:root {
  --bg: #f5f5f7;
  --card: #ffffff;
  --ink: #1a1a1a;
  --muted: #6b6b73;          /* WCAG AA: 5.1:1 on bg, 5.5:1 on card (was #86868b = 3.3:1) */
  --accent: #ee5f00;         /* brand fill; white text on it = 3.35:1 (passes UI 3:1) */
  --accent-strong: #c25200;  /* hover/active fill */
  --accent-text: #c25200;    /* named alias: use for any accent-coloured *text* */
  --accent-soft: #fff3eb;
  --line: #e3e3e9;
  --code-bg: #101014;
  --code-ink: #e8e8ed;
  --ok: #14754a;             /* AA: 4.8:1 on card (was #1a9c5d = 3.5:1) */
  --err: #c02b21;            /* AA: 5.3:1 on card */
  --header-bg: rgba(255, 255, 255, 0.9);
  --shadow-sm: 0 2px 10px rgba(0, 0, 0, 0.04);
  --shadow-md: 0 4px 20px rgba(0, 0, 0, 0.08);
  --chip-bg: #f2f2f5;
  --chip-ink: #55555c;
  --tok-c: #8b8b93;   /* comments */
  --tok-k: #ff9760;   /* keywords */
  --tok-s: #8fd3a7;   /* strings */
  --tok-n: #7db8ff;   /* numbers */
  --tok-p: #e8b16a;   /* preprocessor */
  --tok-sd: #b6a5f2;  /* std names */

  /* ---- spacing scale (4px grid) ---- */
  --sp-1: 4px;
  --sp-2: 8px;
  --sp-3: 12px;
  --sp-4: 16px;
  --sp-5: 20px;
  --sp-6: 24px;
  --sp-7: 32px;
  --sp-8: 40px;
  --sp-9: 56px;

  /* ---- type scale ---- */
  --fs-xs: 12px;
  --fs-sm: 13.5px;
  --fs-base: 15.5px;
  --fs-md: 17px;
  --fs-lg: 21px;
  --fs-xl: 27px;
  --fs-2xl: 34px;

  /* ---- radii ---- */
  --r-sm: 8px;
  --r-md: 12px;
  --r-lg: 16px;
  --r-pill: 999px;

  color-scheme: light;
}

:root[data-theme="dark"] {
  --bg: #0e0e10;
  --card: #1a1a1d;
  --ink: #f2f2f4;
  --muted: #9a9aa2;
  --accent: #ff8a3d;
  --accent-strong: #ffa05e;
  --accent-text: #ffab73;
  --accent-soft: rgba(255, 105, 0, 0.14);
  --line: #2a2a2e;
  --code-bg: #101014;
  --code-ink: #e8e8ed;
  --ok: #4cc38a;
  --err: #ff6b61;
  --header-bg: rgba(14, 14, 16, 0.88);
  --shadow-sm: 0 2px 10px rgba(0, 0, 0, 0.35);
  --shadow-md: 0 4px 24px rgba(0, 0, 0, 0.45);
  --chip-bg: #26262a;
  --chip-ink: #c9c9cf;
  color-scheme: dark;
}

* { box-sizing: border-box; }

body {
  margin: 0;
  font-family: system-ui, -apple-system, "Segoe UI", Roboto, "MiSans", "Helvetica Neue", Arial, sans-serif;
  color: var(--ink);
  background: var(--bg);
  line-height: 1.7;
  transition: background-color 0.2s ease, color 0.2s ease;
}

::selection { background: rgba(255, 105, 0, 0.22); }

:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; }

.wrap { max-width: 1000px; margin: 0 auto; padding: 0 20px; }

/* ---------- nav ---------- */
header.site {
  background: var(--header-bg);
  -webkit-backdrop-filter: blur(16px);
  backdrop-filter: blur(16px);
  border-bottom: 1px solid var(--line);
  position: sticky;
  top: 0;
  z-index: 10;
}
.nav {
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 12px 20px;
  max-width: 1000px;
  margin: 0 auto;
  white-space: nowrap;
  /* 这里曾经有 overflow-x:auto。它不只是"允许横向滚动" —— overflow 一旦不是
     visible,就会成为滚动容器,把语言菜单的绝对定位下拉面板裁掉(只剩一条边)。
     导航宽度问题现在由汉堡菜单解决,不需要滚动容器了。 */
}
.brand {
  font-weight: 800;
  font-size: 18px;
  color: var(--ink);
  text-decoration: none;
  margin-right: 14px;
  letter-spacing: -0.01em;
}
.brand::before {
  content: "</>";
  font-family: ui-monospace, SFMono-Regular, Consolas, monospace;
  font-weight: 800;
  font-size: 12px;
  background: var(--accent);
  color: #fff;
  border-radius: 8px;
  padding: 3px 8px;
  margin-right: 8px;
  display: inline-block;
  transform: translateY(-1px);
}
.nav a.link {
  color: var(--muted);
  text-decoration: none;
  font-size: 14px;
  padding: 8px 12px;
  border-radius: 999px;
}
.nav a.link:hover { color: var(--ink); background: var(--chip-bg); }
.nav a.link.active { color: var(--ink); background: var(--chip-bg); font-weight: 600; }

/* 导航链接容器:桌面就是一行 chip,窄屏变成下拉面板(见下方 media query) */
.nav-links {
  display: flex;
  align-items: center;
  gap: 8px;
}

/* 汉堡按钮:桌面隐藏,窄屏出现。用三条 span 画,不依赖 emoji 字体 */
.nav-toggle {
  display: none;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 4px;
  width: 38px;
  height: 34px;
  padding: 0;
  border: 1px solid var(--line);
  background: var(--card);
  border-radius: 12px;
  cursor: pointer;
}
.nav-toggle .bar {
  display: block;
  width: 16px;
  height: 2px;
  border-radius: 8px;
  background: var(--ink);
  transition: transform 0.18s ease, opacity 0.12s ease;
}
.nav-toggle:hover { border-color: var(--accent-text); }
.nav.nav-open .nav-toggle { border-color: var(--accent-text); }
.nav.nav-open .nav-toggle .bar:nth-child(1) { transform: translateY(6px) rotate(45deg); }
.nav.nav-open .nav-toggle .bar:nth-child(2) { opacity: 0; }
.nav.nav-open .nav-toggle .bar:nth-child(3) { transform: translateY(-6px) rotate(-45deg); }

