/* ---------- Tokens ---------- */
:root {
  --font: Bahnschrift, "DIN Alternate", "Segoe UI", system-ui, -apple-system, "Microsoft YaHei", "PingFang SC", "Noto Sans SC", sans-serif;
  --mono: "Cascadia Code", Consolas, "SFMono-Regular", Menlo, monospace;

  --bg: #f6f7f9;
  --surface: #ffffff;
  --surface-2: #eef1f5;
  --text: #1b2230;
  --muted: #5d6778;
  --border: #dde2ea;
  --brand: #2f6fdf;
  --good: #1e8a4c;
  --good-bg: #e3f5ea;
  --bad: #c2362f;
  --bad-bg: #fbe6e4;
  --warn: #a05a00;
  --warn-bg: #fff1dc;
  --shadow: 0 1px 2px rgb(20 30 50 / 6%), 0 4px 16px rgb(20 30 50 / 6%);

  --cp: #8a46c9;

  --code-bg: #f1f3f7;
  --hl-keyword: #a6266e;
  --hl-string: #1c7a3d;
  --hl-number: #b35900;
  --hl-comment: #7a8394;
  --hl-title: #2458c4;
  --hl-type: #7c3aad;

  --accent: var(--cp);
  --radius: 14px;
  color-scheme: light;
}

@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --bg: #11151c;
    --surface: #1a2029;
    --surface-2: #232b37;
    --text: #e6eaf1;
    --muted: #9aa5b8;
    --border: #2e3746;
    --brand: #6b9cff;
    --good: #52c783;
    --good-bg: #173226;
    --bad: #ff7b72;
    --bad-bg: #3a1d1d;
    --warn: #f0b35a;
    --warn-bg: #3a2c14;
    --shadow: 0 1px 2px rgb(0 0 0 / 30%), 0 6px 20px rgb(0 0 0 / 25%);
    --cp: #c08cf2;
    --code-bg: #141920;
    --hl-keyword: #ff7ab8;
    --hl-string: #7fd69b;
    --hl-number: #f0b35a;
    --hl-comment: #7b8698;
    --hl-title: #8fb4ff;
    --hl-type: #d0a4ff;
    color-scheme: dark;
  }
}
:root[data-theme="dark"] {
  --bg: #11151c;
  --surface: #1a2029;
  --surface-2: #232b37;
  --text: #e6eaf1;
  --muted: #9aa5b8;
  --border: #2e3746;
  --brand: #6b9cff;
  --good: #52c783;
  --good-bg: #173226;
  --bad: #ff7b72;
  --bad-bg: #3a1d1d;
  --warn: #f0b35a;
  --warn-bg: #3a2c14;
  --shadow: 0 1px 2px rgb(0 0 0 / 30%), 0 6px 20px rgb(0 0 0 / 25%);
  --cp: #c08cf2;
  --code-bg: #141920;
  --hl-keyword: #ff7ab8;
  --hl-string: #7fd69b;
  --hl-number: #f0b35a;
  --hl-comment: #7b8698;
  --hl-title: #8fb4ff;
  --hl-type: #d0a4ff;
  color-scheme: dark;
}


/* ---------- Base ---------- */
* { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; }
body {
  margin: 0;
  font-family: var(--font);
  font-size: 17px;
  line-height: 1.6;
  background: var(--bg);
  color: var(--text);
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}
a { color: var(--accent); }
code, pre, kbd { font-family: var(--mono); font-size: 0.9em; }
h1, h2, h3 { line-height: 1.25; letter-spacing: -0.01em; }
button { font: inherit; color: inherit; }
:focus-visible { outline: 3px solid var(--accent); outline-offset: 2px; }

.skip { position: absolute; left: -999px; }
.skip:focus { left: 16px; top: 8px; z-index: 10; background: var(--surface); padding: 6px 10px; border-radius: 8px; }

.zh { color: var(--muted); }
.zh-line { display: block; font-size: 0.92em; margin-top: 2px; }

/* ---------- Header ---------- */
.site-header {
  position: sticky; top: env(safe-area-inset-top, 0px); z-index: 5;
  background: color-mix(in srgb, var(--bg) 85%, transparent);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--border);
}
.header-inner {
  max-width: 1040px; margin: 0 auto; padding: 10px 16px;
  display: flex; align-items: center; gap: 12px;
}
.brand {
  display: flex; align-items: center; gap: 8px;
  font-weight: 700; font-size: 1.1rem; color: var(--text); text-decoration: none; white-space: nowrap;
}
.brand-mark {
  display: grid; place-items: center; min-width: 28px; height: 28px; padding: 0 5px; border-radius: 8px;
  background: var(--cp); color: #fff; font-size: 0.8rem;
}
.header-actions { display: flex; gap: 6px; margin-left: auto; }
.icon-btn {
  display: grid; place-items: center; width: 38px; height: 38px; border-radius: 10px;
  border: 1px solid var(--border); background: var(--surface); cursor: pointer; font-weight: 700;
}

