/* ============================================================
   电气二次设计 · 学习网站 设计系统
   主题：电力蓝 + 电压黄 + 安全绿；卡片化、双编码、进度可视化
   ============================================================ */

:root {
  --c-bg: #f5f7fb;
  --c-surface: #ffffff;
  --c-surface-2: #eef2f9;
  --c-ink: #1b2433;
  --c-ink-soft: #4a5568;
  --c-ink-faint: #8a94a6;
  --c-line: #e2e8f2;

  --c-primary: #1e4fd6;      /* 电力蓝 */
  --c-primary-d: #143a9e;
  --c-primary-l: #e3ecff;
  --c-accent: #f5a623;       /* 电压黄 */
  --c-accent-d: #c97e08;
  --c-success: #1aa672;      /* 安全绿 */
  --c-success-l: #d9f5ea;
  --c-danger: #e23b3b;       /* 警示红 */
  --c-danger-l: #fde2e2;
  --c-info: #0ea5c4;
  --c-info-l: #d8f3fa;

  --radius: 14px;
  --radius-s: 9px;
  --shadow: 0 6px 24px rgba(20,40,90,.08);
  --shadow-hi: 0 12px 40px rgba(20,40,90,.16);
  --maxw: 1180px;
  --font: "Segoe UI", "PingFang SC", "Microsoft YaHei", system-ui, -apple-system, Roboto, Helvetica, Arial, sans-serif;
}

/* 暗色主题 */
[data-theme="dark"] {
  --c-bg: #0f1622;
  --c-surface: #162031;
  --c-surface-2: #1d2a40;
  --c-ink: #e8eefb;
  --c-ink-soft: #aab6cc;
  --c-ink-faint: #6f7d96;
  --c-line: #25324a;
  --c-primary: #4f86ff;
  --c-primary-d: #2f63d6;
  --c-primary-l: #1b2c4d;
  --c-accent: #f7b53c;
  --c-success-l: #103226;
  --c-danger-l: #3a1c1c;
  --c-info-l: #10323a;
  --shadow: 0 6px 24px rgba(0,0,0,.4);
  --shadow-hi: 0 12px 40px rgba(0,0,0,.55);
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  font-family: var(--font);
  background: var(--c-bg);
  color: var(--c-ink);
  line-height: 1.72;
  font-size: 16.5px;
  -webkit-font-smoothing: antialiased;
}

/* ---------- 布局：侧边栏 + 主体 ---------- */
.layout { display: flex; min-height: 100vh; }

.sidebar {
  width: 280px; flex: 0 0 280px;
  background: var(--c-surface);
  border-right: 1px solid var(--c-line);
  position: sticky; top: 0; height: 100vh;
  overflow-y: auto; padding: 22px 16px;
  display: flex; flex-direction: column; gap: 6px;
}
.sidebar .brand {
  display: flex; align-items: center; gap: 10px;
  font-weight: 800; font-size: 17px; color: var(--c-primary-d);
  padding: 4px 8px 14px; letter-spacing: .2px;
}
.sidebar .brand .bolt {
  width: 30px; height: 30px; border-radius: 8px;
  background: linear-gradient(135deg, var(--c-primary), var(--c-accent));
  display: grid; place-items: center; color: #fff; font-size: 17px;
  box-shadow: var(--shadow);
}
.nav-group-title {
  font-size: 11px; text-transform: uppercase; letter-spacing: 1px;
  color: var(--c-ink-faint); margin: 16px 8px 4px; font-weight: 700;
}
.nav-link {
  display: flex; align-items: center; gap: 10px;
  padding: 9px 10px; border-radius: var(--radius-s);
  color: var(--c-ink-soft); text-decoration: none; font-size: 14.5px;
  font-weight: 500; transition: all .15s; position: relative;
}
.nav-link:hover { background: var(--c-surface-2); color: var(--c-ink); }
.nav-link.active { background: var(--c-primary-l); color: var(--c-primary-d); font-weight: 700; }
.nav-link .num {
  flex: 0 0 24px; height: 24px; border-radius: 7px;
  background: var(--c-surface-2); display: grid; place-items: center;
  font-size: 12px; font-weight: 700; color: var(--c-ink-soft);
}
.nav-link.active .num { background: var(--c-primary); color: #fff; }
.nav-link .check { margin-left: auto; font-size: 13px; color: var(--c-success); }
.nav-progress { margin-top: auto; padding: 14px 10px 4px; }
.nav-progress .bar { height: 8px; border-radius: 6px; background: var(--c-surface-2); overflow: hidden; }
.nav-progress .bar > i { display: block; height: 100%; background: linear-gradient(90deg,var(--c-success),#46c98a); width: 0; transition: width .4s; }
.nav-progress small { color: var(--c-ink-faint); font-size: 12px; }

