/* ==========================================================================
   Harness Engineering 图解教程 — 设计系统
   基调：学术图解风 · 暖纸色 + 靛蓝紫 + 墨黑 · 宋体标题
   ========================================================================== */

:root {
  /* 色板 */
  --paper: #faf6ef;
  --paper-2: #f3ecdf;
  --paper-3: #ece3d2;
  --ink: #26201a;
  --ink-soft: #5f554a;
  --ink-faint: #8a7f72;
  --line: #e2d8c6;
  --line-strong: #cdbfa6;

  --amber: #4f46a5;
  --amber-deep: #3730a3;
  --amber-soft: #e6e3f7;
  --amber-pale: #f1effb;

  --teal: #2c6658;
  --teal-soft: #dcebe4;
  --red: #b0483f;
  --red-soft: #f6dfdb;
  --blue: #46638f;
  --blue-soft: #dde6f2;
  --violet: #6b5b95;
  --violet-soft: #e7e2f1;

  /* 字体 */
  --font-serif: "Noto Serif SC", "Source Han Serif SC", "Songti SC", STSong, SimSun, serif;
  --font-sans: "PingFang SC", "Microsoft YaHei", "Noto Sans SC", "Helvetica Neue", "Segoe UI", sans-serif;
  --font-mono: "JetBrains Mono", "Cascadia Code", Consolas, "Courier New", monospace;

  /* 布局 */
  --sidebar-w: 292px;
  --content-max: 900px;
  --radius: 14px;
  --shadow-1: 0 1px 2px rgba(38, 32, 26, .06), 0 8px 24px -12px rgba(38, 32, 26, .18);
  --shadow-2: 0 2px 6px rgba(38, 32, 26, .08), 0 18px 44px -16px rgba(38, 32, 26, .28);
}

* { box-sizing: border-box; }

html { scroll-behavior: smooth; scroll-padding-top: 24px; }

body {
  margin: 0;
  background: var(--paper);
  color: var(--ink);
  font-family: var(--font-sans);
  font-size: 16px;
  line-height: 1.75;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

/* 纸张颗粒纹理背景 */
body::before {
  content: "";
  position: fixed;
  inset: 0;
  pointer-events: none;
  z-index: 0;
  opacity: .5;
  background-image: radial-gradient(rgba(38,32,26,.045) 1px, transparent 1px);
  background-size: 22px 22px;
}

::selection { background: var(--amber); color: #fff; }

a { color: var(--amber-deep); text-decoration: none; }
a:hover { text-decoration: underline; text-underline-offset: 3px; }

h1, h2, h3, h4 { font-family: var(--font-serif); line-height: 1.35; }

/* ============ 侧边栏 ============ */
.sidebar {
  position: fixed;
  top: 0; left: 0; bottom: 0;
  width: var(--sidebar-w);
  background:
    radial-gradient(120% 60% at 0% 0%, rgba(79,70,165,.16), transparent 55%),
    linear-gradient(180deg, #241f18, #1b1712);
  color: var(--sidebar-ink);
  overflow-y: auto;
  z-index: 40;
  border-right: 1px solid rgba(0,0,0,.4);
}

.sidebar::-webkit-scrollbar { width: 8px; }
.sidebar::-webkit-scrollbar-thumb { background: rgba(239,230,216,.22); border-radius: 4px; }

.side-brand {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 26px 24px 20px;
  border-bottom: 1px solid rgba(239,230,216,.12);
}

.side-brand svg { flex: none; }

.side-brand .brand-name {
  font-family: var(--font-serif);
  font-size: 19px;
  letter-spacing: .06em;
  color: #f5ecd9;
  line-height: 1.3;
}
.side-brand .brand-sub {
  font-size: 11px;
  letter-spacing: .22em;
  color: rgba(239,230,216,.55);
  margin-top: 2px;
}

