/* ==========================================================================
   Verse Wiki — style.css
   Vivid+Co 设计系统:黑曜石深空 + 骨白排版 + 棱镜色散(源自 DESIGN.md)
   唯一样式文件 —— 全部组件的类名保持不变,页面只写标记不写样式。
   ========================================================================== */

/* --------------------------------------------------------------------------
   0. 自托管字体(零运行时外链)
   General Sans:拉丁显示/正文/UI(Neue Montreal 的近亲)
   Noto Sans SC:中文,子集化可变字重(轻盈的电影感中文)
   JetBrains Mono:代码,子集化可变字重
   -------------------------------------------------------------------------- */
@font-face {
  font-family: 'General Sans';
  src: url('../fonts/general-sans-400.woff2') format('woff2');
  font-weight: 400; font-style: normal; font-display: swap;
}
@font-face {
  font-family: 'General Sans';
  src: url('../fonts/general-sans-500.woff2') format('woff2');
  font-weight: 500; font-style: normal; font-display: swap;
}
@font-face {
  font-family: 'General Sans';
  src: url('../fonts/general-sans-700.woff2') format('woff2');
  font-weight: 700; font-style: normal; font-display: swap;
}
@font-face {
  font-family: 'Noto Sans SC VF';
  src: url('../fonts/noto-sans-sc-subset.woff2') format('woff2');
  font-weight: 100 900; font-style: normal; font-display: swap;
}
@font-face {
  font-family: 'JetBrains Mono VF';
  src: url('../fonts/jetbrains-mono-subset.woff2') format('woff2');
  font-weight: 100 800; font-style: normal; font-display: swap;
}

/* --------------------------------------------------------------------------
   1. 设计令牌
   -------------------------------------------------------------------------- */
:root {
  /* 颜色 —— Transmission 单色纪律:纯黑画布 + 印刷白 + 灰阶,无彩色 */
  --color-bone: #f2f2ef;
  --color-obsidian: #000000;
  --color-graphite: #4a4a48;
  --color-ash: #2b2b29;
  --color-fog: #8f8f8b;
  --color-black: #000000;
  /* 原棱镜三通道 → 灰阶三级(保留变量名,所有引用自动单色化) */
  --prism-red: #f2f2ef;
  --prism-cyan: #b9b9b5;
  --prism-lime: #6f6f6b;

  /* 语义色(交互反馈保留极低饱和的功能色,可用性优先) */
  --color-ok-text: #a9d6b4;
  --color-ok-bg: rgba(169, 214, 180, 0.08);
  --color-ok-border: rgba(169, 214, 180, 0.45);
  --color-no-text: #d6a9a9;
  --color-no-bg: rgba(214, 169, 169, 0.08);
  --color-no-border: rgba(214, 169, 169, 0.45);

  /* 表面层级(近黑灰阶) */
  --surface-1: #0a0a0a;   /* 卡片抬升面 */
  --surface-2: #0d0d0d;   /* 代码块面 */
  --surface-veil: #161616; /* 强调卡暗面 */

  /* 字体栈 */
  --font-sans: 'General Sans', 'Noto Sans SC VF', ui-sans-serif, system-ui, -apple-system,
    "Segoe UI", "PingFang SC", "Microsoft YaHei", "Source Han Sans SC", sans-serif;
  --font-mono: 'JetBrains Mono VF', ui-monospace, "Cascadia Code", Consolas,
    'Noto Sans SC VF', "Microsoft YaHei", monospace;

  /* 字号(源自 DESIGN.md 的电影感尺度) */
  --text-caption: 15px;
  --text-body-sm: 18px;
  --text-body: 20px;
  --text-body-lg: 22px;
  --text-heading-sm: 33px;
  --text-heading: 36px;
  --text-heading-lg: 56px;
  --text-display-sm: 88px;
  --text-display: 120px;

  /* 字重 */
  --fw-regular: 400;
  --fw-medium: 500;
  --fw-bold: 700;
  /* 大字号中文的光学补偿:400 的中文视觉偏重,故大标题走更轻的可变字重 */
  --fw-display-cjk: 350;

  /* 间距(base 4px) */
  --spacing-8: 8px;
  --spacing-16: 16px;
  --spacing-20: 20px;
  --spacing-24: 24px;
  --spacing-40: 40px;
  --spacing-56: 56px;
  --spacing-64: 64px;
  --spacing-72: 72px;
  --spacing-108: 108px;

  /* 布局 */
  --page-max-width: 1280px;
  --page-pad-x: 40px;
  --section-gap: 108px;
  --card-padding: 24px;

  /* 圆角(Transmission:全部直角,印刷品的锋利边缘) */
  --radius-card: 0px;
  --radius-button: 0px;
  --radius-tag: 0px;
  --radius-nav: 0px;
  --radius-code: 0px;

  /* 运动:招牌缓动曲线(慢起 + 果断收束,如光学对焦) */
  --ease: cubic-bezier(0.52, 0.01, 0, 1);
  --dur: 0.5s;
  --dur-fast: 0.28s;

  /* 代码块 */
  --code-bg: #0a0a0a;
  --code-border: #262624;
  --code-fg: #ededea;
}

@media (max-width: 900px) {
  :root {
    --text-display: 62px;
    --text-display-sm: 52px;
    --text-heading-lg: 40px;
    --text-heading: 30px;
    --text-heading-sm: 26px;
    --page-pad-x: 22px;
    --section-gap: 72px;
  }
}

/* --------------------------------------------------------------------------
   2. 基础与排版
   -------------------------------------------------------------------------- */
*, *::before, *::after { box-sizing: border-box; }

html { scroll-behavior: smooth; -webkit-text-size-adjust: 100%; }

body {
  margin: 0;
  background: var(--color-obsidian);
  color: var(--color-bone);
  font-family: var(--font-sans);
  font-size: var(--text-body);
  line-height: 1.6;
  letter-spacing: -0.01em;
  overflow-x: hidden;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

