------- */
.topbar {
  position: sticky; top: 0; z-index: 50;
  height: var(--topbar-h);
  display: flex; align-items: center; gap: 14px;
  padding: 0 18px;
  background: var(--surface);
  border-bottom: 1px solid var(--border);
  box-shadow: var(--shadow);
}
.brand { display: flex; align-items: center; gap: 9px; text-decoration: none; color: var(--text); font-weight: 700; font-size: 18px; }
.brand-logo { font-size: 22px; }
.brand-name { letter-spacing: .5px; }
.menu-toggle {
  display: none; border: none; background: transparent; font-size: 22px;
  cursor: pointer; color: var(--text); padding: 4px 8px; border-radius: 8px;
}
.menu-toggle:hover { background: var(--surface-2); }
.topnav { display: flex; gap: 4px; margin-left: 8px; flex-wrap: wrap; }
.topnav a {
  text-decoration: none; color: var(--text-soft); font-size: 14px;
  padding: 7px 13px; border-radius: 999px; transition: .15s; white-space: nowrap;
}
.topnav a:hover { background: var(--surface-2); color: var(--text); }
.topnav a.active { background: var(--primary-soft); color: var(--primary-dark); font-weight: 600; }
.progress-pill {
  margin-left: auto; background: var(--surface-2); color: var(--text-soft);
  font-size: 13px; padding: 6px 14px; border-radius: 999px; border: 1px solid var(--border);
  white-space: nowrap;
}

/* ---------- 布局 ---------- */
.layout { display: flex; align-items: flex-start; }
.sidebar {
  width: var(--sidebar-w); flex: 0 0 var(--sidebar-w);
  height: calc(100vh - var(--topbar-h));
  position: sticky; top: var(--topbar-h);
  background: var(--surface);
  border-right: 1px solid var(--border);
  overflow: hidden;
}
.sidebar-scroll { height: 100%; overflow-y: auto; padding: 14px 10px 40px; }
.content { flex: 1 1 auto; min-width: 0; padding: 30px 34px 90px; }
.content-inner { max-width: var(--maxw); margin: 0 auto; }

/* ---------- 侧边栏导航 ---------- */
.nav-module { margin-bottom: 6px; }
.nav-module > .nav-module-head {
  display: flex; align-items: center; gap: 9px;
  padding: 9px 11px; border-radius: var(--radius-sm); cursor: pointer;
  font-weight: 600; color: var(--text); user-select: none;
}
.nav-module > .nav-module-head:hover { background: var(--surface-2); }
.nav-module-head .nm-icon { font-size: 18px; }
.nav-module-head .nm-title { flex: 1; font-size: 14.5px; }
.nav-module-head .nm-caret { transition: transform .2s; color: var(--text-soft); font-size: 12px; }
.nav-module.open > .nav-module-head .nm-caret { transform: rotate(90deg); }
.nav-chapters { list-style: none; margin: 2px 0 4px; padding: 0 0 0 14px; display: none; }
.nav-module.open .nav-chapters { display: block; }
/* 侧边栏阶段分组小标题 */
.nav-stage { display: none; align-items: center; gap: 7px; margin: 8px 0 2px; padding: 0 10px 0 8px; }
.nav-module.open .nav-stage { display: flex; }
.nav-stage .ns-text { font-size: 11.5px; color: var(--text-soft); letter-spacing: .5px; }
.nav-chapters li a {
  display: flex; align-items: center; gap: 8px;
  text-decoration: none; color: var(--text-soft); font-size: 13.5px;
  padding: 7px 10px; border-radius: 8px; transition: .12s;
}
.nav-chapters li a:hover { background: var(--surface-2); color: var(--text); }
.nav-chapters li a.active { background: var(--primary-soft); color: var(--primary-dark); font-weight: 600; }
.nav-chapters li a .ch-idx { font-size: 11px; opacity: .7; }
.nav-chapters li a .ch-done { margin-left: auto; color: var(--ok); font-size: 12px; opacity: 0; }
.nav-chapters li a.done .ch-done { opacity: 1; }