.side-nav { padding: 14px 12px 40px; }

.side-nav .nav-part {
  font-size: 11px;
  letter-spacing: .28em;
  color: rgba(239,230,216,.42);
  margin: 22px 12px 8px;
  text-transform: uppercase;
  display: flex;
  align-items: center;
  gap: 8px;
}
.side-nav .nav-part::after {
  content: "";
  flex: 1;
  height: 1px;
  background: rgba(239,230,216,.14);
}

.side-nav a.nav-item {
  display: flex;
  align-items: baseline;
  gap: 10px;
  padding: 7px 12px;
  border-radius: 9px;
  color: rgba(239,230,216,.78);
  font-size: 14.5px;
  line-height: 1.4;
  border-left: 2px solid transparent;
  transition: background .18s, color .18s, border-color .18s;
}
.side-nav a.nav-item:hover { background: rgba(239,230,216,.07); color: #fff; text-decoration: none; }
.side-nav a.nav-item .no {
  font-family: var(--font-mono);
  font-size: 11px;
  color: rgba(239,230,216,.45);
  min-width: 22px;
}
.side-nav a.nav-item.active {
  background: linear-gradient(90deg, rgba(79,70,165,.28), rgba(79,70,165,.08));
  border-left-color: var(--amber);
  color: #e8e6fb;
}
.side-nav a.nav-item.active .no { color: var(--amber); }

.side-foot {
  padding: 16px 24px 28px;
  border-top: 1px solid rgba(239,230,216,.12);
  font-size: 11.5px;
  color: rgba(239,230,216,.45);
  line-height: 1.7;
}

/* ============ 主内容 ============ */
.main {
  margin-left: var(--sidebar-w);
  position: relative;
  z-index: 1;
}

.content { max-width: var(--content-max); margin: 0 auto; padding: 0 44px 120px; }

/* 顶部工具条 */
.topbar {
  position: sticky;
  top: 0;
  z-index: 30;
  display: flex;
  align-items: center;
  gap: 14px;
  max-width: var(--content-max);
  margin: 0 auto;
  padding: 14px 44px;
  background: linear-gradient(180deg, rgba(250,246,239,.96), rgba(250,246,239,.82));
  backdrop-filter: blur(8px);
  border-bottom: 1px solid rgba(226,216,198,.8);
}
.topbar .crumb { font-size: 13px; color: var(--ink-faint); letter-spacing: .04em; }
.topbar .crumb b { color: var(--amber-deep); font-weight: 600; }
.topbar .progress-wrap { flex: 1; height: 4px; background: var(--paper-3); border-radius: 2px; overflow: hidden; }
.topbar .progress-bar { height: 100%; width: 0; background: linear-gradient(90deg, var(--amber), var(--amber-deep)); border-radius: 2px; transition: width .12s linear; }

/* ============ Hero ============ */
.hero {
  padding: 64px 0 40px;
}
.hero .kicker {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  font-size: 13px;
  letter-spacing: .3em;
  color: var(--amber-deep);
  font-weight: 600;
  border: 1px solid var(--line-strong);
  background: var(--amber-pale);
  padding: 6px 14px;
  border-radius: 999px;
}
.hero h1 {
  font-size: clamp(34px, 5vw, 52px);
  letter-spacing: .02em;
  margin: 22px 0 10px;
}
.hero h1 .hl {
  color: var(--amber-deep);
  position: relative;
  white-space: nowrap;
}
.hero h1 .hl::after {
  content: "";
  position: absolute;
  left: 0; right: 0; bottom: 4px;
  height: 10px;
  background: linear-gradient(90deg, rgba(79,70,165,.32), rgba(79,70,165,.08));
  z-index: -1;
  border-radius: 2px;
}
.hero .sub {
  font-size: 17px;
  color: var(--ink-soft);
  max-width: 620px;
  margin: 6px 0 26px;
  font-family: var(--font-serif);
}
.hero .meta-chips { display: flex; flex-wrap: wrap; gap: 10px; margin-bottom: 34px; }
.hero .meta-chips span {
  font-size: 13px;
  background: var(--paper-2);
  border: 1px solid var(--line);
  color: var(--ink-soft);
  padding: 6px 14px;
  border-radius: 999px;
}
.hero .meta-chips span b { color: var(--ink); font-weight: 600; }