/* 窄屏:三语导航的自然宽度最宽 757px(西语),所以 800px 以下一律收进下拉。
   以前这里靠 overflow-x:auto,360px 手机上 738px 的内容有一半藏在横向滚动里,
   而且没有任何提示 —— 现在改成汉堡按钮 + 全宽面板,一屏看全,点击区域也够大。 */
@media (max-width: 799px) {
  .nav {
    gap: 4px;
    padding: 12px 14px;
    overflow: visible;      /* 下拉面板不能被裁掉 */
    white-space: normal;
  }
  .nav .brand { flex: 0 0 auto; margin-right: 8px; }
  .nav-toggle { display: inline-flex; }
  .nav-links {
    position: absolute;
    top: 100%;
    left: 0;
    right: 0;
    display: none;
    flex-direction: column;
    align-items: stretch;
    gap: 2px;
    padding: 8px 12px 12px;
    background: var(--card);
    border-bottom: 1px solid var(--line);
    box-shadow: var(--shadow-md);
  }
  .nav.nav-open .nav-links { display: flex; }
  .nav.nav-open .nav-links a.link {
    display: block;
    padding: 12px 14px;
    border-radius: 12px;
    font-size: 16px;
  }
}

/* 宽表格(文章里的对比表):由 site.js 的 wrapTables() 包一层滚动容器。
   四列西语表在 320px 下 min-content 有 473px —— 不包的话整页横向滚动。
   注意不能用 `table{display:block;overflow-x:auto}` 取巧:那会丢掉圆角边框,
   而且 overflow-wrap:anywhere 会把 "compilación" 拆成 "comp ilació n"。
   滚动条本身留作"右边还有列"的提示,所以别把它藏起来。 */
.table-scroll { overflow-x: auto; -webkit-overflow-scrolling: touch; }
.table-scroll > table { margin: 16px 0; }
.table-scroll::-webkit-scrollbar { height: 6px; }
.table-scroll::-webkit-scrollbar-thumb { background: var(--line); border-radius: 999px; }
.table-scroll::-webkit-scrollbar-track { background: transparent; }

/* 320px 下西语首页的示例下拉框会顶出屏幕 13px:<select> 的 min-content 宽度
   等于最长选项("Elige un ejemplo…"),而 flex 子项默认 min-width:auto 不许收缩。
   让它独占一行并允许收缩。 */
@media (max-width: 480px) {
  .toolbar select { flex: 1 1 100%; min-width: 0; max-width: 100%; }
}

/* 320–374px 的窄屏:把右侧三个控件再收一点,保证 320px 也不横向溢出 */@media (max-width: 374px) {
  .nav { padding: 8px 12px; gap: 3px; }
  .nav .brand { font-size: 16px; margin-right: 2px; }
  .nav .brand::before { margin-right: 8px; }
  .nav .lang-menu-trigger { padding: 8px 12px; font-size: 13px; }
  .nav-toggle { width: 34px; height: 32px; }
  .nav .theme-toggle { padding: 8px 8px; }
}

/* ---------- layout ---------- */
@keyframes fadeUp { from { opacity: 0; transform: translateY(6px); } to { opacity: 1; transform: none; } }
main { padding: 32px 0 64px; animation: fadeUp 0.3s ease both; }
h1 { font-size: 30px; line-height: 1.25; margin: 12px 0 8px; letter-spacing: -0.02em; font-weight: 800; }
h2 { font-size: 21px; margin-top: 36px; letter-spacing: -0.01em; font-weight: 700; }
h3 { font-size: 16px; margin-top: 24px; }
.tagline { color: var(--muted); margin: 0 0 20px; font-size: 17px; }
/* 一句话答案：给 AI 抽取用的可引用短句，同时也让人一眼扫到重点。
   刻意做成"引用块"而不是"提示框"——它不是补充说明，是结论本身。 */
.tldr {
  margin: 0 0 24px;
  padding: 12px 16px;
  border-left: 3px solid var(--accent);
  border-radius: 0 8px 8px 0;
  background: var(--accent-soft);
  color: var(--ink);
  font-size: 16px;
  line-height: 1.6;
}
.tldr-label {
  display: inline-block;
  margin-right: 8px;
  font-size: 11px;
  font-weight: 600;
  letter-spacing: .06em;
  text-transform: uppercase;
  color: var(--accent-strong);
  vertical-align: 2px;
  white-space: nowrap;
}
.prose p { margin: 12px 0; }
.prose ul, .prose ol { padding-left: 24px; }
.prose li { margin: 8px 0; }

a { color: var(--accent-text); }
a:hover { color: var(--accent-strong); }

.card {
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: 16px;
  padding: 20px;
  margin: 20px 0;
  box-shadow: var(--shadow-sm);
}
.grid { display: grid; gap: 16px; }
@media (min-width: 720px) { .grid.two { grid-template-columns: 1fr 1fr; } }

/* ---------- playground ---------- */
.toolbar {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
  align-items: center;
  margin: 14px 0;
}
button, .btn {
  font: inherit;
  font-size: 15px;
  border: 1px solid var(--line);
  background: var(--card);
  color: var(--ink);
  border-radius: 999px;
  padding: 8px 24px;
  cursor: pointer;
  transition: border-color 0.15s ease, background-color 0.15s ease, box-shadow 0.15s ease;
}
button:hover { border-color: var(--muted); }
button.primary {
  background: var(--accent);
  border-color: var(--accent-text);
  color: #fff;
  font-weight: 600;
  padding: 8px 28px;
  box-shadow: 0 4px 14px rgba(255, 105, 0, 0.25);
}
button.primary:hover { background: var(--accent-strong); border-color: var(--accent-strong); color: #fff; }
button:disabled { opacity: 0.55; cursor: wait; }
select { font: inherit; font-size: 15px; padding: 8px 12px; border-radius: 999px; border: 1px solid var(--line); background: var(--card); color: var(--ink); }