/* ---------- 首页 ---------- */
.hero {
  background: linear-gradient(135deg, #2f6fdb 0%, #0d9488 100%);
  color: #fff; border-radius: var(--radius);
  padding: 44px 40px; margin-bottom: 30px; box-shadow: var(--shadow);
}
.hero h1 { margin: 0 0 10px; font-size: 32px; }
.hero p { margin: 0 0 6px; opacity: .94; max-width: 640px; }
.hero .hero-tags { margin-top: 16px; display: flex; gap: 8px; flex-wrap: wrap; }
.hero .hero-tags span {
  background: rgba(255,255,255,.18); padding: 5px 13px; border-radius: 999px; font-size: 13px;
}
.home-section-title { font-size: 20px; margin: 30px 0 14px; display: flex; align-items: center; gap: 8px; }
.module-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(260px, 1fr)); gap: 18px; }
.module-card {
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 22px; text-decoration: none; color: var(--text); box-shadow: var(--shadow);
  transition: transform .15s, box-shadow .15s; display: block;
}
.module-card:hover { transform: translateY(-3px); box-shadow: 0 10px 28px rgba(15,23,42,.12); }
.module-card .mc-icon { font-size: 34px; }
.module-card .mc-title { font-size: 18px; font-weight: 700; margin: 10px 0 6px; }
.module-card .mc-desc { color: var(--text-soft); font-size: 14px; min-height: 42px; }
.module-card .mc-meta { margin-top: 14px; font-size: 12.5px; color: var(--text-soft); display: flex; gap: 12px; }
.module-card .mc-meta b { color: var(--primary-dark); }

.home-features { display: grid; grid-template-columns: repeat(auto-fill, minmax(220px, 1fr)); gap: 16px; margin-top: 8px; }
.feature-box { background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius); padding: 18px; box-shadow: var(--shadow); }
.feature-box .fb-icon { font-size: 24px; }
.feature-box h3 { margin: 8px 0 4px; font-size: 15px; }
.feature-box p { margin: 0; color: var(--text-soft); font-size: 13.5px; }

/* ---------- 模块总览页 ---------- */
.module-head-banner {
  display: flex; align-items: center; gap: 16px; margin-bottom: 22px;
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 22px 26px; box-shadow: var(--shadow);
}
.module-head-banner .mhb-icon { font-size: 44px; }
.module-head-banner h1 { margin: 0 0 4px; font-size: 24px; }
.module-head-banner p { margin: 0; color: var(--text-soft); }
.chapter-list { display: grid; grid-template-columns: repeat(auto-fill, minmax(280px, 1fr)); gap: 14px; }
.chapter-card {
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius-sm);
  padding: 16px 18px; text-decoration: none; color: var(--text); box-shadow: var(--shadow); transition: .15s;
  display: flex; gap: 12px; align-items: flex-start;
}
.chapter-card:hover { transform: translateY(-2px); border-color: var(--primary); }
.chapter-card .cc-num {
  flex: 0 0 34px; height: 34px; border-radius: 9px; background: var(--primary-soft); color: var(--primary-dark);
  display: flex; align-items: center; justify-content: center; font-weight: 700; font-size: 15px;
}
.chapter-card .cc-body .cc-title { font-weight: 600; }
.chapter-card .cc-body .cc-desc { color: var(--text-soft); font-size: 13px; margin-top: 2px; }

/* ---------- 章节内容 ---------- */
.breadcrumb { font-size: 13px; color: var(--text-soft); margin-bottom: 14px; }
.breadcrumb a { color: var(--text-soft); text-decoration: none; }
.breadcrumb a:hover { color: var(--primary); }
.chapter-title { font-size: 26px; margin: 0 0 6px; }
.chapter-sub { color: var(--text-soft); margin: 0 0 22px; }

.section { margin: 22px 0; }
.section h2 { font-size: 20px; margin: 0 0 10px; padding-left: 11px; border-left: 4px solid var(--primary); }
.section p { margin: 10px 0; }
.section ul, .section ol { margin: 10px 0; padding-left: 24px; }
.section li { margin: 5px 0; }
.section code.inline {
  background: var(--surface-2); border: 1px solid var(--border); border-radius: 5px;
  padding: 1px 6px; font-family: "SFMono-Regular", Consolas, "Liberation Mono", monospace; font-size: 14px; color: #b1356b;
}
.tip, .warn-box, .note {
  border-radius: var(--radius-sm); padding: 12px 16px; margin: 14px 0; font-size: 14.5px;
  border: 1px solid; display: flex; gap: 10px;
}
.tip { background: #ecfdf5; border-color: #a7f3d0; color: #065f46; }
.warn-box { background: #fffbeb; border-color: #fde68a; color: #92400e; }
.note { background: var(--primary-soft); border-color: #bfdbfe; color: #1e40af; }
.tip::before { content: "💡"; }
.warn-box::before { content: "⚠️"; }
.note::before { content: "📌"; }