.main { flex: 1 1 auto; min-width: 0; }
.topbar {
  position: sticky; top: 0; z-index: 20;
  background: color-mix(in srgb, var(--c-bg) 86%, transparent);
  backdrop-filter: blur(8px);
  border-bottom: 1px solid var(--c-line);
  display: flex; align-items: center; gap: 12px;
  padding: 12px 28px;
}
.topbar .crumbs { color: var(--c-ink-faint); font-size: 13.5px; font-weight: 600; }
.topbar .crumbs b { color: var(--c-ink); }
.topbar .spacer { flex: 1; }
.icon-btn {
  border: 1px solid var(--c-line); background: var(--c-surface);
  width: 38px; height: 38px; border-radius: 10px; cursor: pointer;
  font-size: 17px; color: var(--c-ink-soft); display: grid; place-items: center;
  transition: all .15s;
}
.icon-btn:hover { border-color: var(--c-primary); color: var(--c-primary); }
.menu-btn { display: none; }

.content { max-width: var(--maxw); margin: 0 auto; padding: 30px 28px 80px; }

/* ---------- Hero / 首页 ---------- */
.hero {
  background: radial-gradient(1200px 500px at 85% -10%, var(--c-primary-l), transparent 60%),
              linear-gradient(135deg, var(--c-primary-d), #2b6bd8 60%, #3f86e0);
  color: #fff; border-radius: 22px; padding: 46px 40px;
  position: relative; overflow: hidden; box-shadow: var(--shadow-hi);
}
.hero h1 { font-size: 34px; margin: 0 0 12px; line-height: 1.2; font-weight: 800; }
.hero p { font-size: 17px; opacity: .94; max-width: 640px; margin: 0 0 22px; }
.hero .pill {
  display: inline-flex; align-items: center; gap: 7px;
  background: rgba(255,255,255,.16); border: 1px solid rgba(255,255,255,.28);
  padding: 6px 13px; border-radius: 30px; font-size: 13.5px; font-weight: 600; margin-right: 8px;
}
.hero .cta {
  display: inline-flex; align-items: center; gap: 8px; margin-top: 8px;
  background: var(--c-accent); color: #2a1c00; font-weight: 800;
  padding: 13px 22px; border-radius: 12px; text-decoration: none; font-size: 15.5px;
  box-shadow: 0 8px 24px rgba(245,166,35,.4); transition: transform .15s;
}
.hero .cta:hover { transform: translateY(-2px); }
.hero .deco { position: absolute; right: -40px; top: -40px; font-size: 280px; opacity: .08; }

/* ---------- 卡片网格 ---------- */
.grid { display: grid; gap: 18px; }
.grid.cols-2 { grid-template-columns: repeat(2,1fr); }
.grid.cols-3 { grid-template-columns: repeat(3,1fr); }
.grid.cols-4 { grid-template-columns: repeat(4,1fr); }
@media (max-width: 900px){ .grid.cols-3,.grid.cols-4{grid-template-columns:repeat(2,1fr);} }
@media (max-width: 620px){ .grid.cols-2,.grid.cols-3,.grid.cols-4{grid-template-columns:1fr;} }

.card {
  background: var(--c-surface); border: 1px solid var(--c-line);
  border-radius: var(--radius); padding: 20px; box-shadow: var(--shadow);
  transition: transform .15s, box-shadow .15s;
}
.card.hov:hover { transform: translateY(-3px); box-shadow: var(--shadow-hi); }
.card .ico { font-size: 26px; margin-bottom: 10px; }
.card h3 { margin: 0 0 8px; font-size: 17px; color: var(--c-ink); }
.card p { margin: 0; color: var(--c-ink-soft); font-size: 14.5px; }
.card .tag { display:inline-block; font-size:11px; font-weight:700; color:var(--c-primary-d);
  background:var(--c-primary-l); padding:2px 9px; border-radius:20px; margin-bottom:10px; }