/* 画布:平坦纯黑(Transmission 印刷底,无渐变无光晕) */
body::before {
  content: "";
  position: fixed;
  inset: 0;
  z-index: -2;
  pointer-events: none;
  background: var(--color-obsidian);
}

h1, h2, h3, h4, h5, h6 {
  font-family: var(--font-sans);
  font-weight: var(--fw-regular);
  letter-spacing: -0.02em;
  line-height: 1.08;
  color: var(--color-bone);
  margin: 0 0 var(--spacing-24);
  text-wrap: balance;
}

h1 { font-size: var(--text-heading-lg); letter-spacing: -0.03em; }
h2 { font-size: var(--text-heading-sm); }
h3 { font-size: var(--text-body-lg); line-height: 1.2; }
h4 { font-size: var(--text-body); }

p { margin: 0 0 var(--spacing-20); }

ul, ol { margin: 0 0 var(--spacing-20); padding-left: 1.4em; }
li { margin-bottom: var(--spacing-8); }

a { color: var(--color-bone); text-decoration: none; }

strong, b { font-weight: var(--fw-medium); }

figure { margin: 0; }

hr {
  border: none;
  border-top: 1px solid var(--color-ash);
  margin: var(--spacing-40) 0;
}

table {
  border-collapse: collapse;
  width: 100%;
  font-size: var(--text-body-sm);
  margin: 0 0 var(--spacing-24);
}

th, td {
  text-align: left;
  padding: 12px 16px;
  border-bottom: 1px solid var(--color-ash);
  font-weight: var(--fw-regular);
}

th {
  text-transform: uppercase;
  font-size: var(--text-caption);
  letter-spacing: 0.04em;
  color: var(--color-fog);
}

.table-scroll {
  overflow-x: auto;
  -webkit-overflow-scrolling: touch;
  margin: 0 0 var(--spacing-24);
}
.table-scroll table { margin-bottom: 0; }

:not(.table-scroll) > table th,
:not(.table-scroll) > table td {
  overflow-wrap: anywhere;
  word-break: break-word;
}

code { font-family: var(--font-mono); }

p code, li code, td code {
  background: rgba(255, 253, 249, 0.08);
  border: 1px solid var(--color-ash);
  border-radius: 4px;
  padding: 1px 6px;
  font-size: 0.9em;
  color: var(--color-bone);
}

::selection {
  background: rgba(242, 242, 239, 0.9);
  color: var(--color-obsidian);
}

:focus-visible {
  outline: 1px solid var(--color-bone);
  outline-offset: 3px;
}

/* --------------------------------------------------------------------------
   3. 布局工具
   -------------------------------------------------------------------------- */
.container {
  max-width: var(--page-max-width);
  margin: 0 auto;
  padding-left: var(--page-pad-x);
  padding-right: var(--page-pad-x);
}

.section { margin: var(--section-gap) 0; }

.grid-2 { display: grid; grid-template-columns: repeat(2, 1fr); gap: var(--spacing-24); }
.grid-3 { display: grid; grid-template-columns: repeat(3, 1fr); gap: var(--spacing-24); }

.center { text-align: center; }
.muted { color: var(--color-fog); }

/* --------------------------------------------------------------------------
   4. 顶部细边栏 .announce(电影感 eyebrow,非促销条)
   -------------------------------------------------------------------------- */
.announce {
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: var(--spacing-16);
  max-width: var(--page-max-width);
  margin: 0 auto;
  padding: 14px var(--page-pad-x) 0;
  color: var(--color-fog);
  font-size: var(--text-caption);
  letter-spacing: 0.04em;
  text-transform: uppercase;
}

.announce-link {
  margin-left: auto;
  color: var(--color-fog);
  text-decoration: none;
  white-space: nowrap;
  transition: color var(--dur) var(--ease);
}
.announce-link:hover { color: var(--color-bone); }

/* --------------------------------------------------------------------------
   5. 导航 .nav
   -------------------------------------------------------------------------- */
.nav {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--spacing-24);
  min-height: 84px;
  max-width: var(--page-max-width);
  margin: 0 auto;
  padding: 0 var(--page-pad-x);
  background: transparent;
}

.nav-brand {
  font-family: var(--font-sans);
  font-size: var(--text-body-lg);
  font-weight: var(--fw-medium);
  letter-spacing: -0.01em;
  color: var(--color-bone);
  text-decoration: none;
  display: inline-flex;
  align-items: center;
  gap: 10px;
  white-space: nowrap;
}

/* 品牌点:白色方块(呼应背景里的玻璃立方体,印刷式的干脆) */
.nav-dot {
  width: 10px;
  height: 10px;
  background: var(--color-bone);
  display: inline-block;
  flex: 0 0 auto;
}

.nav-links {
  display: flex;
  align-items: center;
  gap: var(--spacing-40);
}

.nav-link {
  font-size: var(--text-caption);
  text-transform: uppercase;
  letter-spacing: 0.16em;
  color: var(--color-bone);
  text-decoration: none;
  white-space: nowrap;
  transition: color var(--dur) var(--ease);
}
.nav-link:hover { color: var(--color-fog); }