/* ---------- 代码块 ---------- */
.code-block { margin: 14px 0; border-radius: var(--radius-sm); overflow: hidden; border: 1px solid #0f172a; background: var(--code-bg); }
.code-head {
  display: flex; align-items: center; gap: 8px; padding: 7px 12px;
  background: #0b1220; color: #94a3b8; font-size: 12.5px; border-bottom: 1px solid #1e293b;
}
.code-head .ch-lang { font-weight: 600; color: #cbd5e1; }
.code-head .ch-actions { margin-left: auto; display: flex; gap: 6px; }
.code-head button {
  background: #1e293b; color: #cbd5e1; border: 1px solid #334155; border-radius: 6px;
  padding: 3px 10px; font-size: 12px; cursor: pointer; transition: .12s;
}
.code-head button:hover { background: #334155; color: #fff; }
.code-block pre { margin: 0; padding: 14px 16px; overflow-x: auto; }
.code-block code {
  font-family: "SFMono-Regular", Consolas, "Liberation Mono", monospace; font-size: 13.5px;
  line-height: 1.6; color: var(--code-text); white-space: pre;
}
/* 简易语法高亮 */
.tok-key { color: #93c5fd; }
.tok-str { color: #fca5a5; }
.tok-num { color: #fcd34d; }
.tok-com { color: #64748b; font-style: italic; }
.tok-fn  { color: #6ee7b7; }
.tok-punc{ color: #cbd5e1; }

/* 运行结果区 */
.run-output {
  background: #0b1220; color: #e2e8f0; border-top: 1px solid #1e293b;
  padding: 12px 16px; font-family: "SFMono-Regular", Consolas, monospace; font-size: 13px;
  white-space: pre-wrap; min-height: 20px;
}
.run-output .ro-label { color: #64748b; }
.run-output.error { color: #fca5a5; }

/* iframe 实时预览 */
.preview-frame {
  width: 100%; height: 300px; border: 1px solid var(--border); border-radius: var(--radius-sm);
  background: #fff; margin-top: 10px;
}

/* ---------- 练习题 ---------- */
.exercise {
  background: var(--surface); border: 1px solid var(--border); border-left: 4px solid var(--warn);
  border-radius: var(--radius-sm); padding: 16px 20px; margin: 18px 0; box-shadow: var(--shadow);
}
.exercise h3 { margin: 0 0 8px; font-size: 16px; color: #92400e; }
.exercise .ex-q { margin: 0 0 10px; }
.exercise details { margin-top: 10px; }
.exercise summary { cursor: pointer; color: var(--primary-dark); font-size: 14px; font-weight: 600; }
.exercise details[open] summary { margin-bottom: 8px; }
.exercise .ex-answer { color: var(--text-soft); font-size: 14px; }
.exercise .ex-answer pre { background: var(--code-bg); color: var(--code-text); padding: 12px; border-radius: 8px; overflow-x: auto; }

/* ---------- 自测题 ---------- */
.quiz {
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 20px 24px; margin: 22px 0; box-shadow: var(--shadow);
}
.quiz h3 { margin: 0 0 4px; font-size: 17px; display: flex; align-items: center; gap: 8px; }
.quiz .quiz-sub { color: var(--text-soft); font-size: 13.5px; margin: 0 0 14px; }
.quiz-q { margin: 16px 0; padding: 14px 16px; border: 1px solid var(--border); border-radius: var(--radius-sm); background: var(--surface-2); }
.quiz-q .qq-text { font-weight: 600; margin-bottom: 10px; }
.quiz-q .qq-text .qq-num { color: var(--primary); margin-right: 6px; }
.quiz-opt {
  display: block; padding: 9px 13px; margin: 6px 0; border: 1px solid var(--border);
  border-radius: 8px; cursor: pointer; transition: .12s; background: var(--surface); font-size: 14.5px;
}
.quiz-opt:hover { border-color: var(--primary); }
.quiz-opt.selected { border-color: var(--primary); background: var(--primary-soft); }
.quiz-opt.correct { border-color: var(--ok); background: #ecfdf5; }
.quiz-opt.wrong { border-color: var(--danger); background: #fef2f2; }
.quiz-opt .opt-key { font-weight: 700; margin-right: 8px; display: inline-block; width: 18px; }
.quiz-feedback { font-size: 13.5px; margin-top: 8px; }
.quiz-feedback.ok { color: var(--ok); }
.quiz-feedback.bad { color: var(--danger); }
.quiz-submit {
  margin-top: 16px; background: var(--primary); color: #fff; border: none; border-radius: 9px;
  padding: 10px 22px; font-size: 15px; font-weight: 600; cursor: pointer; transition: .15s;
}
.quiz-submit:hover { background: var(--primary-dark); }
.quiz-result { margin-top: 14px; font-size: 15px; font-weight: 700; padding: 12px 16px; border-radius: var(--radius-sm); display: none; }
.quiz-result.show { display: block; }
.quiz-result.pass { background: #ecfdf5; color: #065f46; border: 1px solid #a7f3d0; }
.quiz-result.fail { background: #fffbeb; color: #92400e; border: 1px solid #fde68a; }

