:root {
  color-scheme: light;
  --ink: #14233b;
  --body: #26364d;
  --muted: #627084;
  --line: #d9dee7;
  --paper: #f7f5ef;
  --card: #ffffff;
  --sunken: #eef1f5;
  --accent: #d66a2f;
  --accent-soft: #f8e5d8;
  --pass: #176b45;
  --pass-bg: #e4f3eb;
  --fail: #9f2f2f;
  --fail-bg: #f9e5e5;
  --info: #315779;
  --info-bg: #e7eef6;
  --shadow: 0 16px 36px rgba(20, 35, 59, 0.08);
  font-family: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  background: var(--paper);
  color: var(--body);
  line-height: 1.6;
}
a { color: #244f7c; text-underline-offset: 0.18em; }
a:hover { color: var(--accent); }
button, input, select { font: inherit; }
button {
  border: 0;
  border-radius: 0.65rem;
  padding: 0.72rem 1rem;
  background: var(--ink);
  color: white;
  font-weight: 700;
  cursor: pointer;
}
button:hover { background: #233c61; }
button.secondary {
  background: transparent;
  color: var(--ink);
  border: 1px solid rgba(20, 35, 59, 0.28);
}
button.secondary:hover { border-color: var(--ink); background: rgba(255,255,255,.6); }
button:focus-visible, input:focus-visible, select:focus-visible, summary:focus-visible, a:focus-visible {
  outline: 3px solid rgba(214, 106, 47, 0.42);
  outline-offset: 3px;
}
code, pre, .eyebrow, .lab-number {
  font-family: "SFMono-Regular", Consolas, "Liberation Mono", monospace;
}
code {
  background: rgba(20,35,59,.07);
  border-radius: .35rem;
  padding: .08rem .28rem;
}
pre {
  margin: .8rem 0;
  padding: .9rem 1rem;
  overflow-x: auto;
  white-space: pre-wrap;
  overflow-wrap: anywhere;
  background: #17253a;
  color: #f4f7fb;
  border-radius: .65rem;
  font-size: .86rem;
}

.shell { width: min(1120px, calc(100% - 2rem)); margin-inline: auto; }
.skip-link {
  position: absolute;
  left: .75rem;
  top: -4rem;
  background: white;
  color: var(--ink);
  padding: .7rem 1rem;
  z-index: 100;
}
.skip-link:focus { top: .75rem; }
.hero {
  background: linear-gradient(180deg, #eef1f5 0%, var(--paper) 100%);
  border-bottom: 1px solid var(--line);
  padding: 4.5rem 0 3rem;
}
.eyebrow {
  margin: 0 0 .55rem;
  color: var(--accent);
  text-transform: uppercase;
  letter-spacing: .12em;
  font-size: .74rem;
  font-weight: 800;
}
h1, h2, h3 { color: var(--ink); line-height: 1.14; }
h1 { margin: 0; max-width: 800px; font-size: clamp(2.35rem, 6vw, 4.8rem); letter-spacing: -.035em; }
h2 { font-size: clamp(1.7rem, 3vw, 2.5rem); margin: 0; }
h3 { font-size: 1.35rem; margin: 0 0 .55rem; }
.lede { max-width: 760px; font-size: clamp(1.05rem, 2.2vw, 1.35rem); color: var(--muted); }
.invariant { display: flex; flex-wrap: wrap; gap: .55rem; margin: 1.4rem 0; }
.invariant code { background: var(--card); border: 1px solid var(--line); padding: .45rem .65rem; }
.safety-note {
  max-width: 880px;
  padding: 1rem 1.1rem;
  border-left: 4px solid var(--accent);
  background: rgba(255,255,255,.7);
}
.jump-nav { display: flex; flex-wrap: wrap; gap: .75rem 1rem; margin-top: 1.35rem; }
.jump-nav a { font-weight: 700; }

main > section { padding: 4rem 0; }
.section-heading { max-width: 820px; margin-bottom: 1.6rem; }
.section-heading > p:last-child { color: var(--muted); }
.layer-grid { display: grid; grid-template-columns: repeat(5, 1fr); gap: .8rem; }
.layer-grid article {
  min-height: 140px;
  display: flex;
  flex-direction: column;
  gap: .5rem;
  padding: 1rem;
  border: 1px solid var(--line);
  border-radius: .8rem;
  background: var(--card);
}
.layer-grid strong { color: var(--ink); }
.layer-grid span { color: var(--muted); font-size: .92rem; }

