:root {
  --ink: #f5f7f5;
  --muted: #abb5b2;
  --dim: #788480;
  --base: #080c0d;
  --surface: #101617;
  --surface-2: #151d1e;
  --line: #293436;
  --line-strong: #465457;
  --amber: #f3b85b;
  --cyan: #6fd8d2;
  --red: #ff7c74;
  --green: #9bd47d;
  --violet: #b7a2ed;
  --mono: "Cascadia Code", "SFMono-Regular", Consolas, monospace;
  --display: "Microsoft YaHei UI", "PingFang SC", sans-serif;
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  color: var(--ink);
  background:
    linear-gradient(rgba(255,255,255,.017) 1px, transparent 1px),
    linear-gradient(90deg, rgba(255,255,255,.017) 1px, transparent 1px),
    var(--base);
  background-size: 42px 42px;
  font: 17px/1.7 var(--display);
}
a { color: inherit; }
button, select { font: inherit; }
button:focus-visible, select:focus-visible, a:focus-visible {
  outline: 3px solid rgba(243,184,91,.72);
  outline-offset: 3px;
}

.site-header {
  min-height: 68px;
  padding: 0 clamp(20px, 5vw, 72px);
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 24px;
  border-bottom: 1px solid var(--line);
  background: rgba(8,12,13,.94);
  backdrop-filter: blur(16px);
  position: sticky;
  top: 0;
  z-index: 20;
}
.brand { display: flex; align-items: center; gap: 12px; font: 700 13px var(--mono); letter-spacing: .12em; text-decoration: none; }
.brand-mark { width: 30px; height: 30px; display: grid; place-items: center; color: var(--base); background: var(--amber); font-weight: 900; }
nav { display: flex; align-items: center; gap: 24px; }
nav a { color: var(--muted); font-size: 15px; text-decoration: none; }
nav a:hover, nav a:focus-visible { color: var(--ink); }
.github-link { color: var(--ink); }

main { width: min(1680px, 100%); margin: 0 auto; }
.hero {
  min-height: 500px;
  padding: clamp(72px, 10vw, 150px) clamp(22px, 6vw, 96px) 72px;
  display: grid;
  grid-template-columns: minmax(0, 1.35fr) minmax(300px, .65fr);
  align-items: end;
  gap: 64px;
  border-bottom: 1px solid var(--line);
  background:
    radial-gradient(circle at 77% 28%, rgba(111,216,210,.08), transparent 26%),
    linear-gradient(135deg, transparent 0 66%, rgba(243,184,91,.035) 66% 67%, transparent 67%);
}
.eyebrow, .section-kicker, .panel-label {
  margin: 0;
  color: var(--amber);
  font: 700 12px/1.35 var(--mono);
  letter-spacing: .14em;
  text-transform: uppercase;
}
.hero h1 { margin: 20px 0 26px; font-size: clamp(52px, 7vw, 106px); line-height: .98; letter-spacing: -.06em; }
.hero h1 em { color: var(--amber); font-style: normal; }
.hero-intro { max-width: 820px; margin: 0; color: var(--muted); font-size: clamp(18px, 2vw, 24px); }
.hero-rule { padding: 26px; border: 1px solid var(--line-strong); border-left: 4px solid var(--cyan); background: var(--surface); }
.hero-rule span { color: var(--dim); font: 700 12px var(--mono); letter-spacing: .12em; }
.hero-rule strong { display: block; margin: 10px 0; color: var(--cyan); font-size: 21px; }
.hero-rule p { margin: 0; color: var(--muted); font-size: 15px; }

.model, .boundaries, .decision-matrix { padding: 64px clamp(20px, 5vw, 72px); }
.section-heading { display: flex; justify-content: space-between; align-items: end; gap: 40px; margin-bottom: 34px; }
.section-heading h2 { margin: 6px 0 0; font-size: clamp(30px, 4vw, 50px); line-height: 1.12; }
.section-heading > p { max-width: 600px; margin: 0; color: var(--muted); }
.model-grid, .boundary-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 16px; }
.model-grid article, .boundary-grid article {
  min-width: 0;
  padding: 26px;
  border: 1px solid var(--line);
  background: var(--surface);
}
.model-grid span, .boundary-grid span { color: var(--cyan); font: 700 12px var(--mono); letter-spacing: .1em; }
.model-grid h3, .boundary-grid h3 { margin: 16px 0 8px; font-size: 24px; }
.model-grid p, .boundary-grid p { margin: 0; color: var(--muted); }
.model-grid code { display: block; margin-top: 20px; padding: 12px; overflow-wrap: anywhere; color: var(--amber); border: 1px solid var(--line); background: #080c0d; font: 14px/1.5 var(--mono); }

