:root {
  --paper: #faf9f6;
  --surface: #fff;
  --ink: #1b1a17;
  --muted: #6d6962;
  --line: rgba(27, 26, 23, 0.15);
  --line-strong: rgba(27, 26, 23, 0.32);
  --accent: #4338ca;
  --accent-soft: #eceaff;
  --sans: "Aptos", "Helvetica Neue", "PingFang SC", "Hiragino Sans GB", sans-serif;
  --serif: "Songti SC", "STSong", Georgia, serif;
  --mono: "SFMono-Regular", "JetBrains Mono", Consolas, monospace;
}

* { box-sizing: border-box; }
html { overflow-x: hidden; scroll-behavior: smooth; }
body {
  margin: 0;
  color: var(--ink);
  background:
    linear-gradient(90deg, rgba(27, 26, 23, 0.035) 1px, transparent 1px) 0 0 / 96px 100%,
    var(--paper);
  font-family: var(--sans);
  line-height: 1.65;
}
a { color: inherit; text-decoration: none; }
button, input { font: inherit; }
p, h1, h2, h3 { margin: 0; }
.shell { width: min(1200px, calc(100% - 64px)); margin-inline: auto; }
.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
}

.lab-header {
  position: sticky;
  z-index: 20;
  top: 0;
  border-bottom: 1px solid var(--line);
  background: rgba(250, 249, 246, 0.94);
  backdrop-filter: blur(16px);
}
.lab-header-inner {
  display: grid;
  grid-template-columns: 1fr auto 1fr;
  align-items: center;
  min-height: 74px;
}
.lab-header p {
  color: var(--muted);
  font-family: var(--mono);
  font-size: 9px;
  letter-spacing: 0.13em;
}
.home-link, .chapter-link { font-size: 12px; }
.home-link { display: inline-flex; align-items: center; gap: 8px; width: fit-content; }
.home-link span { color: var(--accent); }
.chapter-link { justify-self: end; padding-bottom: 2px; border-bottom: 1px solid var(--line-strong); }

.lab-hero {
  display: grid;
  grid-template-columns: 1fr minmax(320px, 0.55fr);
  gap: 70px;
  align-items: end;
  padding-block: 96px 64px;
}
.eyebrow {
  grid-column: 1 / -1;
  color: var(--accent);
  font-family: var(--mono);
  font-size: 9px;
  letter-spacing: 0.12em;
}
.lab-hero h1 {
  margin-top: 18px;
  font-family: var(--serif);
  font-size: clamp(56px, 7vw, 94px);
  font-weight: 500;
  letter-spacing: -0.055em;
  line-height: 0.98;
}
.lab-lead {
  color: var(--muted);
  font-size: 14px;
  line-height: 1.85;
}
.lab-search {
  grid-column: 1 / -1;
  display: grid;
  grid-template-columns: auto 1fr auto;
  gap: 12px;
  align-items: center;
  margin-top: 18px;
  padding: 14px 16px;
  border: 1px solid var(--line-strong);
  background: var(--surface);
}
.lab-search svg {
  width: 17px;
  fill: none;
  stroke: var(--accent);
  stroke-width: 1.7;
}
.lab-search input {
  min-width: 0;
  padding: 0;
  border: 0;
  outline: 0;
  background: transparent;
  font-size: 13px;
}
.lab-search span {
  color: var(--muted);
  font-family: var(--mono);
  font-size: 9px;
}