.editor {
  width: 100%;
  min-height: 320px;
  font-family: ui-monospace, SFMono-Regular, Consolas, "Liberation Mono", Menlo, monospace;
  font-size: 16px;
  line-height: 1.6;
  padding: 14px;
  border: 1px solid var(--line);
  border-radius: 12px;
  background: var(--code-bg);
  color: var(--code-ink);
  resize: vertical;
  tab-size: 4;
  white-space: pre;
  overflow-wrap: normal;
  overflow-x: auto;
}
.editor:focus { outline: 2px solid var(--accent); outline-offset: 1px; }

details.stdin { margin: 12px 0; }
details.stdin summary { cursor: pointer; color: var(--muted); font-size: 14px; }
textarea.stdin-box {
  width: 100%;
  min-height: 64px;
  margin-top: 8px;
  font-family: ui-monospace, SFMono-Regular, Consolas, monospace;
  font-size: 14px;
  padding: 12px;
  border: 1px solid var(--line);
  border-radius: 12px;
  background: var(--card);
  color: var(--ink);
  resize: vertical;
}

.out {
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: 16px;
  padding: 14px;
  min-height: 72px;
  font-family: ui-monospace, SFMono-Regular, Consolas, monospace;
  font-size: 14px;
  white-space: pre-wrap;
  word-break: break-word;
}
.out .meta { color: var(--muted); font-size: 13px; margin-top: 8px; }
.out.ok { border-color: var(--ok); }
.out.err { border-color: var(--err); }
.out.err, .out .err-text { color: var(--err); }

.hint { color: var(--muted); font-size: 13px; margin-top: 8px; }

/* ---------- code blocks & runnable snippets ---------- */
pre.codeblock, .runnable pre {
  background: var(--code-bg);
  color: var(--code-ink);
  border-radius: 16px;
  padding: 16px;
  overflow-x: auto;
  font-size: 13px;
  line-height: 1.6;
  margin: 14px 0;
}
code { font-family: ui-monospace, SFMono-Regular, Consolas, monospace; }
.prose p code, .prose li code, td code, .prose h2 code, .prose h3 code, .card h3 code {
  background: var(--chip-bg);
  color: var(--chip-ink);
  padding: 1px 8px;
  border-radius: 8px;
  font-size: 0.9em;
}
pre.codeblock code, .runnable code { background: none; color: inherit; padding: 0; font-size: inherit; }

.runnable { margin: 20px 0; }
.runnable .run-row { display: flex; align-items: center; gap: 12px; margin-top: -6px; }
.runnable .status { font-size: 13px; color: var(--muted); }
.runnable .run-out {
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: 12px;
  padding: 12px 12px;
  font-size: 14px;
  white-space: pre-wrap;
  word-break: break-word;
  margin: 12px 0 0;
}
.runnable .run-out.ok { border-color: var(--ok); }
.runnable .run-out.err { border-color: var(--err); color: var(--err); }
.runnable textarea.run-in {
  width: 100%;
  min-height: 48px;
  margin: 8px 0 0;
  font-family: ui-monospace, SFMono-Regular, Consolas, monospace;
  font-size: 14px;
  padding: 8px 12px;
  border: 1px solid var(--line);
  border-radius: 12px;
  background: var(--card);
  color: var(--ink);
  resize: vertical;
}

/* ---------- tables ---------- */
table {
  border-collapse: separate;
  border-spacing: 0;
  border: 1px solid var(--line);
  border-radius: 16px;
  overflow: hidden;
  width: 100%;
  margin: 16px 0;
  font-size: 14px;
  background: var(--card);
}
th, td {
  border: none;
  border-bottom: 1px solid var(--line);
  padding: 8px 14px;
  text-align: left;
  vertical-align: top;
}
tr:last-child td, tr:last-child th { border-bottom: none; }
th { background: var(--chip-bg); font-size: 13px; letter-spacing: 0.01em; }
tr { transition: background-color 0.12s ease; }
tr:hover td { background: rgba(255, 105, 0, 0.045); }

/* ---------- misc ---------- */
/* 广告位容器：只负责上下间距。
   不要给它边框 / 背景 / 内边距 —— 它包着的是真实广告，虚线框会把广告围起来；
   而广告尚未填充时（AdSense 审核期不投放），一个空虚线盒子比"什么都没有"
   更像页面坏了。宁可什么都不显示。 */
.ad-slot { margin: 28px 0; }
.ad-slot:empty { display: none; }
footer.site { text-align: center; border-top: 1px solid var(--line); padding: 24px 0 44px; color: var(--muted); font-size: 14px; background: var(--card); }
footer.site .wrap { display: flex; flex-wrap: wrap; gap: 14px; justify-content: center; }
footer.site a { color: var(--muted); }
footer.site::before {
  content: "Everything runs in your browser — no account, no tracking.";
  display: block;
  color: var(--muted);
  font-size: 13px;
  margin-bottom: 8px;
}
:root[lang|="es"] footer.site::before { content: "Todo se ejecuta en tu navegador — sin cuenta, sin rastreo."; }
:root[lang|="zh"] footer.site::before { content: "全部功能在你的浏览器里运行 — 无账号、无追踪。"; }

.badge {
  display: inline-block;
  background: var(--accent-soft);
  color: var(--accent-text);
  font-size: 12px;
  font-weight: 600;
  border-radius: 999px;
  padding: 2px 12px;
}
.badge.b-easy { background: #e5f6ec; color: #177a4c; }
.badge.b-mid { background: #fff3d6; color: #9a6b00; }
.badge.b-hard { background: #ffe6df; color: #c2410c; }
:root[data-theme="dark"] .badge.b-easy { background: rgba(76, 195, 138, 0.15); color: #4cc38a; }
:root[data-theme="dark"] .badge.b-mid { background: rgba(255, 171, 64, 0.15); color: #ffab40; }
:root[data-theme="dark"] .badge.b-hard { background: rgba(255, 107, 97, 0.15); color: #ff6b61; }