.lab { margin: 0 clamp(16px, 3vw, 48px); border: 1px solid var(--line-strong); background: var(--surface); }
.lab-toolbar { display: grid; grid-template-columns: 1fr auto; border-bottom: 1px solid var(--line); }
.scenario-tabs { display: grid; grid-template-columns: repeat(6, minmax(128px, 1fr)); overflow-x: auto; }
.scenario-tab {
  min-height: 82px;
  padding: 15px 16px;
  color: var(--muted);
  text-align: left;
  border: 0;
  border-right: 1px solid var(--line);
  background: transparent;
  cursor: pointer;
}
.scenario-tab small { display: block; margin-bottom: 6px; color: var(--dim); font: 700 11px var(--mono); letter-spacing: .08em; }
.scenario-tab span { font-weight: 700; }
.scenario-tab:hover { background: var(--surface-2); color: var(--ink); }
.scenario-tab.is-active { color: var(--ink); box-shadow: inset 0 -3px var(--amber); background: #181c1a; }
.scenario-tab.is-active small { color: var(--amber); }
.step-readout { min-width: 136px; padding: 14px 20px; display: grid; place-content: center; text-align: right; }
.step-readout span { color: var(--dim); font: 700 12px var(--mono); letter-spacing: .1em; }
.step-readout strong { font: 700 18px var(--mono); }

.route-strip { display: grid; grid-template-columns: repeat(4, 1fr); border-bottom: 1px solid var(--line); }
.route-node { min-height: 78px; padding: 13px 18px; display: grid; grid-template-columns: auto 1fr; column-gap: 12px; align-content: center; border-right: 1px solid var(--line); color: var(--dim); }
.route-node:last-child { border-right: 0; }
.route-node b { grid-row: 1 / 3; align-self: center; font: 800 22px var(--mono); }
.route-node span { color: var(--muted); font-weight: 700; }
.route-node small { font: 12px var(--mono); }
.route-node.is-current { background: #171b18; box-shadow: inset 0 -3px var(--cyan); }
.route-node.is-current b, .route-node.is-current span { color: var(--cyan); }

.lab-grid { display: grid; grid-template-columns: minmax(280px, .78fr) minmax(470px, 1.42fr) minmax(350px, 1fr); }
.explain-panel, .state-panel, .code-panel { min-width: 0; padding: clamp(22px, 3vw, 36px); }
.explain-panel, .state-panel { border-right: 1px solid var(--line); }
.explain-panel { display: flex; flex-direction: column; gap: 18px; }
.phase { margin: 24px 0 8px; color: var(--cyan); font: 700 13px var(--mono); letter-spacing: .12em; }
.explain-panel h2, .panel-head h2, .code-head h2 { margin: 0; line-height: 1.2; }
.explain-panel h2 { font-size: 30px; }
.step-copy { margin-bottom: 0; color: var(--muted); }
.decision-box, .reason-box, .cost-box { padding: 15px 17px; border: 1px solid var(--line); background: #0b1011; }
.decision-box { border-left: 3px solid var(--cyan); }
.reason-box { border-left: 3px solid var(--amber); }
.cost-box { border-left: 3px solid var(--violet); }
.decision-box span, .reason-box span, .cost-box span, .result-banner span { color: var(--dim); font: 700 12px var(--mono); letter-spacing: .1em; }
.decision-box p, .reason-box p, .cost-box p { margin: 6px 0 0; color: var(--muted); }
.result-banner { margin-top: auto; padding: 14px 16px; display: flex; justify-content: space-between; gap: 14px; border: 1px solid var(--cyan); }
.result-banner[data-tone="success"] { border-color: var(--green); color: var(--green); }
.result-banner[data-tone="failed"] { border-color: var(--red); color: var(--red); }
.result-banner[data-tone="queued"] { border-color: var(--amber); color: var(--amber); }
.result-banner[data-tone="warning"] { border-color: var(--violet); color: var(--violet); }