/* ---------- 多题型测试 ---------- */
.quiz-types { display: flex; flex-wrap: wrap; gap: 6px; margin-bottom: 14px; }
.qt-chip {
  display: inline-block; font-size: 12px; font-weight: 600; line-height: 1.6;
  padding: 2px 9px; border-radius: 999px; background: var(--primary-soft); color: var(--primary-dark);
  border: 1px solid rgba(0, 0, 0, .06); white-space: nowrap;
}
.quiz-q .qq-head { display: flex; align-items: center; gap: 8px; margin-bottom: 6px; }
.quiz-q .qq-head .qq-num { color: var(--primary); font-weight: 700; }
.quiz-q[data-qt="choice"] .qt-chip, .quiz-q[data-qt="multi"] .qt-chip { background: #eef2ff; color: #3730a3; }
.quiz-q[data-qt="fill"] .qt-chip { background: #ecfeff; color: #0e7490; }
.quiz-q[data-qt="judge"] .qt-chip { background: #fef3c7; color: #92400e; }
.quiz-q[data-qt="short"] .qt-chip { background: #fce7f3; color: #9d174d; }
.quiz-q[data-qt="task"] .qt-chip { background: #dcfce7; color: #166534; }

/* 知识点标签 */
.qq-kp { margin: 6px 0 10px; display: flex; flex-wrap: wrap; align-items: center; gap: 5px; }
.qq-kp-label { font-size: 12px; color: var(--text-soft); margin-right: 2px; }
.kp-tag {
  font-size: 11.5px; line-height: 1.6; padding: 1px 8px; border-radius: 4px;
  background: var(--surface-2); color: var(--text-soft); border: 1px dashed var(--border);
}
.quiz-q .quiz-tip { font-size: 12.5px; color: var(--text-soft); margin-top: 6px; }

/* 判断题 */
.judge-row { display: flex; gap: 10px; flex-wrap: wrap; }
.judge-row .quiz-opt { display: inline-flex; align-items: center; min-width: 96px; }
.judge-row .opt-key { font-weight: 700; }

/* 填空题 / 主观题 输入控件 */
.quiz-input, .quiz-textarea {
  width: 100%; box-sizing: border-box; font-family: inherit; font-size: 14px; color: var(--text);
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius-sm);
  padding: 9px 12px; margin-top: 4px;
}
.quiz-input:focus, .quiz-textarea:focus { outline: none; border-color: var(--primary); box-shadow: 0 0 0 3px var(--primary-soft); }
.quiz-textarea { resize: vertical; line-height: 1.7; font-family: ui-monospace, SFMono-Regular, Consolas, monospace; font-size: 13.5px; }
.quiz-reveal { margin-left: 10px; }
.quiz-feedback.info { color: var(--primary-dark); }

/* ---------- 答案卷 ---------- */
.answer-sheet {
  margin: 18px 0; padding: 18px 20px; border: 1px solid var(--border);
  border-radius: var(--radius-sm); background: var(--surface-2);
}
.answer-sheet h3 { margin: 0 0 4px; font-size: 17px; display: flex; align-items: center; gap: 8px; }
.as-item { padding: 12px 0; border-bottom: 1px dashed var(--border); }
.as-item:last-child { border-bottom: none; }
.as-head { display: flex; align-items: flex-start; gap: 8px; flex-wrap: wrap; margin-bottom: 4px; }
.as-head .qq-num { color: var(--primary); font-weight: 700; }
.as-head .as-q { flex: 1; min-width: 240px; font-weight: 600; }
.as-kp { font-size: 12px; color: var(--text-soft); margin-bottom: 4px; }
.as-answer { font-size: 13.5px; color: var(--ok); font-weight: 600; }
.as-explain { font-size: 13.5px; color: var(--text-soft); line-height: 1.75; margin-top: 2px; }

/* ---------- 章节小结 ---------- */
.chapter-summary {
  margin: 18px 0; padding: 16px 18px; border-left: 4px solid var(--primary);
  border-radius: var(--radius-sm); background: var(--primary-soft);
}
.chapter-summary h3 { margin: 0 0 8px; font-size: 16px; display: flex; align-items: center; gap: 8px; }
.chapter-summary ul { margin: 0; padding-left: 20px; }
.chapter-summary li { margin-bottom: 6px; line-height: 1.8; }
.chapter-summary li:last-child { margin-bottom: 0; }