/* ---------- hero (homepage) — Xiaomi style: centered, big, airy ---------- */
.hero {
  text-align: center;
  padding: 38px 16px 32px;
  margin: 0 0 24px;
  border-bottom: 1px solid var(--line);
}
.hero h1 { font-size: 34px; margin: 0 0 12px; font-weight: 800; }
.hero .tagline { font-size: 18px; margin-bottom: 16px; }
.hero-chips { display: flex; flex-wrap: wrap; gap: 12px; margin: 0; justify-content: center; }
.chip {
  background: var(--card);
  border: 1px solid var(--line);
  color: var(--muted);
  font-size: 13px;
  border-radius: 999px;
  padding: 4px 16px;
  box-shadow: var(--shadow-sm);
}

/* ---------- theme toggle ---------- */
.theme-toggle {
  margin-left: auto;
  border: 1px solid var(--line);
  background: var(--card);
  font-size: 14px;
  line-height: 1;
  padding: 8px 12px;
  border-radius: 999px;
}
.theme-toggle:hover { border-color: var(--accent-text); }

/* ---------- syntax tokens ---------- */
.tok-c { color: var(--tok-c); font-style: italic; }
.tok-k { color: var(--tok-k); }
.tok-s { color: var(--tok-s); }
.tok-n { color: var(--tok-n); }
.tok-p { color: var(--tok-p); }
.tok-sd { color: var(--tok-sd); }

/* ---------- copy button on code blocks ---------- */
pre { position: relative; }
.copy-btn {
  position: absolute;
  top: 10px;
  right: 10px;
  font-size: 12px;
  padding: 3px 12px;
  border-radius: 999px;
  border: 1px solid rgba(232, 232, 237, 0.18);
  background: rgba(60, 60, 68, 0.55);
  color: #e8e8ed;
  opacity: 0.5;
  transition: opacity 0.15s ease;
}
pre:hover .copy-btn, .copy-btn:focus-visible { opacity: 1; }
.copy-btn.done { color: #4cc38a; border-color: rgba(76, 195, 138, 0.5); }

/* ---------- editor scrollbars ---------- */
.editor::-webkit-scrollbar, pre::-webkit-scrollbar { height: 10px; width: 10px; }
.editor::-webkit-scrollbar-thumb, pre::-webkit-scrollbar-thumb {
  background: #3a3a40;
  border-radius: 8px;
}
.editor::-webkit-scrollbar-track, pre::-webkit-scrollbar-track { background: transparent; }

/* ---------- terminal-window chrome around editors ---------- */
.term {
  background: var(--code-bg);
  border: 1px solid var(--line);
  border-radius: 16px;
  overflow: hidden;
  margin: 14px 0;
  box-shadow: var(--shadow-sm);
}
.term-bar {
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 8px 14px;
  background: #1a1a1f;
  border-bottom: 1px solid #26262c;
}
.dot { width: 10px; height: 10px; border-radius: 50%; opacity: 0.9; }
.dot.r { background: #ff5f57; }
.dot.y { background: #febc2e; }
.dot.g { background: #28c840; }
.term-title {
  margin-left: 8px;
  font-family: ui-monospace, SFMono-Regular, Consolas, monospace;
  font-size: 12px;
  color: #86868b;
  user-select: none;
}
.term .editor {
  border: none;
  border-radius: 0;
  display: block;
  min-height: 280px;
}
.term .editor:focus { outline: none; }
.term:focus-within { outline: 2px solid var(--accent); outline-offset: 1px; }

/* ---------- practice judge ---------- */
.judge-panel { margin: 24px 0; }
.judge-actions { display: flex; flex-wrap: wrap; gap: 12px; align-items: center; margin: 12px 0; }
#results { margin-top: 14px; }
.summary { font-weight: 600; padding: 12px 16px; border-radius: 16px; margin-bottom: 12px; font-size: 15px; }
.summary.accepted { background: #e5f6ec; color: #177a4c; border: 1px solid #bfe8d2; }
.summary.failed { background: #ffe9e6; color: #a13327; border: 1px solid #ffcfc7; }
.summary.running { background: var(--accent-soft); color: var(--accent-text); }
:root[data-theme="dark"] .summary.accepted { background: rgba(76, 195, 138, 0.12); color: #4cc38a; border-color: rgba(76, 195, 138, 0.35); }
:root[data-theme="dark"] .summary.failed { background: rgba(255, 107, 97, 0.12); color: #ff6b61; border-color: rgba(255, 107, 97, 0.35); }
.summary a { color: inherit; text-decoration: underline; font-weight: 700; }
.summary.running { position: relative; overflow: hidden; }
.summary.running::after {
  content: "";
  position: absolute;
  left: 0;
  bottom: 0;
  height: 3px;
  width: 100%;
  background: linear-gradient(90deg, transparent, var(--accent), transparent);
  animation: sweep 1.1s linear infinite;
}
@keyframes sweep { from { transform: translateX(-100%); } to { transform: translateX(100%); } }
.test-result { border: 1px solid var(--line); border-radius: 16px; padding: 12px 16px; margin: 8px 0; background: var(--card); animation: fadeUp 0.25s ease both; }
.test-result .t-head { font-weight: 600; font-size: 14px; }
.test-result.pass .t-head { color: var(--ok); }
.test-result.fail .t-head { color: var(--err); }
.t-io { display: grid; gap: 8px; margin-top: 8px; }
@media (min-width: 720px) { .t-io.three { grid-template-columns: 1fr 1fr 1fr; } }
.t-io .io-box pre {
  background: var(--code-bg); color: var(--code-ink);
  border-radius: 12px; padding: 8px 12px; font-size: 13px;
  white-space: pre-wrap; word-break: break-word; margin: 4px 0 0;
}
.t-io .io-box .io-label { font-size: 12px; color: var(--muted); font-weight: 600; text-transform: uppercase; letter-spacing: 0.04em; }
.t-io .io-box pre.bad { outline: 2px solid var(--err); outline-offset: -2px; }
.t-io .io-box pre.good { outline: 2px solid var(--ok); outline-offset: -2px; }
@keyframes popIn { from { transform: scale(0.97); opacity: 0; } to { transform: scale(1); opacity: 1; } }
.summary.accepted { animation: popIn 0.2s ease; }
#reset-code:hover { border-color: var(--err); color: var(--err); }