/* ---------- 章节标题 ---------- */
.page-head { margin-bottom: 26px; }
.page-head .kicker { color: var(--c-primary); font-weight: 800; font-size: 13px; letter-spacing: 1.5px; text-transform: uppercase; }
.page-head h1 { font-size: 32px; margin: 8px 0 10px; line-height: 1.25; }
.page-head .lead { font-size: 17px; color: var(--c-ink-soft); max-width: 760px; }
.level-badge { display:inline-block; font-size:12px; font-weight:700; padding:3px 11px; border-radius:20px; margin-left:8px; vertical-align:middle; }
.lv-1 { background: var(--c-primary-l); color: var(--c-primary-d); }
.lv-2 { background: var(--c-info-l); color: #0a7d95; }
.lv-3 { background: var(--c-accent); color:#2a1c00; }

section.module-sec { margin: 34px 0; scroll-margin-top: 80px; }
.module-sec > h2 {
  font-size: 24px; margin: 0 0 6px; display: flex; align-items: center; gap: 10px;
  border-left: 5px solid var(--c-primary); padding-left: 14px;
}
.module-sec > h2 .sec-no { color: var(--c-primary); font-weight: 800; }
.module-sec h3 { font-size: 19px; margin: 22px 0 8px; color: var(--c-ink); }
.module-sec h4 { font-size: 16px; margin: 16px 0 6px; color: var(--c-primary-d); }
.module-sec p { margin: 10px 0; }
.module-sec ul, .module-sec ol { padding-left: 22px; }
.module-sec li { margin: 6px 0; }

/* ---------- 提示框 callouts ---------- */
.callout {
  border-radius: var(--radius-s); padding: 14px 16px 14px 46px;
  position: relative; margin: 16px 0; font-size: 15px; border: 1px solid;
}
.callout::before { position: absolute; left: 14px; top: 13px; font-size: 18px; }
.callout .ttl { font-weight: 800; display: block; margin-bottom: 3px; }
.callout.tip { background: var(--c-info-l); border-color: #a9e3f2; color: #0c5b6e; }
.callout.tip::before { content: "💡"; }
.callout.warn { background: var(--c-danger-l); border-color: #f5bcbc; color: #9a1c1c; }
.callout.warn::before { content: "⚠️"; }
.callout.key { background: #fff6e6; border-color: #f5d79a; color: #8a5a00; }
.callout.key::before { content: "🔑"; }
.callout.analogy { background: var(--c-primary-l); border-color: #b9cfff; color: #143a9e; }
.callout.analogy::before { content: "🔌"; }
[data-theme="dark"] .callout.key { background:#33260a; color:#f0c46a; }
[data-theme="dark"] .callout.analogy { background:#16243f; color:#bcd0ff; }

/* ---------- 术语 / 知识卡片 ---------- */
.term {
  border: 1px dashed var(--c-line); border-radius: var(--radius-s);
  padding: 12px 14px; margin: 12px 0; background: var(--c-surface-2);
}
.term b { color: var(--c-primary-d); }

/* ---------- 表格 ---------- */
.table-wrap { overflow-x: auto; margin: 16px 0; border-radius: var(--radius-s); border:1px solid var(--c-line); }
table { border-collapse: collapse; width: 100%; font-size: 14.5px; background: var(--c-surface); }
th, td { padding: 10px 13px; text-align: left; border-bottom: 1px solid var(--c-line); }
th { background: var(--c-surface-2); font-weight: 700; color: var(--c-ink); }
tr:last-child td { border-bottom: none; }
td code, th code { background: var(--c-surface-2); padding: 1px 6px; border-radius: 5px; font-size: 13px; }

/* ---------- 图解框 ---------- */
.figure { margin: 22px 0; }
.figure .frame {
  background: var(--c-surface); border: 1px solid var(--c-line);
  border-radius: var(--radius); padding: 16px; box-shadow: var(--shadow);
  text-align: center;
}
.figure .frame svg { max-width: 100%; height: auto; }
.figure .cap { font-size: 13.5px; color: var(--c-ink-faint); text-align: center; margin-top: 10px; }
.figure .cap b { color: var(--c-ink-soft); }