/* ---------- 上/下章导航 ---------- */
.chapter-nav { display: flex; justify-content: space-between; gap: 12px; margin-top: 36px; }
.chapter-nav a {
  text-decoration: none; color: var(--primary-dark); border: 1px solid var(--border);
  background: var(--surface); border-radius: var(--radius-sm); padding: 12px 18px; box-shadow: var(--shadow);
  flex: 1; max-width: 48%; transition: .15s;
}
.chapter-nav a:hover { border-color: var(--primary); }
.chapter-nav a.disabled { opacity: .4; pointer-events: none; }
.chapter-nav .cn-dir { font-size: 12px; color: var(--text-soft); }
.chapter-nav .cn-title { font-weight: 600; }
.chapter-nav .next { text-align: right; }

/* 完成按钮 */
.mark-done {
  display: inline-flex; align-items: center; gap: 7px; margin-top: 8px;
  background: var(--surface); border: 1px solid var(--border); border-radius: 999px;
  padding: 8px 16px; font-size: 14px; cursor: pointer; color: var(--text-soft); transition: .15s;
}
.mark-done:hover { border-color: var(--ok); color: var(--ok); }
.mark-done.done { background: #ecfdf5; border-color: #a7f3d0; color: var(--ok); font-weight: 600; }

/* ============================================================
   阶段体系：难度徽章 / 阶段卡片 / 学习目标 / 学习路线图
   ============================================================ */
.level-badge {
  display: inline-flex; align-items: center; font-size: 12px; font-weight: 700;
  padding: 2px 10px; border-radius: 999px; border: 1px solid transparent; white-space: nowrap;
}
.level-badge.lv-1 { background: #ecfdf5; color: #047857; border-color: #a7f3d0; }
.level-badge.lv-2 { background: #eff6ff; color: #1d4ed8; border-color: #bfdbfe; }
.level-badge.lv-3 { background: #fef2f2; color: #b91c1c; border-color: #fecaca; }

/* 首页路线图 */
.roadmap { display: grid; grid-template-columns: repeat(auto-fit, minmax(260px, 1fr)); gap: 16px; }
.roadmap-step {
  background: var(--surface); border: 1px solid var(--border); border-top: 4px solid var(--primary);
  border-radius: var(--radius); padding: 18px 20px; box-shadow: var(--shadow);
}
.roadmap-step.lv-1 { border-top-color: #10b981; }
.roadmap-step.lv-2 { border-top-color: #3b82f6; }
.roadmap-step.lv-3 { border-top-color: #ef4444; }
.roadmap-step .rs-head { display: flex; align-items: center; gap: 9px; flex-wrap: wrap; }
.roadmap-step .rs-num {
  width: 26px; height: 26px; border-radius: 50%; background: var(--primary-soft); color: var(--primary-dark);
  display: inline-flex; align-items: center; justify-content: center; font-weight: 700; font-size: 14px;
}
.roadmap-step .rs-title { font-weight: 700; font-size: 15.5px; }
.roadmap-step .rs-desc { color: var(--text-soft); font-size: 13.5px; margin: 10px 0 8px; }
.roadmap-step .rs-outcome { font-size: 13px; color: var(--text); background: var(--surface-2); border-radius: 8px; padding: 8px 11px; }
.roadmap-step .rs-o-label { color: var(--text-soft); font-weight: 600; }

/* 模块总览摘要条 */
.module-summary { display: flex; gap: 18px; flex-wrap: wrap; margin: 0 0 6px; font-size: 13.5px; color: var(--text-soft); }
.module-summary b { color: var(--primary-dark); font-size: 15px; }

/* 模块总览：阶段卡片 */
.stage-card {
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 20px 22px; margin: 18px 0; box-shadow: var(--shadow); border-left: 5px solid var(--primary);
}
.stage-card.lv-1 { border-left-color: #10b981; }
.stage-card.lv-2 { border-left-color: #3b82f6; }
.stage-card.lv-3 { border-left-color: #ef4444; }
.stage-head { display: flex; align-items: center; gap: 10px; flex-wrap: wrap; margin-bottom: 12px; }
.stage-head .stage-index { font-size: 13px; font-weight: 700; color: var(--text-soft); letter-spacing: .5px; }
.stage-head .stage-title { font-size: 18px; font-weight: 700; }
.stage-specs { display: grid; grid-template-columns: 1fr 1fr; gap: 14px; margin: 0 0 16px; }
.stage-specs .spec, .obj-box .spec {
  background: var(--surface-2); border: 1px solid var(--border); border-radius: var(--radius-sm); padding: 12px 15px;
}
.spec .spec-label { font-size: 13.5px; font-weight: 700; margin-bottom: 4px; }
.spec.goal .spec-label { color: #047857; }
.spec.points .spec-label { color: #b45309; }
.spec ul { margin: 4px 0 0; padding-left: 20px; }
.spec li { font-size: 13.5px; margin: 3px 0; color: var(--text); }