/* ---------- Layout ---------- */
main { flex: 1; width: 100%; max-width: 1040px; margin: 0 auto; padding: 24px 16px 48px; }
main:focus { outline: none; }
.narrow { max-width: 760px; margin: 0 auto; }
.site-footer { text-align: center; color: var(--muted); font-size: 0.85rem; padding: 20px 16px 28px; }
.muted { color: var(--muted); }
.loading { color: var(--muted); }

.crumbs { font-size: 0.9rem; color: var(--muted); margin-bottom: 12px; display: flex; flex-wrap: wrap; gap: 6px; }
.crumbs a { color: var(--muted); }
.crumbs span[aria-hidden] { opacity: 0.6; }

.eyebrow { text-transform: uppercase; letter-spacing: 0.12em; font-size: 0.78rem; color: var(--accent); font-weight: 700; margin: 0 0 6px; }
.hero { padding: 12px 0 20px; }
.hero h1 { font-size: clamp(1.8rem, 5vw, 2.6rem); margin: 0 0 8px; }
.lede { color: var(--muted); max-width: 60ch; margin: 0; }

/* ---------- Buttons & pills ---------- */
.btn {
  display: inline-flex; align-items: center; justify-content: center; gap: 8px;
  padding: 10px 16px; border-radius: 10px; border: 1px solid var(--border);
  background: var(--surface); color: var(--text); text-decoration: none; cursor: pointer; font-weight: 600;
  min-height: 44px;
}
.btn:hover { border-color: var(--accent); }
.btn.primary { background: var(--accent); border-color: var(--accent); color: #fff; }
:root[data-theme="dark"] .btn.primary { color: #0d1117; }
@media (prefers-color-scheme: dark) { :root:not([data-theme="light"]) .btn.primary { color: #0d1117; } }
.btn-row { display: flex; flex-wrap: wrap; gap: 10px; }
.pill {
  display: inline-block; padding: 4px 10px; border-radius: 999px; font-size: 0.85rem; font-weight: 600;
  background: var(--surface-2); color: var(--muted); text-decoration: none;
}
.pill.warn { background: var(--warn-bg); color: var(--warn); }

/* ---------- Projects ---------- */
.project-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(min(100%, 300px), 1fr)); gap: 16px; }
.project-card {
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 18px; box-shadow: var(--shadow); display: flex; flex-direction: column; gap: 12px;
}
.project-link { display: flex; flex-direction: column; gap: 4px; text-decoration: none; color: var(--text); }
.project-link:hover h2 { color: var(--accent); }
.pid {
  align-self: flex-start; font-family: var(--mono); font-size: 0.85rem; font-weight: 700;
  color: var(--accent); background: color-mix(in srgb, var(--accent) 12%, transparent);
  padding: 2px 8px; border-radius: 6px; font-variant-numeric: tabular-nums;
}
.project-link h2 { margin: 0; font-size: 1.25rem; text-wrap: balance; }
.summary { margin: 0; color: var(--muted); font-size: 0.95rem; flex: 1; }
.tags { list-style: none; padding: 0; margin: 0; display: flex; flex-wrap: wrap; gap: 6px; }
.tags li { font-size: 0.8rem; padding: 2px 10px; border-radius: 999px; background: var(--surface-2); color: var(--muted); }
.card-actions { display: flex; flex-wrap: wrap; gap: 8px; }
.card-actions .btn { padding: 8px 12px; min-height: 40px; font-size: 0.92rem; }
.note { color: var(--muted); font-size: 0.85rem; margin-top: 20px; }

.project-head { display: flex; flex-direction: column; gap: 6px; margin-bottom: 18px; }
.project-head h1 { margin: 0; font-size: clamp(1.6rem, 4vw, 2.2rem); text-wrap: balance; }
.project-head .pid { font-size: 0.95rem; }