/* 实景照片（区别于手绘 SVG 技术图） */
.figure.photo { margin: 24px 0; }
.figure.photo .frame { position: relative; padding: 0; overflow: hidden; background: var(--c-surface-2); border: 1px solid var(--c-line); }
.figure.photo .frame img { display: block; width: 100%; height: auto; border-radius: calc(var(--radius) - 1px); }
.figure.photo .frame .badge-photo {
  position: absolute; left: 12px; top: 12px; background: rgba(16,24,40,.72); color: #fff;
  font-size: 11px; font-weight: 700; padding: 4px 10px; border-radius: 20px; letter-spacing: .5px;
  -webkit-backdrop-filter: blur(3px); backdrop-filter: blur(3px); pointer-events: none;
}
.figure.photo .cap { display: flex; flex-direction: column; gap: 2px; }
.figure.photo .cap .credit { font-size: 11.5px; color: var(--c-ink-faint); }

/* ---------- 自测题 / 主动回忆 ---------- */
.quiz {
  background: var(--c-surface); border: 1px solid var(--c-line);
  border-radius: var(--radius); padding: 20px; margin: 22px 0; box-shadow: var(--shadow);
  border-top: 4px solid var(--c-accent);
}
.quiz .q-head { display:flex; align-items:center; gap:8px; font-weight:800; color:var(--c-accent-d); margin-bottom:10px; }
.quiz .q { font-weight: 700; font-size: 16px; margin-bottom: 14px; }
.quiz .opts { display: grid; gap: 10px; }
.quiz .opt {
  display: flex; align-items: center; gap: 11px; padding: 12px 14px;
  border: 1.5px solid var(--c-line); border-radius: var(--radius-s);
  cursor: pointer; font-size: 15px; transition: all .12s; background: var(--c-surface);
}
.quiz .opt:hover { border-color: var(--c-primary); }
.quiz .opt .mk {
  flex: 0 0 24px; height: 24px; border-radius: 50%; border: 2px solid var(--c-line);
  display: grid; place-items: center; font-weight: 800; font-size: 13px; color: var(--c-ink-faint);
}
.quiz .opt.correct { border-color: var(--c-success); background: var(--c-success-l); }
.quiz .opt.correct .mk { background: var(--c-success); border-color: var(--c-success); color: #fff; }
.quiz .opt.wrong { border-color: var(--c-danger); background: var(--c-danger-l); }
.quiz .opt.wrong .mk { background: var(--c-danger); border-color: var(--c-danger); color: #fff; }
.quiz .opt.lock { pointer-events: none; }
.quiz .explain { margin-top: 14px; padding: 13px 15px; border-radius: var(--radius-s);
  background: var(--c-surface-2); font-size: 14.5px; display: none; }
.quiz .explain.show { display: block; }
.quiz .explain b { color: var(--c-primary-d); }

/* ---------- 例题 / 分步 ---------- */
.example { border: 1px solid var(--c-line); border-radius: var(--radius); margin: 22px 0; overflow: hidden; box-shadow: var(--shadow); }
.example .ex-head { background: var(--c-primary-d); color: #fff; padding: 13px 18px; font-weight: 800; display:flex; align-items:center; gap:9px; }
.example .ex-body { padding: 18px; }
.example .step { display: flex; gap: 14px; padding: 13px 0; border-bottom: 1px dashed var(--c-line); }
.example .step:last-child { border-bottom: none; }
.example .step .n { flex: 0 0 32px; height: 32px; border-radius: 50%; background: var(--c-primary-l); color: var(--c-primary-d); display:grid; place-items:center; font-weight:800; }
.example .step .body { flex: 1; }
.example .step .body b { color: var(--c-primary-d); }
.example .reveal { margin-top: 14px; }
.btn {
  border: none; cursor: pointer; font-weight: 700; font-family: var(--font);
  padding: 11px 18px; border-radius: 10px; font-size: 14.5px; transition: all .15s;
}
.btn.primary { background: var(--c-primary); color: #fff; }
.btn.primary:hover { background: var(--c-primary-d); }
.btn.ghost { background: var(--c-surface-2); color: var(--c-ink); }
.btn.ghost:hover { background: var(--c-line); }

