:root {
  --bg: #fbfbf9;
  --panel: #ffffff;
  --ink: #1a1a1a;
  --muted: #5b5b5b;
  --line: #e4e2dc;
  --accent: #1f4ed8;
  --accent-soft: rgba(31, 78, 216, 0.12);
  --warn: #c2410c;
  --good: #15803d;
  --bad: #b91c1c;
  --maxw: 860px;
}

* { box-sizing: border-box; }

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

body {
  margin: 0;
  background: var(--bg);
  color: var(--ink);
  font: 16px/1.65 ui-serif, Georgia, "Times New Roman", serif;
  -webkit-font-smoothing: antialiased;
}

.wrap { max-width: var(--maxw); margin: 0 auto; padding: 0 20px; }

header.site {
  border-bottom: 1px solid var(--line);
  background: var(--panel);
}
header.site .wrap {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  padding-top: 14px;
  padding-bottom: 14px;
  flex-wrap: wrap;
  gap: 8px;
}
header.site a.brand {
  font-family: ui-sans-serif, system-ui, sans-serif;
  font-weight: 700;
  font-size: 18px;
  letter-spacing: -0.01em;
  color: var(--ink);
  text-decoration: none;
}
header.site nav a {
  color: var(--muted);
  text-decoration: none;
  font-family: ui-sans-serif, system-ui, sans-serif;
  font-size: 14px;
  margin-left: 16px;
}
header.site nav a:hover { color: var(--accent); }

main { padding: 36px 0 80px; }

h1, h2, h3 {
  font-family: ui-sans-serif, system-ui, -apple-system, sans-serif;
  line-height: 1.25;
  letter-spacing: -0.02em;
}
h1 { font-size: 2.0rem; margin: 0 0 6px; }
h2 { font-size: 1.4rem; margin: 2.2em 0 0.5em; }
h3 { font-size: 1.1rem; margin: 1.6em 0 0.4em; }
.subtitle { color: var(--muted); font-style: italic; font-size: 1.05rem; margin: 0 0 1.6em; }

p { margin: 0 0 1em; }
a { color: var(--accent); }

.lead { font-size: 1.12rem; }

ul, ol { padding-left: 1.3em; }
li { margin: 0.25em 0; }

code, kbd, .mono {
  font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  font-size: 0.9em;
}
code { background: #f0efe9; padding: 0.1em 0.35em; border-radius: 4px; }
pre {
  background: #f7f6f1; border: 1px solid var(--line); border-radius: 8px;
  padding: 14px 16px; overflow-x: auto; line-height: 1.5; margin: 1em 0;
}
pre code { background: none; padding: 0; font-size: 13px; }

blockquote {
  margin: 1.4em 0;
  padding: 0.6em 1.1em;
  border-left: 3px solid var(--accent);
  background: var(--accent-soft);
  font-style: italic;
}
blockquote p:last-child { margin-bottom: 0; }

.tag {
  display: inline-block;
  font-family: ui-sans-serif, system-ui, sans-serif;
  font-size: 11px;
  font-weight: 600;
  letter-spacing: 0.04em;
  text-transform: uppercase;
  padding: 2px 8px;
  border-radius: 999px;
  background: var(--accent-soft);
  color: var(--accent);
  vertical-align: middle;
}

/* ---- Demo cards on the landing page ---- */
.cards { display: grid; grid-template-columns: 1fr 1fr; gap: 16px; margin: 1.5em 0; }
@media (max-width: 640px) {
  .cards { grid-template-columns: 1fr; }
  header.site .wrap { flex-direction: column; align-items: flex-start; }
  header.site nav { display: flex; flex-wrap: wrap; gap: 2px 14px; margin-top: 2px; }
  header.site nav a { margin-left: 0; font-size: 13px; }
}
.card {
  display: block;
  border: 1px solid var(--line);
  border-radius: 10px;
  padding: 18px 20px;
  background: var(--panel);
  text-decoration: none;
  color: var(--ink);
  transition: border-color 0.15s, transform 0.15s, box-shadow 0.15s;
}
.card:hover { border-color: var(--accent); transform: translateY(-2px); box-shadow: 0 6px 20px rgba(0,0,0,0.05); }
.card .num { font-family: ui-monospace, monospace; color: var(--accent); font-size: 13px; }
.card h3 { margin: 4px 0 6px; font-size: 1.08rem; }
.card p { margin: 0; color: var(--muted); font-size: 0.95rem; line-height: 1.5; }