/* --------------------------------------------------------------------------
   6. 按钮与链接(0px 圆角;无饱和填充;招牌缓动)
   -------------------------------------------------------------------------- */
.btn {
  position: relative;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 10px;
  font-family: var(--font-sans);
  font-size: var(--text-caption);
  font-weight: var(--fw-medium);
  text-transform: uppercase;
  letter-spacing: 0.16em;
  line-height: 1;
  padding: 15px 28px;
  border-radius: var(--radius-button);
  border: 1px solid var(--color-bone);
  background: transparent;
  color: var(--color-bone);
  cursor: pointer;
  text-decoration: none;
  white-space: nowrap;
  transition: background-color var(--dur) var(--ease),
              border-color var(--dur) var(--ease),
              color var(--dur) var(--ease);
}
.btn:hover:not(:disabled) {
  background: var(--color-bone);
  color: var(--color-obsidian);
}
.btn:disabled { cursor: default; opacity: 0.5; }

/* 主行动:实心印刷白,hover 反相为描边(Transmission 的黑白对撞) */
.btn-blue {
  background: var(--color-bone);
  border-color: var(--color-bone);
  color: var(--color-obsidian);
}
.btn-blue:hover:not(:disabled) {
  background: transparent;
  border-color: var(--color-bone);
  color: var(--color-bone);
}

/* 反相骨白填充(稀有,用于「检查答案」等) */
.btn-black {
  background: var(--color-bone);
  border-color: var(--color-bone);
  color: var(--color-obsidian);
}
.btn-black:hover:not(:disabled) {
  background: transparent;
  color: var(--color-bone);
}

/* 幽灵按钮:雾蓝描边 */
.btn-ghost {
  border-color: var(--color-ash);
  color: var(--color-bone);
  background: transparent;
}
.btn-ghost:hover:not(:disabled) {
  border-color: var(--color-bone);
  background: transparent;
  color: var(--color-bone);
}

.btn-sm { padding: 10px 18px; font-size: 13px; }

.link-arrow {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  font-size: var(--text-caption);
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--color-bone);
  text-decoration: none;
  white-space: nowrap;
  transition: gap var(--dur) var(--ease), color var(--dur) var(--ease);
}
.link-arrow:hover { gap: 14px; color: var(--color-fog); }

/* --------------------------------------------------------------------------
   7. 卡片 / 标签 / 光晕
   -------------------------------------------------------------------------- */
.card {
  position: relative;
  border: 1px solid var(--color-ash);
  border-radius: var(--radius-card);
  padding: var(--card-padding);
  background: var(--surface-1);
  transition: border-color var(--dur) var(--ease), transform var(--dur) var(--ease);
}
.card:hover { border-color: rgba(255, 253, 249, 0.32); }

.card h3 { margin-bottom: var(--spacing-16); }
.card p { color: var(--color-fog); margin-bottom: 0; }
.card p + p { margin-top: var(--spacing-16); }

/* 强调卡:graphite veil 暗化面 + 一道棱镜顶边 */
.card-peri {
  background: var(--surface-veil);
  border-color: transparent;
  overflow: hidden;
}
.card-peri::before {
  content: "";
  position: absolute;
  left: 0; right: 0; top: 0;
  height: 2px;
  background: var(--color-bone);
}
.card-peri p { color: rgba(255, 253, 249, 0.78); }

.card-icon {
  font-size: 24px;
  line-height: 1;
  display: block;
  margin-bottom: var(--spacing-16);
}

.tag {
  display: inline-flex;
  align-items: center;
  gap: var(--spacing-8);
  background: transparent;
  border: 1px solid var(--color-ash);
  border-radius: var(--radius-tag);
  padding: 6px 15px;
  font-family: var(--font-sans);
  font-size: 12px;
  font-weight: var(--fw-medium);
  text-transform: uppercase;
  letter-spacing: 0.22em;    /* 单曲封面式的撑开字距 */
  color: var(--color-fog);
  white-space: nowrap;
  text-decoration: none;
}

/* 装饰光晕:极淡的白雾(单色纪律下唯一允许的"光") */
.wash {
  position: absolute;
  left: 50%;
  top: 10%;
  transform: translateX(-50%);
  width: min(760px, 90vw);
  height: 460px;
  border-radius: 50%;
  background: radial-gradient(circle, rgba(242, 242, 239, 0.05), transparent 62%);
  filter: blur(40px);
  pointer-events: none;
  z-index: 0;
}
.wash-mint {
  background: radial-gradient(circle, rgba(242, 242, 239, 0.03), transparent 62%);
}

.hero,
.wash-host { position: relative; }
.hero > :not(.wash):not(.prism-stage),
.wash-host > :not(.wash) { position: relative; z-index: 1; }

/* --------------------------------------------------------------------------
   7.5 滚动运镜背景画布(js/prism-bg.js 注入)
   -------------------------------------------------------------------------- */
#prism-bg {
  position: fixed;
  inset: 0;
  width: 100%;
  height: 100%;
  z-index: -1;
  opacity: 0;
  transition: opacity 1.4s var(--ease);
  pointer-events: none;
  object-fit: contain;          /* 整幅可见,永不裁切 */
  background: #000;             /* 信箱边与视频底色同为纯黑(纯黑经 AgX/H.264 精确保 0)→ 无缝 */
}
#prism-bg.is-live { opacity: 1; }
/* 课程页:背景视频亮度减半(透明视频上 opacity 与黑底混合 = 等效减亮,零滤镜开销) */
body:not(.home) #prism-bg.is-live { opacity: 0.5; }

/* 卡片:微透明近黑(不用 backdrop-filter,滚动零重绘代价),让方块隐约透出又保证可读 */
.card,
.quiz,
.stepper-panel,
.progress-board {
  background: rgba(4, 4, 4, 0.82);
}
.card-peri {
  background: rgba(14, 14, 14, 0.9);
}

/* --------------------------------------------------------------------------
   8. 棱镜招牌构件 .prism + Hero
   -------------------------------------------------------------------------- */
.prism-stage {
  position: relative;
  display: flex;
  justify-content: center;
  z-index: 0;
  margin: 0 auto;
  pointer-events: none;
}
.prism {
  width: min(560px, 84vw);
  height: auto;
  display: block;
  filter: drop-shadow(0 30px 80px rgba(0, 0, 0, 0.6));
}