/* ---------- cards: Xiaomi hover lift ---------- */
.grid .card, .feature {
  transition: transform 0.18s ease, box-shadow 0.18s ease, border-color 0.18s ease;
}
.grid .card:hover, .feature:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-md);
  border-color: var(--line);
}

/* ---------- homepage feature cards ---------- */
.features { display: grid; gap: 16px; margin: 24px 0 12px; }
@media (min-width: 720px) { .features { grid-template-columns: 1fr 1fr 1fr; } }
.feature {
  display: block;
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: 16px;
  padding: 20px 20px;
  text-decoration: none;
  color: var(--ink);
  box-shadow: var(--shadow-sm);
}
.feature:hover { border-color: var(--line); color: var(--ink); }
.feature h3 { margin: 0 0 8px; font-size: 16px; font-weight: 700; }
.feature:hover h3 { color: var(--accent-text); }
.feature p { margin: 0; color: var(--muted); font-size: 14px; line-height: 1.6; }

/* ---------- language dropdown (native <details>: no JS, closes on outside click) ---------- */
.lang-menu {
  position: relative;
  margin-left: auto;
}
.lang-menu-trigger {
  list-style: none;
  cursor: pointer;
  border: 1px solid var(--line);
  background: var(--card);
  color: var(--muted);
  font-size: 14px;
  padding: 8px 14px;
  border-radius: 999px;
  user-select: none;
  transition: border-color 0.15s ease, color 0.15s ease;
  white-space: nowrap;
}
.lang-menu-trigger::-webkit-details-marker { display: none; }
.lang-menu-trigger:hover { border-color: var(--accent-text); color: var(--accent-text); }
.lang-menu[open] .lang-menu-trigger { border-color: var(--accent-text); color: var(--accent-text); }
.lang-menu-trigger .caret {
  display: inline-block;
  font-size: 11px;
  margin-left: 3px;
  transition: transform 0.15s ease;
}
.lang-menu[open] .lang-menu-trigger .caret { transform: rotate(180deg); }

.lang-menu-list {
  position: absolute;
  right: 0;
  top: calc(100% + 8px);
  min-width: 150px;
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: 16px;
  box-shadow: var(--shadow-md);
  padding: 8px;
  z-index: 30;
  animation: fadeUp 0.15s ease both;
}
.lang-menu-item {
  display: block;
  padding: 8px 14px;
  border-radius: 8px;
  color: var(--ink);
  text-decoration: none;
  font-size: 14px;
  white-space: nowrap;
}
.lang-menu-item:hover { background: var(--chip-bg); color: var(--ink); }
.lang-menu-item.is-current { color: var(--accent-text); font-weight: 700; }
.lang-menu-item.is-current::after { content: " ✓"; }

/* ---------- motion preferences ---------- */
@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after { transition: none !important; animation: none !important; }
  html { scroll-behavior: auto; }
}

/* ============================================================
   第五轮:深度解析 / 经验值 / 成就徽章 / 通关知识卡
   ============================================================ */

/* ---------- 深度解析(题库页) ---------- */
.deep { margin: 32px 0 8px; }
.deep > h2 { margin-bottom: 12px; }
.deep-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 12px;
}
.deep-cell {
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: 16px;
  padding: 16px 16px;
  box-shadow: var(--shadow-sm);
  transition: transform 0.18s ease, box-shadow 0.18s ease;
}
.deep-cell:hover { transform: translateY(-2px); box-shadow: var(--shadow-md); }
.deep-cell h3 {
  margin: 0 0 8px;
  font-size: 12px;
  font-weight: 700;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--accent-text);
}
.deep-cell p, .deep-cell li {
  margin: 0;
  font-size: 14px;
  line-height: 1.75;
  color: var(--ink);
}
.deep-cell ul { margin: 0; padding-left: 20px; }
.deep-cell li + li { margin-top: 8px; }
.deep-cell code {
  font-size: 0.9em;
  padding: 1px 4px;
  border-radius: 8px;
  background: var(--chip-bg);
  color: var(--ink);
}
.deep-wide { grid-column: 1 / -1; }
.deep-takeaway {
  margin-top: 12px;
  padding: 16px 20px;
  border-radius: 16px;
  border: 1px dashed var(--line);
  border: 1px dashed color-mix(in srgb, var(--accent) 45%, var(--line));
  background: var(--accent-soft);
}
.deep-takeaway h3 {
  margin: 0 0 8px;
  font-size: 12px;
  font-weight: 700;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--accent-text);
}
.deep-takeaway ul { margin: 0; padding-left: 20px; }
.deep-takeaway li { font-size: 14px; line-height: 1.75; }
.deep-takeaway li + li { margin-top: 8px; }
@media (max-width: 720px) {
  .deep-grid { grid-template-columns: 1fr; }
}