/* ---- Demo page apparatus ---- */
.demo {
  border: 1px solid var(--line);
  border-radius: 12px;
  background: var(--panel);
  padding: 18px;
  margin: 1.5em 0;
}
.canvas-box { position: relative; width: 100%; }
canvas { width: 100%; display: block; border-radius: 8px; }
.canvas-box.tall canvas { height: 380px; }
.canvas-box.med canvas { height: 300px; }
.canvas-box.short canvas { height: 200px; }

.controls {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: 14px 22px;
  margin: 16px 2px 4px;
  font-family: ui-sans-serif, system-ui, sans-serif;
  font-size: 14px;
}
.control { display: flex; flex-direction: column; gap: 4px; }
.control label { color: var(--muted); display: flex; justify-content: space-between; }
.control label .val { color: var(--ink); font-family: ui-monospace, monospace; }
.control input[type=range] { width: 100%; accent-color: var(--accent); }
.control.checkbox { flex-direction: row; align-items: center; gap: 8px; }
.control.checkbox input { accent-color: var(--accent); }

button.btn {
  font-family: ui-sans-serif, system-ui, sans-serif;
  font-size: 14px;
  padding: 7px 14px;
  border: 1px solid var(--line);
  background: var(--panel);
  border-radius: 8px;
  cursor: pointer;
  color: var(--ink);
}
button.btn:hover { border-color: var(--accent); color: var(--accent); }

/* readouts: big numbers under a chart */
.readouts {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(140px, 1fr));
  gap: 12px;
  margin: 16px 0 2px;
}
.readout {
  border: 1px solid var(--line);
  border-radius: 10px;
  padding: 12px 14px;
  background: #fcfcfb;
  text-align: center;
}
.readout .k {
  font-family: ui-sans-serif, system-ui, sans-serif;
  font-size: 12px;
  color: var(--muted);
  text-transform: uppercase;
  letter-spacing: 0.03em;
}
.readout .v {
  font-family: ui-monospace, monospace;
  font-size: 1.55rem;
  margin-top: 4px;
}
.readout .v.good { color: var(--good); }
.readout .v.warn { color: var(--warn); }
.readout .v.bad { color: var(--bad); }

.takeaway {
  border-left: 3px solid var(--warn);
  background: rgba(194, 65, 12, 0.07);
  padding: 0.7em 1.1em;
  border-radius: 0 8px 8px 0;
  margin: 1.4em 0;
}
.takeaway strong { font-family: ui-sans-serif, system-ui, sans-serif; }

.prevnext {
  display: flex;
  justify-content: space-between;
  gap: 12px;
  margin-top: 3em;
  border-top: 1px solid var(--line);
  padding-top: 1.2em;
  font-family: ui-sans-serif, system-ui, sans-serif;
  font-size: 14px;
}
.prevnext a { text-decoration: none; }
.prevnext .spacer { flex: 1; }

footer.site {
  border-top: 1px solid var(--line);
  color: var(--muted);
  font-family: ui-sans-serif, system-ui, sans-serif;
  font-size: 13px;
  padding: 24px 0 40px;
}
footer.site .wrap { display: flex; justify-content: space-between; flex-wrap: wrap; gap: 8px; }

.refs { font-size: 0.92rem; color: var(--muted); }
.refs li { margin: 0.4em 0; }

.note { font-size: 0.92rem; color: var(--muted); }

/* MathJax shouldn't overflow on mobile */
mjx-container { overflow-x: auto; overflow-y: hidden; max-width: 100%; }