.hero-actions { display: flex; flex-wrap: wrap; gap: 12px; margin-bottom: 40px; }
.btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  font-size: 14.5px;
  font-weight: 600;
  padding: 11px 22px;
  border-radius: 999px;
  border: 1px solid transparent;
  cursor: pointer;
  transition: transform .15s, box-shadow .15s, background .15s;
}
.btn:hover { text-decoration: none; transform: translateY(-1px); }
.btn-primary { background: linear-gradient(135deg, var(--amber), var(--amber-deep)); color: #fff; box-shadow: 0 6px 18px -6px rgba(79,70,165,.55); }
.btn-primary:hover { box-shadow: 0 10px 26px -6px rgba(79,70,165,.6); }
.btn-ghost { background: transparent; border-color: var(--line-strong); color: var(--ink); }
.btn-ghost:hover { background: var(--paper-2); }

/* 目录卡片（五部分速览） */
.parts-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
  gap: 14px;
  margin: 8px 0 10px;
}
.part-card {
  background: var(--paper-2);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 18px;
  transition: transform .18s, box-shadow .18s, border-color .18s;
}
.part-card:hover { transform: translateY(-3px); box-shadow: var(--shadow-1); border-color: var(--line-strong); text-decoration: none; }
.part-card .pc-no { font-family: var(--font-mono); font-size: 12px; color: var(--amber-deep); letter-spacing: .1em; }
.part-card .pc-name { font-family: var(--font-serif); font-size: 17px; margin: 6px 0 2px; }
.part-card .pc-desc { font-size: 12.5px; color: var(--ink-faint); line-height: 1.5; }

/* ============ 章节通用 ============ */
.part-banner {
  display: flex;
  align-items: center;
  gap: 18px;
  margin: 72px 0 8px;
  padding-bottom: 16px;
  border-bottom: 2px solid var(--ink);
}
.part-banner .pb-no {
  font-family: var(--font-serif);
  font-size: 40px;
  color: var(--amber);
  line-height: 1;
}
.part-banner .pb-txt h2 { margin: 0; font-size: 26px; letter-spacing: .04em; }
.part-banner .pb-txt p { margin: 2px 0 0; color: var(--ink-faint); font-size: 14px; }

section.chapter { margin: 56px 0; scroll-margin-top: 30px; }
.chapter-head { margin-bottom: 26px; }
.chapter-head .ch-no {
  font-family: var(--font-mono);
  font-size: 13px;
  letter-spacing: .18em;
  color: var(--amber-deep);
  display: flex;
  align-items: center;
  gap: 10px;
}
.chapter-head .ch-no::before { content: ""; width: 30px; height: 2px; background: var(--amber); }
.chapter-head h3 { font-size: 29px; margin: 8px 0 6px; letter-spacing: .02em; }
.chapter-head .ch-sub { color: var(--ink-faint); font-size: 15px; font-family: var(--font-serif); }

/* 一句话定义 */
.oneline {
  background: linear-gradient(135deg, var(--amber-pale), var(--paper-2));
  border: 1px solid var(--line-strong);
  border-left: 5px solid var(--amber);
  border-radius: var(--radius);
  padding: 18px 22px;
  font-size: 17.5px;
  font-family: var(--font-serif);
  margin: 20px 0 8px;
}
.oneline b { color: var(--amber-deep); }

/* 引用块 */
.quote {
  background: var(--paper-2);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 18px 22px;
  margin: 18px 0;
  position: relative;
}
.quote::before {
  content: "❝";
  position: absolute;
  top: 4px; left: 14px;
  font-size: 30px;
  color: var(--amber);
  opacity: .5;
}
.quote p { margin: 4px 0; font-family: var(--font-serif); font-size: 15.5px; }
.quote .src { display: block; margin-top: 8px; font-size: 12.5px; color: var(--ink-faint); font-family: var(--font-sans); }
.quote .src b { color: var(--amber-deep); }