/* 色散幽灵层的缓慢漂移(kVfqLU,6.65s):三通道各自错位游走 */
.prism-ghost { transform-box: fill-box; transform-origin: center; }
.prism-ghost-r { animation: prism-shift-r 6.65s var(--ease) infinite alternate; }
.prism-ghost-b { animation: prism-shift-b 6.65s var(--ease) infinite alternate; }
.prism-ghost-g { animation: prism-shift-g 6.65s var(--ease) infinite alternate; }

@keyframes prism-shift-r {
  0%   { transform: translate(-3px, -2px); }
  100% { transform: translate(4px, 3px); }
}
@keyframes prism-shift-b {
  0%   { transform: translate(3px, 1px); }
  100% { transform: translate(-4px, -2px); }
}
@keyframes prism-shift-g {
  0%   { transform: translate(1px, 3px); }
  100% { transform: translate(-2px, -4px); }
}

.hero {
  text-align: center;
  padding: var(--spacing-56) 0 var(--spacing-64);
  /* 3D 运镜背景当主角:首屏留足舞台,文字悬浮其上 */
  min-height: 78vh;
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
}
.hero .prism-stage { margin-bottom: calc(-1 * var(--spacing-56)); }

/* Hero 载入:骨白元素依次上浮淡入(招牌缓动) */
.hero .prism-stage { animation: hero-in 1s var(--ease) both; }
.hero-title { animation: hero-in 0.9s var(--ease) 0.12s both; }
.hero-sub { animation: hero-in 0.9s var(--ease) 0.24s both; }
.hero-actions { animation: hero-in 0.9s var(--ease) 0.36s both; }
@keyframes hero-in {
  0% { opacity: 0; transform: translateY(26px); }
  100% { opacity: 1; transform: none; }
}

.hero-title {
  font-size: var(--text-display);
  font-weight: var(--fw-display-cjk);
  line-height: 1.0;
  letter-spacing: 0.04em;    /* Transmission:字距撑开,像封面排版 */
  margin: 0 auto var(--spacing-24);
  max-width: 14em;
}

.hero-sub {
  font-size: var(--text-body-lg);
  font-weight: var(--fw-regular);
  color: var(--color-fog);
  line-height: 1.5;
  max-width: 46ch;
  margin: 0 auto var(--spacing-40);
}

.hero-actions {
  display: flex;
  justify-content: center;
  gap: var(--spacing-16);
  flex-wrap: wrap;
}

/* 课程页头 */
.lesson-header { padding: var(--spacing-64) 0 var(--spacing-24); }
.lesson-header .tag { margin-bottom: var(--spacing-24); }
.lesson-intro {
  font-size: var(--text-body-lg);
  color: var(--color-fog);
  line-height: 1.5;
  max-width: 54ch;
}

/* --------------------------------------------------------------------------
   9. FAQ 手风琴 .faq-item
   -------------------------------------------------------------------------- */
.faq-item { border-bottom: 1px solid var(--color-ash); }

.faq-item summary {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--spacing-24);
  padding: var(--spacing-40) 0;
  cursor: pointer;
  font-family: var(--font-sans);
  font-size: var(--text-heading-sm);
  font-weight: var(--fw-regular);
  letter-spacing: -0.02em;
  color: var(--color-bone);
  list-style: none;
  transition: color var(--dur) var(--ease);
}
.faq-item summary:hover { color: var(--color-fog); }
.faq-item summary::-webkit-details-marker { display: none; }

.faq-item summary::after {
  content: "+";
  font-family: var(--font-mono);
  font-size: 28px;
  font-weight: 300;
  line-height: 1;
  flex: 0 0 auto;
  color: var(--color-fog);
  transition: transform var(--dur) var(--ease), color var(--dur) var(--ease);
}
.faq-item[open] summary { color: var(--color-bone); }
.faq-item[open] summary::after { transform: rotate(45deg); color: var(--color-bone); }

.faq-body {
  padding: 0 0 var(--spacing-40);
  max-width: 68ch;
  color: var(--color-fog);
  font-size: var(--text-body-sm);
  line-height: 1.6;
}

/* --------------------------------------------------------------------------
   10. 课程路径图 .pipeline
   -------------------------------------------------------------------------- */
.pipeline {
  display: flex;
  align-items: center;
  gap: 4px;
  overflow-x: auto;
  padding: var(--spacing-24) 2px;
  -webkit-overflow-scrolling: touch;
  scrollbar-width: thin;
}
.pipeline > * { flex: 0 0 auto; }
.pipeline svg { display: block; color: var(--color-ash); }

/* --------------------------------------------------------------------------
   10.2 双模式(蓝图 / C++):.m-bp 与 .m-cpp 按 html[data-mode] 显隐
   无 JS / 未设定时默认展示 C++ 版(与现有内容一致的降级)
   -------------------------------------------------------------------------- */
.m-bp { display: none; }
html[data-mode="bp"] .m-bp { display: revert; }
html[data-mode="bp"] .m-cpp { display: none; }
/* span 级内联变体在 revert 下回到 inline;块级(p/div/section/table)同理回归各自默认 */