.lab-card {
  display: grid;
  grid-template-columns: 72px 1fr;
  gap: 1.25rem;
  margin: 1.25rem 0;
  padding: 1.45rem;
  border: 1px solid var(--line);
  border-radius: 1rem;
  background: var(--card);
  box-shadow: var(--shadow);
  scroll-margin-top: 1rem;
}
.lab-card.deep { border-top: 4px solid var(--accent); }
.lab-number {
  display: grid;
  place-items: center;
  width: 56px;
  height: 56px;
  border-radius: 999px;
  background: var(--accent-soft);
  color: #7d3516;
  font-weight: 900;
}
.question { font-size: 1.05rem; color: var(--ink); }
.scenario {
  margin: 1rem 0;
  padding: .85rem 1rem;
  background: var(--sunken);
  border-radius: .7rem;
}
fieldset {
  margin: 1rem 0;
  border: 1px solid var(--line);
  border-radius: .7rem;
  padding: .8rem 1rem 1rem;
}
legend { color: var(--ink); font-weight: 700; padding: 0 .35rem; }
fieldset label { margin-right: 1rem; display: inline-flex; gap: .4rem; align-items: center; }
.check-row { display: flex; align-items: flex-start; gap: .55rem; margin: 1rem 0; }
.result {
  margin-top: 1rem;
  padding: .8rem 1rem;
  border-radius: .65rem;
  background: var(--info-bg);
  color: var(--info);
  border-left: 4px solid currentColor;
}
.result.pass { background: var(--pass-bg); color: var(--pass); }
.result.fail { background: var(--fail-bg); color: var(--fail); }
.result.info { background: var(--info-bg); color: var(--info); }
.comparison, .evidence-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: .8rem;
  margin-top: 1rem;
}
.comparison > div, .evidence-grid > div {
  border: 1px solid var(--line);
  border-radius: .7rem;
  background: var(--sunken);
  padding: .9rem;
}
.comparison span, .evidence-grid span { display: block; color: var(--muted); font-size: .78rem; text-transform: uppercase; letter-spacing: .08em; margin-bottom: .35rem; }
.comparison strong { display: block; color: var(--ink); }
.evidence-grid { grid-template-columns: repeat(3, minmax(0, 1fr)); }
.evidence-grid code { display: inline-block; }
.code-pair { margin: 1rem 0; }
.code-pair select { width: min(100%, 360px); }
select, input[type="text"] {
  width: 100%;
  border: 1px solid #b8c0cc;
  border-radius: .55rem;
  padding: .68rem .75rem;
  background: white;
  color: var(--ink);
}
details { margin-top: 1rem; border-top: 1px solid var(--line); padding-top: .9rem; }
summary { color: var(--ink); font-weight: 750; cursor: pointer; }
.copy-button { margin-top: .25rem; }

.form-grid { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: .9rem; margin: 1rem 0; }
.form-grid.single { grid-template-columns: 1fr; }
.form-grid label { color: var(--ink); font-weight: 700; font-size: .9rem; }
.form-grid input, .form-grid select { margin-top: .35rem; font-weight: 400; }
.output { min-height: 88px; }

.export-panel {
  padding: 1.4rem !important;
  margin: 2rem 0 4rem;
  border: 1px solid var(--line);
  border-radius: 1rem;
  background: var(--sunken);
}
.button-row { display: flex; flex-wrap: wrap; gap: .65rem; margin-top: 1rem; }
.context-links { border-top: 1px solid var(--line); }
footer { border-top: 1px solid var(--line); padding: 1.5rem 0 2.5rem; color: var(--muted); font-size: .9rem; }

@media (max-width: 840px) {
  .layer-grid { grid-template-columns: repeat(2, 1fr); }
  .evidence-grid { grid-template-columns: 1fr; }
}

@media (max-width: 620px) {
  .hero { padding-top: 3.2rem; }
  .lab-card { grid-template-columns: 1fr; padding: 1rem; }
  .lab-number { width: 44px; height: 44px; }
  .layer-grid, .form-grid, .comparison { grid-template-columns: 1fr; }
  fieldset label { display: flex; margin: .55rem 0; }
  button { width: 100%; }
  .jump-nav a { width: 100%; }
}