/* ========== Design tokens ========== */
:root {
  --bg: #ffffff;
  --fg: #0b1220;
  --muted: #5b6478;
  --card: #fafbff;
  --border: #e7e9f2;
  --brand: #4f46e5;            /* indigo-600 */
  --brand-fg: #eef2ff;
  --accent: #22c55e;           /* green-500 */
  --link: #3b82f6;             /* blue-500 */

  --shadow-sm: 0 1px 2px rgba(15, 23, 42, .06);
  --shadow-md: 0 6px 18px rgba(15, 23, 42, .08);

  --radius: 14px;
  --radius-sm: 10px;

  color-scheme: light;
}

@media (prefers-color-scheme: dark) {
  :root { color-scheme: dark; }
  :root:not([data-theme="light"]) {
    --bg: #0b1220;
    --fg: #e8ecf8;
    --muted: #9aa3b2;
    --card: #121a2c;
    --border: #202a42;
    --brand: #8b87ff;
    --brand-fg: #141532;
    --accent: #34d399;
    --link: #60a5fa;
    --shadow-sm: 0 1px 2px rgba(0,0,0,.35);
    --shadow-md: 0 10px 26px rgba(0,0,0,.35);
  }
}

/* manual override */
:root[data-theme="dark"] {
  --bg: #0b1220;
  --fg: #e8ecf8;
  --muted: #9aa3b2;
  --card: #121a2c;
  --border: #202a42;
  --brand: #8b87ff;
  --brand-fg: #141532;
  --accent: #34d399;
  --link: #60a5fa;
}

/* ========== Base ========== */
* { box-sizing: border-box; }
html, body { height: 100%; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  font-family: Inter, system-ui, -apple-system, Segoe UI, Roboto, sans-serif;
  background: var(--bg);
  color: var(--fg);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

a { color: var(--link); text-decoration: none; }
a:hover { text-decoration: underline; }

.wrap { max-width: 1100px; margin: 0 auto; padding: 0 20px; }

/* ========== Header / Footer ========== */
.site-header {
  position: sticky; top: 0; z-index: 50;
  backdrop-filter: saturate(180%) blur(8px);
  background: color-mix(in oklab, var(--bg) 86%, transparent);
  border-bottom: 1px solid var(--border);
}
.site-header .wrap {
  display:flex; align-items:center; justify-content:space-between;
  min-height: 64px;
}
.title { margin: 0; font-size: clamp(1.25rem, 2vw + .5rem, 2rem); font-weight: 700; letter-spacing: .2px; }
.meta { display:flex; gap:.5rem; align-items:center; }
.btn.subtle {
  border: 1px solid var(--border);
  background: var(--card);
  color: var(--fg);
  border-radius: 10px;
  padding: .45rem .6rem;
  cursor: pointer;
  box-shadow: var(--shadow-sm);
}
.btn.subtle:hover { transform: translateY(-1px); box-shadow: var(--shadow-md); }

.site-footer { border-top: 1px solid var(--border); margin-top: 48px; }
.site-footer .wrap { padding: 18px 20px; color: var(--muted); }

/* ========== Layout ========== */
.page {
  display: grid;
  grid-template-columns: 270px 1fr;
  gap: 28px;
  max-width: 1200px;
  margin: 24px auto;
  padding: 0 20px;
}
@media (max-width: 900px) {
  .page { grid-template-columns: 1fr; }
  .sidebar { position: static; top: auto; }
}

.sidebar {
  position: sticky; top: 84px; align-self: start;
  max-height: calc(100dvh - 100px); overflow: auto;
}
.toc {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: var(--shadow-sm);
  padding: 14px;
}
.toc__title {
  font-weight: 600; letter-spacing: .2px; color: var(--muted);
  font-size: .9rem; margin: 2px 4px 8px;
  text-transform: uppercase;
}
.toc__nav ul { list-style: none; margin: 0; padding: 0; }
.toc__nav li { margin: 6px 0; }
.toc__nav a {
  display: block; padding: 6px 8px; border-radius: 8px;
  color: var(--fg); text-decoration: none;
}
.toc__nav a:hover { background: color-mix(in oklab, var(--brand) 12%, transparent); }
.toc__nav a.active { background: color-mix(in oklab, var(--brand) 18%, transparent); color: var(--brand); }

/* ========== Content Cards ========== */
.content { display: grid; gap: 18px; }
.subtopic {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: var(--shadow-sm);
  padding: 18px 18px 2px;
}
.subtopic:hover { box-shadow: var(--shadow-md); transition: box-shadow .2s ease; }

.subtopic h2 {
  margin: 0 0 8px;
  font-size: clamp(1.05rem, .7vw + .9rem, 1.25rem);
  line-height: 1.25;
  display: flex; align-items: center; gap: .5rem;
}
.subtopic h2 .anchor {
  margin-left: auto; font-size: .9rem; line-height: 1;
  border: 1px solid var(--border); background: transparent; color: var(--muted);
  border-radius: 8px; padding: 2px 6px; cursor: pointer;
}
.subtopic h2 .anchor:hover { color: var(--fg); }
.subtopic h2 .anchor.copied { color: var(--accent); border-color: var(--accent); }

.subtopic p { margin: .45rem 0 .75rem; color: var(--fg); }

/* Lists: nicer bullets & spacing */
.subtopic ul { margin: .45rem 0 .9rem 1.2rem; padding-left: 1.1rem; }
.subtopic li { margin: .35rem 0; }
.subtopic ul li::marker { color: var(--brand); }

/* ========== Tables ========== */
.subtopic table {
  border-collapse: separate;
  border-spacing: 0;
  margin: .8rem 0 1.2rem;
  width: 100%;
  overflow: hidden;
  border-radius: var(--radius-sm);
  border: 1px solid var(--border);
  background: var(--bg);
}
.subtopic thead th {
  background: color-mix(in oklab, var(--brand) 14%, var(--card));
  color: var(--fg);
  border-bottom: 1px solid var(--border);
  text-align: left; padding: .6rem .7rem; font-weight: 600;
}
.subtopic tbody td { padding: .55rem .7rem; border-top: 1px solid var(--border); }
.subtopic tbody tr:nth-child(odd) td {
  background: color-mix(in oklab, var(--card) 85%, transparent);
}
.center { text-align: center; }
.right { text-align: right; }

/* ========== Code ========== */
code, pre {
  font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  font-size: .95em;
}
code {
  background: color-mix(in oklab, var(--card) 80%, transparent);
  border: 1px solid var(--border);
  border-radius: 6px; padding: 0 .3rem;
}

/* ========== Helpers ========== */
hr { border: 0; height: 1px; background: var(--border); margin: 1rem 0; }