/* 导航分段切换器(左上角,品牌旁) */
.mode-switch {
  display: inline-flex;
  border: 1px solid var(--color-ash);
  margin-left: 18px;
  flex: 0 0 auto;
}
.mode-seg {
  font-family: var(--font-sans);
  font-size: 12px;
  text-transform: uppercase;
  letter-spacing: 0.14em;
  padding: 6px 14px;
  background: transparent;
  border: none;
  color: var(--color-fog);
  cursor: pointer;
  transition: background-color var(--dur-fast) var(--ease), color var(--dur-fast) var(--ease);
}
.mode-seg + .mode-seg { border-left: 1px solid var(--color-ash); }
.mode-seg.is-on {
  background: var(--color-bone);
  color: var(--color-obsidian);
}
.mode-seg:not(.is-on):hover { color: var(--color-bone); }

/* 首访询问弹窗:全屏纯黑,印刷排版 */
.mode-modal {
  position: fixed;
  inset: 0;
  z-index: 100;
  background: rgba(0, 0, 0, 0.96);
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 24px;
}
.mode-modal-box {
  max-width: 720px;
  width: 100%;
  border: 1px solid var(--color-ash);
  background: #000;
  padding: 48px 40px;
  text-align: center;
}
.mode-modal-eyebrow {
  font-size: 12px;
  letter-spacing: 0.3em;
  text-transform: uppercase;
  color: var(--color-fog);
  margin: 0 0 18px;
}
.mode-modal-title {
  font-size: var(--text-heading);
  margin: 0 0 10px;
}
.mode-modal-sub {
  color: var(--color-fog);
  font-size: var(--text-body-sm);
  margin: 0 0 32px;
}
.mode-modal-actions {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--spacing-16);
  text-align: left;
}
.mode-modal-btn {
  font-family: var(--font-sans);
  background: transparent;
  border: 1px solid var(--color-ash);
  color: var(--color-bone);
  padding: 22px 20px;
  cursor: pointer;
  transition: border-color var(--dur-fast) var(--ease), background-color var(--dur-fast) var(--ease);
}
.mode-modal-btn:hover {
  border-color: var(--color-bone);
  background: rgba(242, 242, 239, 0.05);
}
.mode-modal-btn-title {
  display: block;
  font-size: var(--text-body-lg);
  margin-bottom: 8px;
}
.mode-modal-btn-sub {
  display: block;
  font-size: 14px;
  line-height: 1.55;
  color: var(--color-fog);
}
@media (max-width: 700px) {
  .mode-modal-actions { grid-template-columns: 1fr; }
  .mode-modal-box { padding: 32px 22px; }
  .mode-switch { margin-left: 10px; }
  .mode-seg { padding: 5px 10px; font-size: 11px; }
}

/* --------------------------------------------------------------------------
   10.25 账号 / 登录(auth.js 注入)
   -------------------------------------------------------------------------- */
/* 课程页鉴权前先藏正文,避免受限内容闪现 */
html.vw-checking main { visibility: hidden; }

.auth-control { position: relative; display: inline-flex; }
.account-btn { font-variant-numeric: tabular-nums; }
.account-menu {
  position: absolute;
  top: calc(100% + 8px);
  right: 0;
  min-width: 200px;
  background: #000;
  border: 1px solid var(--color-ash);
  padding: 14px 16px;
  display: flex;
  flex-direction: column;
  gap: 8px;
  z-index: 40;
}
.account-email { font-size: 13px; color: var(--color-bone); word-break: break-all; }
.account-tier {
  font-size: 11px; letter-spacing: 0.12em; text-transform: uppercase; color: var(--color-fog);
  padding-bottom: 8px; border-bottom: 1px solid var(--color-ash);
}
.account-logout {
  font-family: var(--font-sans); font-size: 13px; text-align: left;
  background: transparent; border: none; color: var(--color-bone); cursor: pointer; padding: 2px 0;
}
.account-logout:hover { color: var(--color-fog); }

/* 登录 / 门禁弹窗 */
.auth-modal {
  position: fixed; inset: 0; z-index: 100;
  background: rgba(0, 0, 0, 0.96);
  display: flex; align-items: center; justify-content: center; padding: 24px;
}
/* 落地在受限课程页的持久门禁:全不透明,内容不可窥视 */
.auth-modal.auth-persist { background: #000; }
.auth-box {
  position: relative;
  max-width: 460px; width: 100%;
  border: 1px solid var(--color-ash); background: #000;
  padding: 40px 34px; text-align: center;
}
.auth-close {
  position: absolute; top: 14px; right: 16px;
  background: transparent; border: none; color: var(--color-fog);
  font-size: 18px; cursor: pointer; line-height: 1;
}
.auth-close:hover { color: var(--color-bone); }
.auth-eyebrow { font-size: 12px; letter-spacing: 0.3em; text-transform: uppercase; color: var(--color-fog); margin: 0 0 16px; }
.auth-title { font-size: var(--text-heading-sm); margin: 0 0 10px; }
.auth-sub { color: var(--color-fog); font-size: var(--text-body-sm); line-height: 1.55; margin: 0 0 26px; }
.auth-step { display: flex; flex-direction: column; gap: 12px; }
.auth-input {
  font-family: var(--font-mono); font-size: 16px;
  background: transparent; border: 1px solid var(--color-ash); color: var(--color-bone);
  padding: 13px 14px; text-align: center; border-radius: 0;
}
.auth-input:focus { outline: none; border-color: var(--color-bone); }
.auth-code { letter-spacing: 0.4em; }
.auth-code-to { font-size: 13px; margin: 0 0 2px; }
.auth-linkbtn {
  font-family: var(--font-sans); font-size: 13px;
  background: transparent; border: none; color: var(--color-fog); cursor: pointer;
  text-decoration: none; display: inline-block; margin-top: 4px;
}
.auth-linkbtn:hover { color: var(--color-bone); }
.auth-home { margin-top: 22px; }
.auth-msg { font-size: 13px; line-height: 1.5; margin: 16px 0 0; min-height: 1em; color: var(--color-fog); }
.auth-msg:empty { margin: 0; }
.auth-msg-err { color: var(--color-no-text); }
.auth-msg-test { color: var(--color-ok-text); font-family: var(--font-mono); }