.demo-section {
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
  box-shadow: var(--shadow); padding: 12px; margin-bottom: 28px;
}
.demo-bar { display: flex; flex-wrap: wrap; align-items: center; gap: 10px; padding: 2px 4px; }
.demo-title { margin: 0; font-size: 1rem; flex: 1; }
.demo-tabs { display: flex; flex-wrap: wrap; gap: 6px; flex: 1; }
.demo-tab {
  padding: 7px 14px; border-radius: 999px; border: 1px solid var(--border); background: var(--surface-2);
  cursor: pointer; font-weight: 600; font-size: 0.92rem; min-height: 38px;
}
.demo-tab[aria-selected="true"] { background: var(--accent); border-color: var(--accent); color: #fff; }
.demo-open { font-size: 0.9rem; font-weight: 600; white-space: nowrap; }
.demo-desc { margin: 6px 4px 10px; color: var(--muted); font-size: 0.92rem; }
.demo-frame { display: block; width: 100%; height: 720px; border: 0; border-radius: 10px; background: var(--surface-2); }
.section-label { font-size: 0.8rem; text-transform: uppercase; letter-spacing: 0.1em; color: var(--accent); margin: 0 0 10px; }

/* ---------- Notes (prose) ---------- */
.prose {
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
  padding: clamp(18px, 4vw, 36px); box-shadow: var(--shadow); overflow-wrap: break-word;
}
.prose > :first-child { margin-top: 0; }
.prose h1 { font-size: clamp(1.6rem, 4vw, 2.1rem); margin-bottom: 0.4em; }
.prose h2 { font-size: 1.35rem; margin-top: 1.8em; padding-bottom: 6px; border-bottom: 2px solid color-mix(in srgb, var(--accent) 30%, transparent); }
.prose h3 { font-size: 1.12rem; margin-top: 1.4em; }
.prose .term { font-weight: 600; }
.prose .term .zh { font-weight: 500; }
.prose blockquote {
  margin: 1.2em 0; padding: 10px 16px; border-left: 4px solid var(--accent);
  background: color-mix(in srgb, var(--accent) 8%, transparent); border-radius: 0 10px 10px 0;
}
.prose blockquote p { margin: 0.3em 0; }
.prose :not(pre) > code { background: var(--code-bg); padding: 1px 6px; border-radius: 6px; }
.prose pre { background: var(--code-bg); padding: 14px 16px; border-radius: 10px; overflow-x: auto; border: 1px solid var(--border); line-height: 1.45; }
.prose img { max-width: 100%; }
.table-wrap { overflow-x: auto; margin: 1em 0; }
.prose table { border-collapse: collapse; width: 100%; font-size: 0.95rem; }
.prose th, .prose td { border: 1px solid var(--border); padding: 8px 10px; text-align: left; vertical-align: top; }
.prose th { background: var(--surface-2); }
.prose .katex-display { overflow-x: auto; overflow-y: hidden; padding: 4px 0; }
.mermaid { display: flex; justify-content: center; margin: 1.2em 0; overflow-x: auto; }
.mermaid svg { max-width: 100%; height: auto; }

.pager { display: grid; grid-template-columns: 1fr 1fr; gap: 10px; margin-top: 18px; }
.pager a {
  display: block; padding: 12px 14px; border-radius: 12px; border: 1px solid var(--border);
  background: var(--surface); text-decoration: none; color: var(--text);
}
.pager a small { display: block; color: var(--muted); }
.pager .next { text-align: right; grid-column: 2; }

/* ---------- hljs ---------- */
.hljs-keyword, .hljs-selector-tag, .hljs-meta .hljs-keyword { color: var(--hl-keyword); }
.hljs-string, .hljs-meta .hljs-string { color: var(--hl-string); }
.hljs-number, .hljs-literal { color: var(--hl-number); }
.hljs-comment { color: var(--hl-comment); font-style: italic; }
.hljs-title, .hljs-title.function_ { color: var(--hl-title); }
.hljs-type, .hljs-built_in { color: var(--hl-type); }
.hljs-meta { color: var(--hl-comment); }

.empty, .error {
  background: var(--surface); border: 1px dashed var(--border); border-radius: var(--radius);
  padding: 24px; text-align: center; color: var(--muted);
}
.error { border-color: var(--bad); color: var(--bad); }

/* ---------- Small screens ---------- */
@media (max-width: 560px) {
  body { font-size: 16px; }
  .brand { font-size: 0; gap: 0; }
  .brand-mark { font-size: 0.8rem; }
  .pager { grid-template-columns: 1fr; }
  .pager .next { grid-column: 1; }
}

/* ---------- Print (formula sheets) ---------- */
@media print {
  .site-header, .site-footer, .crumbs, .no-print { display: none !important; }
  body { background: #fff; color: #000; }
  .prose { border: 0; box-shadow: none; padding: 0; }
}