/* ---------- 经验值 / 等级 ---------- */
.xp-panel {
  display: flex;
  align-items: center;
  gap: 14px;
  margin: 0 0 14px;
  padding: 14px 16px;
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: 16px;
  box-shadow: var(--shadow-sm);
}
.lvl-badge {
  position: relative;
  flex: 0 0 auto;
  width: 46px;
  height: 46px;
  display: grid;
  place-items: center;
  font-weight: 800;
  font-size: 15px;
  color: #fff;
  font-variant-numeric: tabular-nums;
}
.lvl-badge svg { position: absolute; inset: 0; width: 100%; height: 100%; }
.lvl-badge span { position: relative; z-index: 1; }
.xp-body { flex: 1 1 auto; min-width: 0; }
.xp-head {
  display: flex;
  justify-content: space-between;
  align-items: baseline;
  gap: 12px;
  font-size: 13px;
  margin-bottom: 8px;
}
.xp-head strong { font-size: 14px; }
.xp-head .xp-num { color: var(--muted); font-variant-numeric: tabular-nums; white-space: nowrap; }
.xp-bar {
  height: 9px;
  border-radius: 999px;
  background: var(--chip-bg);
  overflow: hidden;
}
.xp-fill {
  height: 100%;
  border-radius: 999px;
  background: linear-gradient(90deg, var(--accent) 0%, #ffa257 100%);
  transition: width 0.7s cubic-bezier(0.2, 0.8, 0.2, 1);
  position: relative;
  overflow: hidden;
}
.xp-fill::after {
  content: "";
  position: absolute;
  inset: 0;
  background: linear-gradient(90deg, transparent, rgba(255, 255, 255, 0.5), transparent);
  transform: translateX(-100%);
  animation: xp-shine 2.6s ease-in-out infinite;
}
@keyframes xp-shine {
  0%, 55% { transform: translateX(-100%); }
  100% { transform: translateX(100%); }
}
.xp-streak {
  flex: 0 0 auto;
  text-align: center;
  font-size: 12px;
  color: var(--muted);
  line-height: 1.25;
}
.xp-streak b { display: block; font-size: 17px; color: var(--ink); }

/* ---------- 错误示例(亲手踩一次) ---------- */
.deep-demo {
  margin-top: 12px;
  background: var(--card);
  border: 1px solid var(--line);
  border-left: 3px solid var(--err);
  border-radius: 16px;
  box-shadow: var(--shadow-sm);
  overflow: hidden;
}
.deep-demo > summary {
  cursor: pointer;
  padding: 12px 16px;
  font-size: 14px;
  font-weight: 600;
  color: var(--ink);
  list-style: none;
  display: flex;
  align-items: center;
  gap: 8px;
  transition: background 0.15s ease;
}
.deep-demo > summary::-webkit-details-marker { display: none; }
.deep-demo > summary:hover { background: var(--chip-bg); }
.deep-demo > summary::after {
  content: "▾";
  margin-left: auto;
  color: var(--muted);
  font-size: 12px;
  transition: transform 0.2s ease;
}
.deep-demo[open] > summary::after { transform: rotate(180deg); }
.deep-demo-label {
  margin: 0 16px 12px;
  font-size: 13px;
  line-height: 1.65;
  color: var(--muted);
}
.deep-demo-label code {
  padding: 1px 4px;
  border-radius: 8px;
  background: var(--chip-bg);
  color: var(--ink);
  font-size: 0.92em;
}
.deep-demo > pre.bad-code {
  position: relative;
  margin: 0 16px;
  padding: 14px 16px;
  border-radius: 12px;
  background: var(--code-bg);
  color: var(--code-ink);
  overflow: auto;
  font-size: 13px;
  line-height: 1.6;
}
.deep-demo > pre.bad-code code { font-family: inherit; }
.try-bad {
  margin: 12px 16px 16px;
  padding: 8px 16px;
  border-radius: 999px;
  border: 1px solid var(--accent);
  background: var(--accent-soft);
  color: var(--accent-text);
  font: inherit;
  font-size: 13px;
  font-weight: 700;
  cursor: pointer;
  transition: background 0.15s ease, color 0.15s ease, transform 0.15s ease;
}
.try-bad:hover { background: var(--accent); color: #fff; transform: translateY(-1px); }
.try-bad:active { transform: none; }

/* ---------- 闯关链胶囊(三态,暗色自适应) ---------- */
.j-pill {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 8px 12px;
  border-radius: 999px;
  font-size: 13px;
  text-decoration: none;
  border: 1px solid var(--line);
  background: var(--card);
  color: var(--muted);
  transition: transform 0.16s ease, border-color 0.16s ease;
}
.j-pill:hover { transform: translateY(-1px); border-color: var(--accent-text); }
.j-pill.is-done {
  background: var(--card);
  background: color-mix(in srgb, var(--ok) 12%, var(--card));
  border-color: var(--line);
  border-color: color-mix(in srgb, var(--ok) 38%, var(--line));
  color: var(--ok);
}
:root[data-theme="dark"] .j-pill.is-done {
  background: var(--card);
  background: color-mix(in srgb, var(--ok) 18%, var(--card));
}
.j-pill.is-current {
  background: var(--accent-soft);
  border-color: var(--accent-text);
  color: var(--accent-text);
  font-weight: 700;
}

/* ---------- 成就徽章(六边形底座,替代裸 emoji) ---------- */
.ach-card { text-align: center; padding: 16px 12px 14px; }
.ach-ico {
  width: 48px;
  height: 48px;
  margin: 0 auto 8px;
  display: grid;
  place-items: center;
  font-size: 21px;
  line-height: 1;
  background: linear-gradient(160deg, #ffb27a 0%, var(--accent) 100%);
  clip-path: polygon(50% 0%, 93% 25%, 93% 75%, 50% 100%, 7% 75%, 7% 25%);
  box-shadow: 0 4px 12px rgba(255, 105, 0, 0.28);
}
.ach-card.is-locked .ach-ico {
  background: linear-gradient(160deg, #d5d5db 0%, #b4b4bc 100%);
  box-shadow: none;
  filter: grayscale(1);
  opacity: 0.75;
}
:root[data-theme="dark"] .ach-card.is-locked .ach-ico {
  background: linear-gradient(160deg, #3d3d44 0%, #2a2a30 100%);
}
.ach-card.is-locked .ach-name { color: var(--muted); }