/* 章节页：阶段信息与目标框 */
.chapter-meta { display: flex; align-items: center; gap: 10px; flex-wrap: wrap; margin: 0 0 6px; font-size: 13px; color: var(--text-soft); }
.chapter-meta .cm-stage { font-weight: 600; color: var(--primary-dark); }
.obj-box {
  background: linear-gradient(180deg, #f8fafc, #fff); border: 1px dashed var(--border);
  border-radius: var(--radius); padding: 16px 18px; margin: 4px 0 20px;
  display: grid; grid-template-columns: 1fr 1fr; gap: 14px;
}
.goal-box { background: #ecfdf5; border: 1px solid #a7f3d0; border-radius: var(--radius-sm); padding: 12px 16px; margin: 14px 0; color: #065f46; }

/* ============================================================
   大型项目与答疑区样式
   ============================================================ */

/* 项目卡片 */
.project-card {
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 22px 24px; margin: 22px 0; box-shadow: var(--shadow); border-top: 4px solid var(--primary);
}
.project-card .pc-head { display: flex; align-items: center; gap: 12px; margin-bottom: 14px; }
.project-card .pc-icon { font-size: 28px; }
.project-card .pc-title { font-size: 20px; font-weight: 700; color: var(--primary-dark); }
.project-card .pc-desc { color: var(--text-soft); line-height: 1.7; margin-bottom: 16px; }
.project-card .pc-section { margin-top: 14px; }
.project-card .pc-label { font-weight: 700; color: var(--text); margin-bottom: 8px; }
.project-card .pc-list { padding-left: 18px; color: var(--text-soft); line-height: 1.8; }
.project-card .pc-list li { margin-bottom: 4px; }
.project-card .pc-tags { display: flex; flex-wrap: wrap; gap: 8px; }
.project-card .pc-tag {
  background: var(--primary-soft); color: var(--primary-dark); font-size: 13px;
  padding: 5px 12px; border-radius: 999px; border: 1px solid var(--border);
}

/* 项目文件结构树 */
.project-structure {
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 22px 24px; margin: 22px 0; box-shadow: var(--shadow);
}
.project-structure .ps-head { display: flex; align-items: center; gap: 10px; margin-bottom: 12px; }
.project-structure .ps-icon { font-size: 22px; }
.project-structure .ps-title { font-size: 18px; font-weight: 700; color: var(--text); }
.project-structure .ps-desc { color: var(--text-soft); margin-bottom: 14px; line-height: 1.6; }
.file-tree { background: var(--surface-2); border-radius: var(--radius-sm); padding: 14px 18px; font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace; font-size: 14px; }
.ft-row { display: flex; align-items: center; gap: 8px; padding: 5px 0; border-bottom: 1px dashed var(--border); }
.ft-row:last-child { border-bottom: none; }
.ft-name { color: var(--text); font-weight: 500; min-width: 180px; }
.ft-desc { color: var(--text-soft); font-size: 13px; }

/* 项目实现步骤 */
.project-step {
  background: var(--surface); border: 1px solid var(--border); border-left: 4px solid var(--primary);
  border-radius: var(--radius); padding: 20px 24px; margin: 22px 0; box-shadow: var(--shadow);
}
.project-step .pst-head { display: flex; align-items: center; gap: 12px; margin-bottom: 12px; flex-wrap: wrap; }
.project-step .pst-num {
  background: var(--primary); color: #fff; font-size: 13px; font-weight: 700;
  padding: 4px 10px; border-radius: var(--radius-sm);
}
.project-step .pst-title { font-size: 18px; font-weight: 700; color: var(--text); }
.project-step .pst-goal { background: #ecfdf5; border: 1px solid #a7f3d0; border-radius: var(--radius-sm); padding: 10px 14px; color: #065f46; margin-bottom: 14px; }
.project-step .pst-body { color: var(--text-soft); line-height: 1.8; margin-bottom: 14px; }
.project-step .pst-points { background: #fffbeb; border: 1px solid #fde68a; border-radius: var(--radius-sm); padding: 12px 16px; }
.project-step .pst-plabel { font-weight: 700; color: #92400e; margin-bottom: 6px; }
.project-step .pst-points ul { padding-left: 18px; color: #78350f; line-height: 1.7; margin: 0; }
.project-step .code-block { margin: 14px 0 0; }