@media (max-width: 700px) {
  .auth-box { padding: 30px 20px; }
  .account-menu { right: auto; left: 0; }
}

/* --------------------------------------------------------------------------
   10.3 课程地图:7 章 23 课紧凑行(印刷目录感)
   -------------------------------------------------------------------------- */
.chapters {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: var(--spacing-16);
}
.chapter {
  border: 1px solid var(--color-ash);
  padding: var(--spacing-16) var(--spacing-20);
  background: rgba(4, 4, 4, 0.82);
}
.chapter-head { margin: 0 0 10px; }
.chapter-list {
  list-style: none;
  margin: 0;
  padding: 0;
}
.chapter-list li { margin: 0; }
.lesson-row {
  display: flex;
  align-items: baseline;
  gap: 14px;
  padding: 7px 4px;
  text-decoration: none;
  border-bottom: 1px solid rgba(242, 242, 239, 0.07);
  transition: background-color var(--dur-fast) var(--ease);
  position: relative;
}
.chapter-list li:last-child .lesson-row { border-bottom: none; }
.lesson-row:hover { background: rgba(242, 242, 239, 0.06); }
.lesson-no {
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.14em;
  color: var(--color-fog);
  flex: 0 0 auto;
}
.lesson-name {
  font-size: var(--text-body-sm);
  color: var(--color-bone);
}
.lesson-row .done-badge {
  position: static;
  margin-left: auto;
  align-self: center;
}

@media (max-width: 900px) {
  .chapters { grid-template-columns: 1fr; }
}

/* --------------------------------------------------------------------------
   10.5 波形线(Transmission 印刷波形:hero 脉冲星波群 + 板块分隔波线)
   -------------------------------------------------------------------------- */
.hero-wave {
  display: block;
  width: min(620px, 86vw);
  height: auto;
  margin: 0 auto var(--spacing-40);
  color: var(--color-bone);
  opacity: 0.9;
  animation: hero-in 0.9s var(--ease) 0.3s both;
}

/* 课程页:板块之间的正弦细波分隔线 */
body:not(.home) main .section + .section::before {
  content: "";
  display: block;
  height: 14px;
  margin-bottom: var(--spacing-56);
  background: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='120' height='14' viewBox='0 0 120 14'%3E%3Cpath d='M0 7 Q15 0 30 7 T60 7 T90 7 T120 7' fill='none' stroke='%23f2f2ef' stroke-opacity='.3' stroke-width='1'/%3E%3C/svg%3E") repeat-x left center;
  background-size: 120px 14px;
}

/* --------------------------------------------------------------------------
   11. 页脚 .footer
   -------------------------------------------------------------------------- */
.footer {
  border-top: 1px solid var(--color-ash);
  margin-top: var(--spacing-108);
}
.footer-inner {
  max-width: var(--page-max-width);
  margin: 0 auto;
  padding: var(--spacing-40) var(--page-pad-x);
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: var(--spacing-16);
  font-size: var(--text-caption);
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--color-fog);
}
.footer a { color: inherit; transition: color var(--dur) var(--ease); }
.footer a:hover { color: var(--color-bone); }

/* --------------------------------------------------------------------------
   12. 代码块 + Verse 语法高亮(棱镜色散在此落地:代码即被折射的光)
   -------------------------------------------------------------------------- */
.code-block {
  margin: var(--spacing-24) 0;
  background: var(--code-bg);
  border: 1px solid var(--code-border);
  border-radius: var(--radius-code);
  overflow: hidden;
}
.code-title {
  font-family: var(--font-mono);
  font-size: 13px;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--color-fog);
  padding: 12px 22px;
  border-bottom: 1px solid var(--code-border);
}
.code-block pre { margin: 0; padding: 20px 22px; overflow-x: auto; }
.code-block code {
  display: block;
  font-family: var(--font-mono);
  font-size: 14.5px;
  line-height: 1.75;
  color: var(--code-fg);
  white-space: pre;
  background: transparent;
  border: none;
  padding: 0;
}

.code-line {
  display: inline-block;
  min-width: calc(100% + 44px);
  margin: 0 -22px;
  padding: 0 22px;
  transition: background-color var(--dur-fast) var(--ease);
}
.line-active {
  background: rgba(242, 242, 239, 0.09);
  box-shadow: inset 3px 0 0 var(--color-bone);
}

/* token 颜色:纯灰阶层次(明度 + 字重 + 斜体做区分,代码即黑白印刷) */
.tok-kw      { color: #ffffff; font-weight: 600; }
.tok-string  { color: #b4b4b0; }
.tok-interp  { color: #e6e6e2; }
.tok-comment { color: #565654; font-style: italic; }
.tok-type    { color: #d2d2ce; }
.tok-num     { color: #dcdcd8; }
.tok-spec    { color: #90908c; font-style: italic; }
.tok-attr    { color: #90908c; }
.tok-fn      { color: #ededea; }