/* ---------- 通关知识卡 / 成就 toast ---------- */
.toast-stack {
  position: fixed;
  right: 18px;
  bottom: 18px;
  z-index: 90;
  display: flex;
  flex-direction: column;
  gap: 12px;
  max-width: min(360px, calc(100vw - 36px));
  pointer-events: none;
}
.toast {
  pointer-events: auto;
  background: var(--card);
  border: 1px solid var(--line);
  border-left: 3px solid var(--accent);
  border-radius: 16px;
  padding: 12px 14px;
  box-shadow: var(--shadow-md);
  font-size: 14px;
  line-height: 1.55;
  animation: toast-in 0.42s cubic-bezier(0.2, 0.9, 0.2, 1);
}
.toast.is-out { animation: toast-out 0.3s ease forwards; }
@keyframes toast-in {
  from { opacity: 0; transform: translateY(14px) scale(0.97); }
  to { opacity: 1; transform: none; }
}
@keyframes toast-out {
  to { opacity: 0; transform: translateY(8px) scale(0.98); }
}
.toast .toast-head {
  display: flex;
  align-items: center;
  gap: 8px;
  font-weight: 700;
  margin-bottom: 4px;
}
.toast .toast-xp {
  font-variant-numeric: tabular-nums;
  color: var(--accent-text);
  font-weight: 800;
}
.toast.know { border-left-color: var(--ok); }
.toast ul { margin: 8px 0 0; padding-left: 20px; color: var(--muted); }
.toast li + li { margin-top: 4px; }

@media (max-width: 560px) {
  .toast-stack { right: 10px; left: 10px; bottom: 10px; max-width: none; }
  .xp-panel { gap: 12px; padding: 12px; }
  .xp-streak { display: none; }
}

/* ---------- 题库目录:按主题筛选(build-topics.js 生成的过滤条) ---------- */
.topic-filter {
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: 16px;
  padding: 14px 16px;
  margin: 20px 0 24px;
  box-shadow: var(--shadow-sm);
}
.topic-chips {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}
.topic-chip {
  font: inherit;
  font-size: 13px;
  line-height: 1.2;
  padding: 8px 12px;
  border-radius: 999px;
  border: 1px solid var(--line);
  background: var(--chip-bg);
  color: var(--chip-ink);
  cursor: pointer;
  transition: background-color 0.15s ease, border-color 0.15s ease, color 0.15s ease;
}
.topic-chip:hover { border-color: var(--accent-text); color: var(--accent-text); }
.topic-chip.is-on {
  background: var(--accent);
  border-color: var(--accent-text);
  color: #fff;
}
.topic-chip:focus-visible,
.topic-search:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 2px;
}
.topic-tools {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 12px;
  margin-top: 12px;
}
.topic-search {
  font: inherit;
  font-size: 14px;
  flex: 1 1 220px;
  min-width: 0;
  padding: 8px 12px;
  border-radius: 12px;
  border: 1px solid var(--line);
  background: var(--bg);
  color: var(--ink);
}
.topic-search::placeholder { color: var(--muted); }
.topic-count {
  font-size: 13px;
  color: var(--muted);
  font-variant-numeric: tabular-nums;
  white-space: nowrap;
}
.topic-empty {
  margin: 12px 0 0;
  font-size: 14px;
  color: var(--muted);
}
@media (max-width: 560px) {
  .topic-filter { padding: 12px; border-radius: 12px; }
  .topic-chip { font-size: 12px; padding: 4px 12px; }
  .topic-search { flex: 1 1 100%; }
}

/* ---------- course path (lessons) ---------- */
.course-path {
  margin: 24px 0 32px;
  padding: 16px 20px;
  border: 1px solid var(--line);
  border-radius: 16px;
  background: var(--card);
  box-shadow: var(--shadow-sm);
}
.course-path-title {
  margin: 0 0 12px;
  font-size: 12px;
  font-weight: 600;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--muted);
}
.course-path ol {
  display: flex;
  flex-wrap: wrap;
  gap: 8px 8px;
  margin: 0;
  padding: 0;
  list-style: none;
}
.course-path li {
  margin: 0;
  font-size: 13px;
}
.course-path li a,
.course-path li strong {
  display: inline-block;
  padding: 4px 12px;
  border-radius: 999px;
  border: 1px solid var(--line);
  background: var(--bg);
  color: var(--ink);
  text-decoration: none;
  font-weight: 500;
}
.course-path li a:hover {
  border-color: var(--accent-text);
  color: var(--accent-text);
  background: var(--accent-soft);
}
.course-path li.is-current strong {
  border-color: var(--accent-text);
  background: var(--accent-soft);
  color: var(--accent-strong);
  font-weight: 700;
}
.course-path-links {
  margin: 12px 0 0;
  font-size: 13px;
  color: var(--muted);
}
.course-path-links a { color: var(--accent-strong); }

/* ---------- practice box ---------- */
.practice-box {
  margin: 32px 0 8px;
  padding: 20px 20px;
  border: 1px solid var(--line);
  border-left: 3px solid var(--accent);
  border-radius: 12px;
  background: var(--card);
}
.practice-box h2 {
  margin: 0 0 8px;
  font-size: 17px;
}
.practice-box p {
  margin: 0 0 12px;
  font-size: 14px;
  color: var(--muted);
}
.practice-box ul {
  margin: 0;
  padding-left: 20px;
}
.practice-box li { margin: 4px 0; }

/* ---------- lesson index ---------- */
.lesson-grid { display: grid; gap: 14px; margin: 24px 0; }
.lesson-card {
  display: block;
  padding: 16px 20px;
  border: 1px solid var(--line);
  border-radius: 16px;
  background: var(--card);
  box-shadow: var(--shadow-sm);
  text-decoration: none;
  color: inherit;
  transition: transform 0.16s ease, box-shadow 0.16s ease, border-color 0.16s ease;
}
.lesson-card:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-md);
  border-color: var(--accent-text);
}
.lesson-card .num {
  display: inline-block;
  min-width: 22px;
  font-size: 12px;
  font-weight: 700;
  color: var(--accent-strong);
}
.lesson-card h3 { margin: 0 0 4px; font-size: 16px; }
.lesson-card p { margin: 0; font-size: 14px; color: var(--muted); }