/* 要点列表 */
ul.points, ol.points { padding-left: 2px; list-style: none; margin: 16px 0; }
ul.points li, ol.points li {
  position: relative;
  padding: 7px 0 7px 30px;
  border-bottom: 1px dashed var(--line);
}
ul.points li:last-child, ol.points li:last-child { border-bottom: none; }
ul.points li::before {
  content: "";
  position: absolute;
  left: 4px; top: 16px;
  width: 10px; height: 10px;
  border: 2.5px solid var(--amber);
  border-radius: 3px;
  transform: rotate(45deg);
}
ol.points { counter-reset: pt; }
ol.points li::before {
  counter-increment: pt;
  content: counter(pt);
  font-family: var(--font-mono);
  font-size: 12px;
  font-weight: 700;
  color: var(--amber-deep);
  background: var(--amber-soft);
  width: 22px; height: 22px;
  border: none;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  top: 9px; left: 0;
  transform: none;
}
ul.points li b, ol.points li b { color: var(--amber-deep); font-weight: 650; }
ul.points li code, ol.points li code, p code, td code, .gloss code {
  font-family: var(--font-mono);
  font-size: .86em;
  background: var(--paper-3);
  border: 1px solid var(--line);
  border-radius: 5px;
  padding: 1px 7px;
  color: var(--amber-deep);
}

/* 小标签 */
.tag {
  display: inline-block;
  font-size: 12px;
  font-weight: 600;
  padding: 2px 10px;
  border-radius: 999px;
  margin-right: 6px;
  vertical-align: 1px;
}
.tag-amber { background: var(--amber-soft); color: var(--amber-deep); }
.tag-teal { background: var(--teal-soft); color: var(--teal); }
.tag-red { background: var(--red-soft); color: var(--red); }
.tag-blue { background: var(--blue-soft); color: var(--blue); }
.tag-violet { background: var(--violet-soft); color: var(--violet); }
.tag-ink { background: var(--ink); color: var(--paper); }

/* 图解容器 */
.diagram {
  margin: 26px 0;
  background: var(--paper-2);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 18px 18px 12px;
  box-shadow: var(--shadow-1);
}
.diagram svg { display: block; width: 100%; height: auto; }
.diagram figcaption {
  font-size: 13px;
  color: var(--ink-faint);
  text-align: center;
  padding-top: 10px;
  border-top: 1px dashed var(--line);
  margin-top: 12px;
}
.diagram figcaption b { color: var(--amber-deep); }

/* 提示框 */
.callout {
  border-radius: var(--radius);
  padding: 16px 20px;
  margin: 18px 0;
  border: 1px solid;
  display: flex;
  gap: 12px;
}
.callout .ico { font-size: 20px; line-height: 1.4; flex: none; }
.callout p { margin: 0; font-size: 14.5px; }
.callout .co-title { font-weight: 700; display: block; margin-bottom: 2px; font-family: var(--font-serif); font-size: 15.5px; }
.callout-tip { background: var(--teal-soft); border-color: #b9d6c9; }
.callout-tip .co-title { color: var(--teal); }
.callout-warn { background: var(--red-soft); border-color: #e8c3bd; }
.callout-warn .co-title { color: var(--red); }
.callout-key { background: var(--amber-pale); border-color: #c9c4ec; }
.callout-key .co-title { color: var(--amber-deep); }

/* 数据卡 */
.stats {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(120px, 1fr));
  gap: 12px;
  margin: 20px 0;
}
.stat {
  background: var(--paper-2);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 16px 14px;
  text-align: center;
}
.stat .num { font-family: var(--font-serif); font-size: 26px; font-weight: 700; color: var(--amber-deep); line-height: 1.2; }
.stat .lbl { font-size: 12.5px; color: var(--ink-faint); margin-top: 4px; }