/* --------------------------------------------------------------------------
   13. 选择题测验 .quiz
   -------------------------------------------------------------------------- */
.quiz {
  border: 1px solid var(--color-ash);
  border-radius: var(--radius-card);
  padding: var(--spacing-24);
  margin: var(--spacing-24) 0;
  background: var(--surface-1);
}
.quiz-q {
  font-size: var(--text-body);
  font-weight: var(--fw-medium);
  color: var(--color-bone);
  margin: 0 0 var(--spacing-16);
}
.quiz-opts { display: flex; flex-direction: column; gap: 10px; }
.quiz-opt {
  display: block;
  width: 100%;
  text-align: left;
  font-family: var(--font-sans);
  font-size: var(--text-body-sm);
  color: var(--color-bone);
  background: transparent;
  border: 1px solid var(--color-ash);
  border-radius: var(--radius-button);
  padding: 14px 20px;
  cursor: pointer;
  transition: border-color var(--dur-fast) var(--ease), background-color var(--dur-fast) var(--ease), color var(--dur-fast) var(--ease);
}
.quiz-opt:hover:not(:disabled) { border-color: var(--color-bone); }
.quiz-opt:disabled { cursor: default; opacity: 0.55; }
.quiz-opt.is-ok {
  background: var(--color-ok-bg);
  border-color: var(--color-ok-border);
  color: var(--color-ok-text);
  opacity: 1;
}
.quiz-opt.is-no {
  background: var(--color-no-bg);
  border-color: var(--color-no-border);
  color: var(--color-no-text);
}
.quiz-fb { margin: var(--spacing-16) 0 0; font-size: var(--text-body-sm); }
.quiz-fb:empty { display: none; }
.quiz-fb.is-ok { color: var(--color-ok-text); }
.quiz-fb.is-no { color: var(--color-no-text); }

/* --------------------------------------------------------------------------
   14. 代码填空 .fill
   -------------------------------------------------------------------------- */
.fill { margin: var(--spacing-40) 0; }
.blank {
  color: #e6e6e2;
  border-bottom: 1px dashed #e6e6e2;
  font-weight: 400;
  font-style: normal;
}
.blank-input {
  font-family: var(--font-mono);
  font-size: 14.5px;
  line-height: 1.4;
  background: transparent;
  border: none;
  border-bottom: 1px dashed #e6e6e2;
  color: #e6e6e2;
  text-align: center;
  padding: 0 2px;
  border-radius: 0;
}
.blank-input:focus { border-bottom-style: solid; }
.blank-input:focus-visible { outline: 1px solid var(--color-bone); outline-offset: 2px; }
.blank-input:disabled { opacity: 1; }
.blank-input.is-ok { border-bottom: 1px solid var(--color-ok-text); color: var(--color-ok-text); }
.blank-input.is-no {
  border-bottom: 1px solid var(--color-no-text);
  color: var(--color-no-text);
  animation: blank-shake 0.3s var(--ease);
}
@keyframes blank-shake {
  0%, 100% { transform: translateX(0); }
  25% { transform: translateX(-3px); }
  75% { transform: translateX(3px); }
}
.fill-bar {
  display: flex;
  align-items: center;
  gap: var(--spacing-16);
  margin-top: var(--spacing-16);
  flex-wrap: wrap;
}
.fill-fb { font-size: var(--text-body-sm); }
.fill-fb:empty { display: none; }
.fill-fb.is-ok { color: var(--color-ok-text); }
.fill-fb.is-no { color: var(--color-no-text); }

/* --------------------------------------------------------------------------
   15. 代码步进器 .stepper
   -------------------------------------------------------------------------- */
.stepper {
  display: grid;
  grid-template-columns: 3fr 2fr;
  gap: var(--spacing-24);
  align-items: start;
  margin: var(--spacing-40) 0;
}
.stepper .code-block { margin: 0; }
.stepper-panel {
  border: 1px solid var(--color-ash);
  border-radius: var(--radius-card);
  padding: var(--spacing-24);
  background: var(--surface-1);
  display: flex;
  flex-direction: column;
  gap: var(--spacing-16);
}
.stepper-scene {
  font-size: 48px;
  line-height: 1;
  min-height: 56px;
}
.stepper-scene.is-pop { animation: scene-fade var(--dur) var(--ease); }
@keyframes scene-fade {
  0%   { opacity: 0.2; transform: translateY(6px); }
  100% { opacity: 1; transform: translateY(0); }
}
.stepper-log {
  background: var(--code-bg);
  border: 1px solid var(--code-border);
  border-radius: 10px;
  padding: var(--spacing-16);
  display: flex;
  flex-direction: column;
  gap: 10px;
  min-height: 96px;
}
.stepper-log .tag { align-self: flex-start; }
.stepper-log-lines {
  display: flex;
  flex-direction: column;
  gap: 6px;
  font-family: var(--font-mono);
  font-size: 13px;
  color: #d6d6d2;
}
.stepper-log-line { white-space: pre-wrap; word-break: break-all; }
.stepper-note {
  font-size: var(--text-body-sm);
  color: var(--color-fog);
  line-height: 1.5;
  margin: 0;
  min-height: 3em;
}
.stepper-ctrl { display: flex; gap: 12px; flex-wrap: wrap; }

/* --------------------------------------------------------------------------
   16. 进度、星星与完成按钮
   -------------------------------------------------------------------------- */
.progress-board {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: var(--spacing-16);
  text-align: center;
  margin: var(--spacing-40) auto;
  padding: var(--spacing-40);
  border: 1px solid var(--color-ash);
  border-radius: var(--radius-card);
  background: var(--surface-1);
  max-width: 720px;
}
.progress-cells { display: flex; gap: var(--spacing-8); flex-wrap: wrap; justify-content: center; }
.progress-cell {
  display: inline-block;
  width: 46px;
  height: 8px;
  border-radius: var(--radius-tag);
  border: 1px solid var(--color-ash);
  background: transparent;
  transition: background-color var(--dur) var(--ease), border-color var(--dur) var(--ease);
}
.progress-cell.is-done {
  background: var(--color-bone);
  border-color: var(--color-bone);
}
.progress-text {
  display: flex;
  gap: var(--spacing-24);
  justify-content: center;
  flex-wrap: wrap;
  font-size: var(--text-body-sm);
  color: var(--color-bone);
  margin: 0;
}
.progress-stars { white-space: nowrap; }