/* 概念解释框 */
.explain-box {
  background: var(--surface-2); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 18px 20px; margin: 20px 0;
}
.explain-box .eb-head { display: flex; align-items: center; gap: 10px; margin-bottom: 10px; }
.explain-box .eb-icon { font-size: 20px; }
.explain-box .eb-title { font-size: 16px; font-weight: 700; color: var(--text); }
.explain-box .eb-body { color: var(--text-soft); line-height: 1.8; }
.explain-box .eb-common { margin-top: 12px; padding: 10px 14px; background: #fff1f2; border: 1px solid #fecdd3; border-radius: var(--radius-sm); color: #9f1239; font-size: 14px; line-height: 1.6; }
.explain-box .eb-ask {
  margin-top: 12px; background: var(--surface); border: 1px solid var(--border); color: var(--text-soft);
  padding: 8px 14px; border-radius: var(--radius-sm); cursor: pointer; font-size: 13px;
  transition: all .2s;
}
.explain-box .eb-ask:hover { background: var(--primary-soft); color: var(--primary-dark); border-color: var(--primary); }

/* 答疑区 */
.qa-box { margin: 28px 0; padding: 22px 24px; background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius); box-shadow: var(--shadow); }
.qa-box .qa-head { display: flex; align-items: center; gap: 10px; margin-bottom: 10px; }
.qa-box .qa-icon { font-size: 22px; }
.qa-box .qa-title { font-size: 18px; font-weight: 700; color: var(--primary-dark); }
.qa-box .qa-desc { color: var(--text-soft); margin-bottom: 16px; line-height: 1.6; }
.qa-box .qa-faq { margin-bottom: 18px; }
.qa-box .qa-faq-title { font-weight: 700; color: var(--text); margin-bottom: 10px; }
.qa-faq-item { margin-bottom: 10px; border: 1px solid var(--border); border-radius: var(--radius-sm); overflow: hidden; }
.qa-faq-item summary {
  padding: 12px 14px; background: var(--surface-2); cursor: pointer; font-weight: 600; color: var(--text);
  list-style: none; display: flex; justify-content: space-between; align-items: center;
}
.qa-faq-item summary::-webkit-details-marker { display: none; }
.qa-faq-item summary::after { content: "▶"; font-size: 12px; color: var(--text-soft); transition: transform .2s; }
.qa-faq-item[open] summary::after { transform: rotate(90deg); }
.qa-faq-a { padding: 14px; color: var(--text-soft); line-height: 1.7; background: var(--surface); }
.qa-input-wrap { display: flex; gap: 10px; margin-bottom: 16px; }
.qa-input { flex: 1; padding: 10px 14px; border: 1px solid var(--border); border-radius: var(--radius-sm); font-size: 14px; }
.qa-add { background: var(--primary); color: #fff; border: none; border-radius: var(--radius-sm); padding: 10px 18px; cursor: pointer; font-weight: 600; }
.qa-add:hover { background: var(--primary-dark); }
.qa-empty { color: var(--text-soft); font-size: 14px; }
.qa-items { display: flex; flex-direction: column; gap: 12px; }
.qa-item { background: var(--surface-2); border: 1px solid var(--border); border-radius: var(--radius-sm); padding: 14px; }
.qa-q { display: flex; gap: 10px; color: var(--text); font-weight: 500; line-height: 1.5; }
.qa-dot { background: var(--primary); color: #fff; font-size: 12px; font-weight: 700; width: 22px; height: 22px; border-radius: 50%; display: flex; align-items: center; justify-content: center; flex-shrink: 0; }
.qa-meta { margin-top: 8px; font-size: 12px; color: var(--text-soft); }
.qa-copy { background: transparent; border: none; color: var(--primary); cursor: pointer; text-decoration: underline; padding: 0; font-size: 12px; }

/* ---------- 遮罩与回到顶部 ---------- */
.overlay { position: fixed; inset: 0; background: rgba(15,23,42,.4); z-index: 40; display: none; }
.overlay.show { display: block; }
.to-top {
  position: fixed; right: 24px; bottom: 24px; width: 44px; height: 44px; border-radius: 50%;
  border: none; background: var(--primary); color: #fff; font-size: 20px; cursor: pointer;
  box-shadow: var(--shadow); opacity: 0; pointer-events: none; transition: .2s; z-index: 45;
}
.to-top.show { opacity: 1; pointer-events: auto; }
.to-top:hover { background: var(--primary-dark); }