/* ---------- 进度 / 完成态 ---------- */
.complete-box {
  display:flex; align-items:center; gap:14px; margin: 28px 0 8px;
  background: var(--c-success-l); border:1px solid #9fe3c5; border-radius: var(--radius);
  padding: 16px 18px;
}
.complete-box .ring { flex:0 0 46px; height:46px; border-radius:50%; border:3px solid var(--c-success);
  display:grid; place-items:center; color:var(--c-success); font-size:22px; }
.complete-box .txt b { color: var(--c-success); }
.complete-box .txt { flex:1; font-size:14.5px; color: var(--c-ink-soft); }
.complete-box .txt .next-review { color: var(--c-ink-faint); font-size:13px; }

/* ---------- 学习法提示条 ---------- */
.scimethod {
  display:flex; gap:10px; align-items:flex-start; font-size:13.5px; color:var(--c-ink-faint);
  background:var(--c-surface-2); border-radius: var(--radius-s); padding:10px 14px; margin:10px 0;
  border:1px solid var(--c-line);
}
.scimethod .badge { flex:0 0 auto; font-weight:800; color:var(--c-primary-d); background:var(--c-primary-l);
  padding:2px 9px; border-radius:20px; font-size:12px; }

/* ---------- 上/下页导航 ---------- */
.pager { display:flex; justify-content:space-between; gap:14px; margin-top:40px; }
.pager a { flex:1; text-decoration:none; border:1px solid var(--c-line); border-radius: var(--radius);
  padding:14px 18px; color:var(--c-ink-soft); background:var(--c-surface); transition:all .15s; box-shadow:var(--shadow); }
.pager a:hover { border-color:var(--c-primary); color:var(--c-primary); }
.pager a .lbl { font-size:12px; color:var(--c-ink-faint); }
.pager a .ttl { font-weight:700; color:var(--c-ink); font-size:15px; }
.pager a.next { text-align:right; }

/* ---------- 首页仪表盘 ---------- */
.dash { display:grid; grid-template-columns: 1fr 1fr; gap:18px; margin: 26px 0; }
@media (max-width:760px){ .dash{grid-template-columns:1fr;} }
.dash .panel { background: var(--c-surface); border:1px solid var(--c-line); border-radius: var(--radius); padding:20px; box-shadow:var(--shadow); }
.dash .panel h3 { margin:0 0 6px; font-size:16px; }
.dash .big-num { font-size:40px; font-weight:800; color:var(--c-primary); line-height:1; }
.dash .big-num small { font-size:15px; color:var(--c-ink-faint); font-weight:600; }
.roadmap { counter-reset: rm; }
.roadmap .rm-item { display:flex; gap:14px; padding:14px 0; border-bottom:1px dashed var(--c-line); }
.roadmap .rm-item:last-child{border-bottom:none;}
.roadmap .rm-item .rn { counter-increment: rm; flex:0 0 34px; height:34px; border-radius:10px;
  background:var(--c-primary-l); color:var(--c-primary-d); display:grid; place-items:center; font-weight:800; }
.roadmap .rm-item .rn::before { content: counter(rm); }
.roadmap .rm-item .ri b { display:block; font-size:15.5px; color:var(--c-ink); }
.roadmap .rm-item .ri span { font-size:13.5px; color:var(--c-ink-soft); }

/* 页脚 */
.foot { text-align:center; color:var(--c-ink-faint); font-size:13px; padding:30px 20px; border-top:1px solid var(--c-line); margin-top:30px; }

/* 移动端抽屉 */
@media (max-width: 880px){
  .sidebar { position: fixed; left: 0; top: 0; z-index: 60; transform: translateX(-100%); transition: transform .25s; box-shadow: var(--shadow-hi); }
  .sidebar.open { transform: translateX(0); }
  .menu-btn { display:grid; }
  .content { padding: 22px 16px 70px; }
  .topbar { padding: 12px 16px; }
  .hero { padding: 34px 24px; }
  .hero h1 { font-size: 27px; }
  .overlay { position: fixed; inset:0; background: rgba(0,0,0,.4); z-index:55; display:none; }
  .overlay.show { display:block; }
}
@media (min-width: 881px){ .overlay { display:none !important; } }

/* 代码/公式 */
code.inline { background: var(--c-surface-2); padding: 2px 7px; border-radius: 6px; font-size: 13.5px; font-family: "Cascadia Code", Consolas, monospace; }
.formula { background: var(--c-surface-2); border:1px solid var(--c-line); border-radius:10px; padding:12px 16px; margin:12px 0; font-family:"Cascadia Code",Consolas,monospace; font-size:15px; overflow-x:auto; }