:root {
  --bg: #f7f8fa;
  --paper: #ffffff;
  --ink: #17191d;
  --muted: #5d6572;
  --line: #d9dee7;
  --accent: #1d4ed8;
  --accent-soft: #e8efff;
  --code: #f2f4f7;
}
@media (prefers-color-scheme: dark) {
  :root {
    --bg: #101217;
    --paper: #171a21;
    --ink: #eef1f6;
    --muted: #aeb6c3;
    --line: #303642;
    --accent: #8db2ff;
    --accent-soft: #202e4f;
    --code: #11141a;
  }
}
* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  background: var(--bg);
  color: var(--ink);
  font-family: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  line-height: 1.63;
}
body > header, body > main, body > nav, body > footer {
  max-width: 1080px;
  margin-left: auto;
  margin-right: auto;
}
body > main, body > header {
  background: var(--paper);
  padding: clamp(24px, 5vw, 72px);
}
body > header { margin-top: 32px; border-radius: 18px 18px 0 0; }
body > main { margin-bottom: 48px; border-radius: 0 0 18px 18px; }
#TOC {
  position: sticky;
  top: 0;
  z-index: 3;
  max-height: 44vh;
  overflow: auto;
  background: color-mix(in srgb, var(--paper) 96%, transparent);
  backdrop-filter: blur(12px);
  border: 1px solid var(--line);
  padding: 16px 24px;
}
#TOC ul { columns: 2; column-gap: 36px; margin: 0; padding-left: 20px; }
#TOC li { break-inside: avoid; margin: 2px 0; }
#TOC a { color: var(--muted); text-decoration: none; font-size: 0.88rem; }
#TOC a:hover, #TOC a:focus { color: var(--accent); text-decoration: underline; }
h1, h2, h3, h4 { line-height: 1.16; scroll-margin-top: 48vh; }
h1 { font-size: clamp(2.4rem, 7vw, 5.2rem); letter-spacing: -0.055em; margin: 0 0 0.2em; }
h2 { font-size: clamp(1.7rem, 4vw, 2.7rem); letter-spacing: -0.03em; margin-top: 2.2em; border-top: 1px solid var(--line); padding-top: 0.9em; }
h3 { font-size: 1.45rem; margin-top: 1.7em; }
h4 { font-size: 1.15rem; margin-top: 1.4em; }
p, li { max-width: 82ch; }
a { color: var(--accent); }
blockquote {
  margin-left: 0;
  padding: 0.8rem 1.2rem;
  background: var(--accent-soft);
  border-left: 4px solid var(--accent);
}
table { width: 100%; border-collapse: collapse; display: block; overflow-x: auto; margin: 1.3rem 0; }
th, td { border: 1px solid var(--line); padding: 0.65rem 0.75rem; vertical-align: top; min-width: 9rem; }
th { background: var(--accent-soft); text-align: left; }
pre {
  overflow-x: auto;
  padding: 1rem;
  background: var(--code);
  border: 1px solid var(--line);
  border-radius: 10px;
}
code { font-family: "SFMono-Regular", Consolas, "Liberation Mono", monospace; font-size: 0.91em; }
:not(pre) > code { padding: 0.12rem 0.3rem; background: var(--code); border-radius: 4px; }
hr { border: 0; border-top: 1px solid var(--line); margin: 3rem 0; }
.math.display { overflow-x: auto; padding: 0.4rem 0; }
.subtitle { color: var(--muted); font-size: 1.15rem; }
@media (max-width: 720px) {
  #TOC { position: relative; max-height: none; }
  #TOC ul { columns: 1; }
  body > header { margin-top: 0; border-radius: 0; }
  body > main { border-radius: 0; }
}
@media print {
  :root { --bg: white; --paper: white; --ink: black; --muted: #444; --line: #aaa; --accent-soft: #eee; }
  #TOC { position: static; max-height: none; page-break-after: always; }
  body > header, body > main { max-width: none; padding: 0; margin: 0; }
  h1, h2, h3 { page-break-after: avoid; }
  table, pre, blockquote { page-break-inside: avoid; }
}