/* ---------- 技巧与技能信息库 ---------- */
.skill-library { background: #fff; border: 1px solid var(--border); border-radius: 14px; padding: 18px 20px; margin: 18px 0; }
.skill-head { display: flex; justify-content: space-between; align-items: baseline; flex-wrap: wrap; gap: 6px; border-bottom: 1px solid var(--border); padding-bottom: 10px; margin-bottom: 12px; }
.skill-head-title { font-size: 18px; font-weight: 700; color: var(--text); }
.skill-meta { font-size: 13px; color: var(--text-soft); }
.skill-update-banner { background: #fff7ed; border: 1px solid #fed7aa; color: #9a3412; border-radius: 10px; padding: 10px 12px; margin-bottom: 12px; font-size: 14px; display: flex; align-items: center; gap: 10px; flex-wrap: wrap; }
.skill-review-bar { display: flex; align-items: center; gap: 16px; flex-wrap: wrap; background: #f8fafc; border: 1px solid var(--border); border-radius: 10px; padding: 10px 12px; margin-bottom: 14px; font-size: 14px; color: var(--text); }
.skill-review-bar span { color: var(--text-soft); }
.skill-review-bar b { color: var(--primary); }
.mini-btn { border: 1px solid var(--border); background: #fff; color: var(--primary); border-radius: 8px; padding: 5px 12px; font-size: 13px; cursor: pointer; transition: .15s; }
.mini-btn:hover { background: var(--primary); color: #fff; border-color: var(--primary); }
.skill-section-title { font-size: 16px; font-weight: 700; color: var(--text); margin: 18px 0 10px; }
.res-groups { display: grid; grid-template-columns: repeat(auto-fit, minmax(260px, 1fr)); gap: 14px; }
.res-group-title { font-weight: 600; color: var(--primary-dark); margin-bottom: 8px; }
.res-list { display: flex; flex-direction: column; gap: 10px; }
.res-card { display: block; text-decoration: none; background: #f8fafc; border: 1px solid var(--border); border-radius: 10px; padding: 12px 14px; transition: .15s; }
.res-card:hover { border-color: var(--primary); box-shadow: var(--shadow); transform: translateY(-2px); }
.res-name { font-weight: 600; color: var(--text); margin-bottom: 4px; }
.res-desc { font-size: 13px; color: var(--text-soft); line-height: 1.5; }
.res-url { font-size: 12px; color: var(--primary); margin-top: 6px; word-break: break-all; }
.skill-cat { margin-bottom: 14px; }
.skill-cat-title { font-weight: 600; color: var(--primary-dark); margin-bottom: 8px; padding-left: 8px; border-left: 3px solid var(--primary); }
.skill-item { display: flex; gap: 10px; background: #fff; border: 1px solid var(--border); border-radius: 10px; padding: 12px 14px; margin-bottom: 10px; align-items: flex-start; }
.skill-item.mastered { background: #f0fdf4; border-color: #bbf7d0; }
.skill-check { flex: 0 0 auto; margin-top: 2px; cursor: pointer; }
.skill-check input { width: 18px; height: 18px; cursor: pointer; }
.skill-body { flex: 1 1 auto; min-width: 0; }
.skill-name { font-weight: 600; color: var(--text); margin-bottom: 4px; }
.skill-detail { font-size: 14px; color: var(--text-soft); line-height: 1.6; }
.skill-note-wrap { margin-top: 8px; }
.skill-note-input { width: 100%; min-height: 60px; border: 1px solid var(--border); border-radius: 8px; padding: 8px; font-family: inherit; font-size: 14px; resize: vertical; box-sizing: border-box; }
.skill-archive { background: #f8fafc; border: 1px dashed var(--border); border-radius: 10px; padding: 14px; }
.skill-archive-body { margin-top: 10px; }
.archive-stat { font-size: 14px; color: var(--text); margin-bottom: 8px; }
.archive-stat b { color: var(--primary); }
.archive-sub { font-weight: 600; color: var(--text-soft); margin: 8px 0 4px; }
.archive-rev { font-size: 13px; color: var(--text); padding: 3px 0; border-bottom: 1px dashed var(--border); }
.archive-empty { font-size: 13px; color: var(--text-soft); }

/* ---------- 响应式 ---------- */
@media (max-width: 900px) {
  .menu-toggle { display: block; }
  .topnav { display: none; }
  .sidebar {
    position: fixed; left: 0; top: var(--topbar-h); z-index: 45; transform: translateX(-100%);
    transition: transform .25s; box-shadow: var(--shadow);
  }
  .sidebar.open { transform: translateX(0); }
  .content { padding: 22px 16px 80px; }
  .hero { padding: 30px 22px; }
  .hero h1 { font-size: 26px; }
  .stage-specs, .obj-box { grid-template-columns: 1fr; }
}