/* 表格 */
.tbl-wrap { overflow-x: auto; margin: 20px 0; border-radius: var(--radius); border: 1px solid var(--line); box-shadow: var(--shadow-1); }
table.tbl { width: 100%; border-collapse: collapse; font-size: 14px; background: var(--paper); }
table.tbl th {
  background: var(--ink);
  color: var(--paper);
  font-family: var(--font-serif);
  font-weight: 600;
  text-align: left;
  padding: 10px 14px;
  white-space: nowrap;
}
table.tbl td { padding: 9px 14px; border-top: 1px solid var(--line); vertical-align: top; }
table.tbl tbody tr:nth-child(even) { background: var(--paper-2); }
table.tbl td:first-child { font-weight: 600; color: var(--ink); white-space: nowrap; }
table.tbl .good { color: var(--teal); font-weight: 600; }
table.tbl .bad { color: var(--red); font-weight: 600; }
table.tbl .hl-cell { background: var(--amber-pale); }

/* 代码块 */
.codeblock {
  background: #221d16;
  color: #efe6d4;
  border-radius: var(--radius);
  padding: 18px 20px;
  font-family: var(--font-mono);
  font-size: 13px;
  line-height: 1.7;
  overflow-x: auto;
  margin: 18px 0;
  position: relative;
  border: 1px solid #332c22;
}
.codeblock .cb-title {
  position: absolute;
  top: 8px; right: 12px;
  font-size: 11px;
  color: rgba(239,230,216,.5);
  font-family: var(--font-sans);
  letter-spacing: .08em;
}
.codeblock .cm { color: #8f8574; }
.codeblock .cn { color: #a5a0e0; }
.codeblock .cs { color: #9ec3a0; }
.codeblock .ck { color: #7fb3c9; }

/* 案例卡片 */
.case-card {
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--paper);
  overflow: hidden;
  margin: 26px 0;
  box-shadow: var(--shadow-1);
}
.case-head {
  display: flex;
  align-items: center;
  gap: 14px;
  padding: 16px 22px;
  background: linear-gradient(135deg, var(--ink), #38302a);
  color: var(--paper);
}
.case-head .ch-avatar {
  width: 44px; height: 44px;
  border-radius: 12px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-family: var(--font-serif);
  font-size: 20px;
  flex: none;
}
.case-head h4 { margin: 0; font-size: 19px; color: #f5ecd9; }
.case-head .ch-meta { font-size: 12.5px; color: rgba(239,230,216,.6); margin-top: 2px; }
.case-body { padding: 20px 24px 24px; }

/* 双栏对比 */
.compare { display: grid; grid-template-columns: 1fr 1fr; gap: 14px; margin: 18px 0; }
.compare .side {
  border-radius: var(--radius);
  padding: 16px 18px;
  border: 1px solid var(--line);
}
.compare .side.good { background: var(--teal-soft); border-color: #b9d6c9; }
.compare .side.bad { background: var(--red-soft); border-color: #e8c3bd; }
.compare .side h5 { margin: 0 0 8px; font-size: 15px; font-family: var(--font-serif); }
.compare .side.good h5 { color: var(--teal); }
.compare .side.bad h5 { color: var(--red); }
.compare .side ul { margin: 0; padding-left: 18px; font-size: 13.5px; }
.compare .side ul li { margin: 4px 0; }

/* 词条卡片（速查） */
.gloss-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(250px, 1fr));
  gap: 14px;
  margin: 20px 0;
}
.gloss {
  background: var(--paper-2);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 16px 18px;
  transition: transform .18s, box-shadow .18s;
}
.gloss:hover { transform: translateY(-2px); box-shadow: var(--shadow-1); }
.gloss h5 { margin: 0 0 6px; font-size: 15.5px; }
.gloss h5 .en { color: var(--ink-faint); font-family: var(--font-mono); font-size: 12px; font-weight: 400; margin-left: 6px; }
.gloss p { margin: 0; font-size: 13.5px; color: var(--ink-soft); line-height: 1.65; }