/* ==========================================================================
   Round 20 — visual polish
   Layered depth, a real brand mark, warmer surfaces, calmer tables.
   All values come from the token scale above; nothing here hardcodes a colour
   except the accent tints, which are declared once per theme.
   ========================================================================== */

/* --- brand mark: replace the plain "</>" chip with a rounded badge --- */
.brand::before {
  content: "</>";
  font-family: ui-monospace, SFMono-Regular, Consolas, monospace;
  font-weight: 700;
  font-size: 11px;
  letter-spacing: -0.02em;
  background: var(--accent);
  color: #fff;
  border-radius: 8px;
  padding: 4px 8px;
  margin-right: 8px;
  display: inline-block;
  line-height: 1.35;
  box-shadow: 0 1px 3px rgba(238, 95, 0, 0.35);
  vertical-align: 1px;
}

/* --- cards: two-layer depth, lift on hover only where it is interactive --- */
.card {
  border-radius: 16px;
  padding: 20px;
  margin: 20px 0;
  transition: border-color 0.18s ease, box-shadow 0.18s ease;
}
.card:hover { border-color: var(--line); }
.card:hover { border-color: color-mix(in srgb, var(--accent) 22%, var(--line)); }

.feature {
  padding: 20px;
  border-radius: 16px;
  transition: transform 0.18s cubic-bezier(0.2, 0.7, 0.3, 1),
              box-shadow 0.18s ease,
              border-color 0.18s ease;
}
.feature:hover {
  transform: translateY(-3px);
  box-shadow: var(--shadow-md);
  border-color: var(--accent);
  border-color: color-mix(in srgb, var(--accent) 30%, var(--line));
}
@media (prefers-reduced-motion: reduce) {
  .feature { transition: none; }
  .feature:hover { transform: none; }
}

/* --- section headings get a quiet accent tick so long pages have landmarks --- */
.prose > h2 {
  display: flex;
  align-items: baseline;
  gap: 10px;
  padding-bottom: 8px;
  border-bottom: 1px solid var(--line);
}
.prose > h2::before {
  content: "";
  flex: 0 0 auto;
  width: 3px;
  height: 0.82em;
  border-radius: 2px;
  background: var(--accent);
  transform: translateY(-1px);
}

/* --- tables: zebra + softer rules, so 20-row problem lists stay scannable --- */
table { border-collapse: separate; border-spacing: 0; }
table th {
  background: var(--chip-bg);
  font-weight: 600;
  font-size: 13px;
  letter-spacing: 0.01em;
  text-transform: none;
  color: var(--chip-ink);
  border-bottom: 1px solid var(--line);
}
table th:first-child { border-top-left-radius: 10px; }
table th:last-child { border-top-right-radius: 10px; }
table tbody tr:nth-child(even) { background: transparent; }
table tbody tr:nth-child(even) { background: color-mix(in srgb, var(--chip-bg) 45%, transparent); }
table tbody tr:hover { background: var(--accent-soft); }
table td { border-bottom: 1px solid var(--line); }
table tr:last-child td { border-bottom: 0; }

/* --- code blocks: one consistent shell, subtle top highlight --- */
pre.codeblock,
.runnable pre,
.term {
  border-radius: 12px;
}
pre.codeblock {
  box-shadow: inset 0 1px 0 rgba(255, 255, 255, 0.06), var(--shadow-sm);
}
.runnable {
  border: 1px solid var(--line);
  border-radius: 16px;
  padding: 16px 16px 12px;
  background: var(--card);
  box-shadow: var(--shadow-sm);
}
.runnable pre { margin: 0; }
.runnable .run-row { margin-top: 12px; }

/* --- buttons: unify the pill treatment across the site --- */
.run-btn,
.try-bad,
.copy-btn,
.topic-chip,
.lang-menu-trigger,
.theme-toggle {
  transition: background-color 0.16s ease, border-color 0.16s ease,
              color 0.16s ease, transform 0.16s ease, box-shadow 0.16s ease;
}
.run-btn:active,
.try-bad:active { transform: translateY(1px); }

/* --- badges: slightly tighter, more like labels than chips --- */
.badge {
  border-radius: 999px;
  padding: 3px 10px;
  font-size: 12px;
  font-weight: 600;
  letter-spacing: 0.01em;
}

/* --- tldr block: make the "answer first" block feel deliberate --- */
.tldr {
  border-left-width: 3px;
  border-radius: 0 12px 12px 0;
  padding: 12px 16px;
}
.tldr strong { color: var(--ink); }

/* --- course path pills: match card radius and hover --- */
.course-path { border-radius: 16px; padding: 16px 20px; }
.course-path li a,
.course-path li strong { border-radius: 999px; padding: 5px 12px; }

/* --- practice box: align with the card language --- */
.practice-box { border-radius: 16px; padding: 20px; }

/* --- lesson cards --- */
.lesson-card { border-radius: 16px; padding: 16px 20px; }

/* --- footer: calmer, more legible --- */
footer.site { font-size: 13px; }

/* --- dark-mode specific corrections for the new surfaces --- */
:root[data-theme="dark"] table tbody tr:nth-child(even) {
  background: transparent;
  background: color-mix(in srgb, var(--chip-bg) 60%, transparent);
}
:root[data-theme="dark"] table tbody tr:hover { background: var(--accent-soft); }
:root[data-theme="dark"] .brand::before { box-shadow: 0 1px 3px rgba(0, 0, 0, 0.5); }
:root[data-theme="dark"] .runnable { box-shadow: none; }
:root[data-theme="dark"] pre.codeblock {
  box-shadow: inset 0 1px 0 rgba(255, 255, 255, 0.04);
}

/* --- mobile: tighter vertical rhythm, no horizontal surprises --- */
@media (max-width: 640px) {
  .prose > h2 { margin-top: 32px; }
  .card, .feature, .runnable, .practice-box { padding: 16px; }
  .course-path { padding: 12px 16px; }
  table th, table td { padding: 8px 10px; }
}