.lab-library { padding-bottom: 110px; }
.lab-group {
  display: grid;
  grid-template-columns: 230px 1fr;
  gap: 32px;
  padding-block: 36px;
  border-top: 1px solid var(--line-strong);
}
.lab-group[hidden] { display: none; }
.lab-group > header {
  position: sticky;
  top: 100px;
  align-self: start;
  display: grid;
  grid-template-columns: 30px 1fr;
  gap: 12px;
}
.lab-group > header > span {
  color: var(--accent);
  font-family: var(--mono);
  font-size: 10px;
}
.lab-group > header p {
  color: var(--muted);
  font-family: var(--mono);
  font-size: 8px;
  letter-spacing: 0.1em;
}
.lab-group > header h2 {
  margin: 7px 0 12px;
  font-family: var(--serif);
  font-size: 28px;
  font-weight: 600;
  line-height: 1.15;
}
.lab-group > header small {
  grid-column: 2;
  color: var(--muted);
  font-size: 10px;
}
.lab-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  border-top: 1px solid var(--line);
  border-left: 1px solid var(--line);
}
.lab-card {
  position: relative;
  display: grid;
  grid-template-columns: 30px 1fr;
  gap: 8px 14px;
  min-height: 174px;
  padding: 22px;
  border-right: 1px solid var(--line);
  border-bottom: 1px solid var(--line);
  background: rgba(255, 255, 255, 0.72);
  transition: background 160ms ease, transform 160ms ease;
}
.lab-card:hover { z-index: 1; background: var(--surface); transform: translateY(-2px); }
.lab-card[hidden] { display: none; }
.lab-card-index { color: var(--muted); font-family: var(--mono); font-size: 9px; }
.lab-card h3 {
  padding-right: 24px;
  font-family: var(--serif);
  font-size: 21px;
  font-weight: 600;
}
.lab-card p {
  margin-top: 8px;
  color: var(--muted);
  font-size: 12px;
  line-height: 1.75;
}
.lab-card code {
  grid-column: 2;
  justify-self: start;
  padding-top: 11px;
  color: var(--accent);
  font-family: var(--mono);
  font-size: 9px;
}
.lab-card > i {
  position: absolute;
  top: 20px;
  right: 20px;
  color: var(--accent);
  font-style: normal;
}
.unavailable-note {
  display: grid;
  grid-template-columns: 0.7fr 1fr;
  gap: 50px;
  margin-top: 30px;
  padding: 28px;
  border: 1px dashed var(--line-strong);
}
.unavailable-note p:first-child {
  color: var(--muted);
  font-family: var(--mono);
  font-size: 9px;
  letter-spacing: 0.1em;
}
.unavailable-note h2 {
  margin-top: 8px;
  font-family: var(--serif);
  font-size: 22px;
  font-weight: 600;
}
.unavailable-note > p {
  color: var(--muted);
  font-size: 12px;
  line-height: 1.8;
}
.unavailable-note code { color: var(--ink); }
.empty-state {
  width: min(600px, calc(100% - 40px));
  margin: 0 auto 100px;
  padding: 44px 24px;
  border: 1px dashed var(--line-strong);
  text-align: center;
}
.empty-state strong { font-family: var(--serif); font-size: 25px; }
.empty-state p { margin: 8px 0 18px; color: var(--muted); font-size: 12px; }
.empty-state button {
  padding: 8px 13px;
  border: 1px solid var(--ink);
  background: transparent;
  font-size: 11px;
  cursor: pointer;
}
.lab-footer {
  border-top: 1px solid var(--line-strong);
  background: var(--ink);
  color: var(--paper);
}
.lab-footer .shell {
  display: flex;
  justify-content: space-between;
  align-items: center;
  min-height: 110px;
  font-size: 10px;
}
.lab-footer p { color: rgba(250, 249, 246, 0.58); font-family: var(--mono); }
.lab-footer a { border-bottom: 1px solid rgba(250, 249, 246, 0.42); }

@media (max-width: 900px) {
  .lab-hero { grid-template-columns: 1fr; gap: 26px; padding-block: 72px 48px; }
  .lab-group { grid-template-columns: 1fr; gap: 18px; }
  .lab-group > header { position: static; }
  .lab-group > header small { margin-top: -6px; }
}

@media (max-width: 640px) {
  .shell { width: calc(100% - 28px); }
  .lab-header-inner { grid-template-columns: 1fr auto; min-height: 66px; }
  .lab-header p { display: none; }
  .lab-hero h1 { font-size: 55px; }
  .lab-search { grid-template-columns: auto 1fr; }
  .lab-search span { grid-column: 1 / -1; }
  .lab-grid { grid-template-columns: 1fr; }
  .lab-card { min-height: 150px; }
  .unavailable-note { grid-template-columns: 1fr; gap: 18px; padding: 22px; }
  .lab-footer .shell { align-items: flex-start; flex-direction: column; justify-content: center; gap: 10px; }
}