/* 视频卡片 */
.video-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(240px, 1fr));
  gap: 16px;
  margin: 20px 0;
}
.video-card {
  border: 1px solid var(--line);
  border-radius: var(--radius);
  overflow: hidden;
  background: var(--paper);
  transition: transform .18s, box-shadow .18s;
  display: block;
  color: inherit;
}
.video-card:hover { transform: translateY(-3px); box-shadow: var(--shadow-2); text-decoration: none; }
.video-card .vc-thumb { position: relative; aspect-ratio: 16/9; background: var(--ink); }
.video-card .vc-thumb svg { width: 100%; height: 100%; display: block; }
.video-card .vc-play {
  position: absolute;
  inset: 0;
  display: flex;
  align-items: center;
  justify-content: center;
}
.video-card .vc-play .pbtn {
  width: 52px; height: 52px;
  border-radius: 50%;
  background: rgba(79,70,165,.92);
  display: flex;
  align-items: center;
  justify-content: center;
  color: #fff;
  box-shadow: 0 6px 18px rgba(0,0,0,.4);
  transition: transform .18s;
}
.video-card:hover .vc-play .pbtn { transform: scale(1.08); }
.video-card .vc-body { padding: 12px 14px 14px; }
.video-card .vc-title { font-size: 14px; font-weight: 600; margin: 0 0 4px; line-height: 1.5; }
.video-card .vc-meta { font-size: 12px; color: var(--ink-faint); display: flex; gap: 8px; align-items: center; }
.video-card .vc-meta .dur { background: var(--amber-soft); color: var(--amber-deep); padding: 0 8px; border-radius: 4px; font-family: var(--font-mono); font-size: 11px; }

/* ============ 页脚 ============ */
.foot {
  border-top: 1px solid var(--line);
  margin-top: 90px;
  padding-top: 26px;
  color: var(--ink-faint);
  font-size: 13.5px;
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
  justify-content: space-between;
  align-items: center;
}
.foot .links a { margin-left: 12px; }

/* 回到顶部 */
#toTop {
  position: fixed;
  right: 26px; bottom: 26px;
  width: 46px; height: 46px;
  border-radius: 50%;
  background: var(--ink);
  color: var(--amber);
  border: 1px solid #3d352b;
  font-size: 18px;
  cursor: pointer;
  opacity: 0;
  transform: translateY(10px);
  pointer-events: none;
  transition: opacity .25s, transform .25s;
  z-index: 50;
}
#toTop.show { opacity: 1; transform: none; pointer-events: auto; }
#toTop:hover { background: var(--amber-deep); color: #fff; }

/* 移动端汉堡 */
#menuBtn {
  display: none;
  position: fixed;
  top: 14px; left: 14px;
  z-index: 60;
  width: 42px; height: 42px;
  border-radius: 10px;
  background: var(--ink);
  color: var(--amber);
  border: 1px solid #3d352b;
  font-size: 18px;
  cursor: pointer;
}
.side-mask {
  display: none;
  position: fixed;
  inset: 0;
  background: rgba(27,23,18,.55);
  z-index: 39;
  backdrop-filter: blur(2px);
}

/* 进场动画 */
.reveal { opacity: 0; transform: translateY(22px); transition: opacity .6s ease, transform .6s ease; }
.reveal.in { opacity: 1; transform: none; }

/* ============ 响应式 ============ */
@media (max-width: 1020px) {
  :root { --sidebar-w: 256px; }
  .content { padding: 0 30px 100px; }
  .topbar { padding: 14px 30px; }
}
@media (max-width: 860px) {
  .sidebar { transform: translateX(-100%); transition: transform .28s ease; }
  .sidebar.open { transform: none; box-shadow: 24px 0 60px rgba(0,0,0,.4); }
  .side-mask.show { display: block; }
  #menuBtn { display: flex; align-items: center; justify-content: center; }
  .main { margin-left: 0; }
  .topbar { padding-left: 70px; }
  .hero { padding-top: 46px; }
  .compare { grid-template-columns: 1fr; }
}