.done-badge {
  position: absolute;
  top: var(--spacing-16);
  right: var(--spacing-16);
  background: transparent;
  border: 1px solid var(--color-ok-border);
  color: var(--color-ok-text);
  border-radius: var(--radius-tag);
  font-size: 12px;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  padding: 4px 12px;
}

.lesson-complete.is-done {
  background: var(--color-ok-bg);
  border-color: var(--color-ok-border);
  color: var(--color-ok-text);
  opacity: 1;
  cursor: default;
}
.lesson-complete.is-done::after { opacity: 0; }

.fill-check, .stepper-next, .stepper-reset, .reset-progress {
  font-family: var(--font-sans);
  cursor: pointer;
}

/* --------------------------------------------------------------------------
   17. 课程页导航
   -------------------------------------------------------------------------- */
.lesson-nav {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--spacing-16);
  flex-wrap: wrap;
  margin-top: var(--spacing-64);
  padding-top: var(--spacing-40);
  border-top: 1px solid var(--color-ash);
}

/* --------------------------------------------------------------------------
   18. 滚动揭示(transform + opacity,招牌缓动)
   -------------------------------------------------------------------------- */
/* 隐藏态仅在 JS 就绪(html.reveal-ready)后生效 —— JS 失败则内容照常可见 */
.reveal-ready [data-reveal] {
  opacity: 0;
  transform: translateY(22px);
  transition: opacity 0.7s var(--ease), transform 0.7s var(--ease);
  will-change: opacity, transform;
}
.reveal-ready [data-reveal].is-in { opacity: 1; transform: none; }

/* --------------------------------------------------------------------------
   18.5 整屏分页:首页每个板块占满一屏,吸附翻页,一次只见一个板块
   背景动画随之按板块切换运镜节拍。
   -------------------------------------------------------------------------- */
body.home main > .section {
  margin: 0;               /* 取消板块间 margin,避免破坏吸附与"占满一屏" */
}
body.home .hero,
body.home main > .section {
  min-height: 100vh;
  min-height: 100svh;      /* 移动端避开地址栏抖动 */
  display: flex;
  flex-direction: column;
  justify-content: center;
  scroll-snap-align: start;
  /* 不用 snap-stop:always —— 否则会卡住,顶部/底部滚不到 */
  padding-top: var(--spacing-72);
  padding-bottom: var(--spacing-72);
}
/* 首页:eyebrow 藏起(内容已在 hero 里),导航固定常驻 → 顶部永远可见 */
body.home .announce { display: none; }
body.home .nav {
  position: fixed;
  top: 0; left: 0; right: 0;
  z-index: 30;
  background: linear-gradient(to bottom, rgba(0, 0, 0, 0.82), rgba(0, 0, 0, 0));
}
/* 首屏板块给固定导航让出高度,避免标题被压在导航下 */
body.home .hero { padding-top: 104px; }
/* 页脚设为末端吸附点 → 滚到底能停在页脚,底部可正常显示 */
body.home .footer {
  scroll-snap-align: end;
  margin-top: 0;
}
html:has(body.home) {
  scroll-snap-type: y mandatory;
  scroll-padding-top: 88px;   /* 锚点跳转为固定导航留位 */
}

@media (prefers-reduced-motion: reduce) {
  html:has(body.home) { scroll-snap-type: none; }
}

/* 课程板块紧凑化:8 张卡挤进一屏(桌面 4 列 2 行,隐藏路径图省纵向空间) */
body.home #lessons > p { margin-bottom: var(--spacing-16); }
body.home #lessons .pipeline { display: none; }
body.home #lessons .grid-2 {
  grid-template-columns: repeat(4, 1fr);
  gap: var(--spacing-16);
}
body.home #lessons .card { padding: 18px; }
body.home #lessons .card .tag { padding: 4px 10px; font-size: 11px; }
body.home #lessons .card h3 { margin: 10px 0 8px; font-size: var(--text-body-lg); }
body.home #lessons .card p { font-size: 14px; line-height: 1.45; margin-bottom: 12px; }
body.home #lessons .card .link-arrow { font-size: 13px; }

@media (max-width: 1080px) {
  body.home #lessons .grid-2 { grid-template-columns: repeat(2, 1fr); }
}
@media (max-width: 600px) {
  body.home #lessons .grid-2 { grid-template-columns: 1fr; }
  /* 窄屏放弃强制整屏,回归自然滚动阅读 */
  html:has(body.home) { scroll-snap-type: none; }
  body.home .hero,
  body.home main > .section { min-height: auto; padding-top: var(--spacing-56); padding-bottom: var(--spacing-56); }
  body.home #lessons .pipeline { display: flex; }
}

/* --------------------------------------------------------------------------
   19. 响应式断点
   -------------------------------------------------------------------------- */
@media (max-width: 1080px) {
  .grid-3 { grid-template-columns: repeat(2, 1fr); }
}
@media (max-width: 900px) {
  .grid-2, .grid-3 { grid-template-columns: 1fr; }
  .stepper { grid-template-columns: 1fr; }
  .nav .nav-link { display: none; }
  .nav .nav-links .btn { display: inline-flex; }
  .nav { min-height: 68px; }
  .btn { padding: 13px 22px; }
  .hero { padding: var(--spacing-40) 0 var(--spacing-56); }
  .code-block pre { padding: 16px 18px; }
  .code-line { min-width: calc(100% + 36px); margin: 0 -18px; padding: 0 18px; }
  .faq-item summary { padding: var(--spacing-24) 0; }
  .progress-board { padding: var(--spacing-24); }
}

/* --------------------------------------------------------------------------
   20. 无障碍:减弱动态效果
   -------------------------------------------------------------------------- */
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
  }
  [data-reveal] { opacity: 1 !important; transform: none !important; }
}