.panel-head, .code-head { display: flex; justify-content: space-between; align-items: start; gap: 18px; }
.panel-head h2, .code-head h2 { margin-top: 6px; font-size: 22px; }
.scenario-note { max-width: 260px; color: var(--amber); font: 600 12px/1.5 var(--mono); text-align: right; }
.ledger-board { margin-top: 24px; display: grid; grid-template-columns: 150px 1fr; border: 1px solid var(--line); background: #0b1011; }
.tag-summary { padding: 18px; display: flex; flex-direction: column; justify-content: center; border-right: 1px solid var(--line); }
.tag-summary span { color: var(--dim); font: 700 11px var(--mono); letter-spacing: .1em; }
.tag-summary strong { margin: 8px 0 14px; font-size: 21px; }
.tag-summary em { width: fit-content; padding: 4px 9px; color: var(--red); border: 1px solid currentColor; font: 700 12px var(--mono); font-style: normal; }
.tag-summary em[data-active="true"] { color: var(--green); }
.source-columns { display: grid; grid-template-columns: 1fr 1fr; }
.source-columns article { padding: 16px; min-width: 0; }
.source-columns article + article { border-left: 1px solid var(--line); }
.source-columns h3 { margin: 0 0 10px; color: var(--dim); font: 700 12px var(--mono); }
.source-columns ul { margin: 0; padding: 0; display: flex; flex-wrap: wrap; gap: 7px; list-style: none; }
.source-columns li { padding: 5px 8px; overflow-wrap: anywhere; border: 1px solid var(--line-strong); font: 13px var(--mono); }
.source-columns li.empty { color: var(--dim); border-style: dashed; }
.decision-state { margin: 18px 0 0; display: grid; grid-template-columns: repeat(3, 1fr); border: 1px solid var(--line); }
.decision-state div { min-width: 0; padding: 12px 14px; border-right: 1px solid var(--line); border-bottom: 1px solid var(--line); }
.decision-state div:nth-child(3n) { border-right: 0; }
.decision-state div:nth-last-child(-n+3) { border-bottom: 0; }
.decision-state dt { color: var(--dim); font: 700 11px var(--mono); letter-spacing: .08em; }
.decision-state dd { margin: 4px 0 0; overflow-wrap: anywhere; font-weight: 700; font-size: 14px; }
.trace { margin-top: 18px; padding: 16px; border-top: 1px solid var(--line); background: #0b1011; }
.trace > span { color: var(--dim); font: 700 11px var(--mono); letter-spacing: .1em; }
.trace ol { margin: 10px 0 0; padding: 0; display: flex; flex-wrap: wrap; gap: 7px; list-style: none; }
.trace li { padding: 5px 8px; color: var(--muted); border: 1px solid var(--line); font: 12px var(--mono); }
.trace li:last-child { color: var(--ink); border-color: var(--cyan); }

.code-head strong { padding: 5px 8px; color: var(--amber); border: 1px solid var(--line-strong); font: 700 12px var(--mono); }
.code-lines { margin: 24px 0 0; padding: 16px 0 16px 48px; overflow: auto; border: 1px solid var(--line); background: #070b0c; font: 13px/1.75 var(--mono); }
.code-lines li { padding: 0 14px; color: #a0aaa7; white-space: pre; }
.code-lines li::marker { color: #4d5956; }
.code-lines li.is-active { color: var(--ink); background: rgba(243,184,91,.13); box-shadow: inset 3px 0 var(--amber); }
.code-note { color: var(--dim); font-size: 13px; }

.controls { padding: 18px 22px; display: grid; grid-template-columns: 1fr auto; align-items: center; gap: 14px 24px; border-top: 1px solid var(--line); }
.progress-wrap { display: flex; align-items: center; flex-wrap: wrap; gap: 14px; }
.step-dots { display: flex; gap: 8px; }
.step-dots button { width: 11px; height: 11px; padding: 0; border: 0; border-radius: 50%; background: #46514f; cursor: pointer; }
.step-dots button.is-past { background: var(--cyan); }
.step-dots button.is-active { background: var(--amber); box-shadow: 0 0 0 4px rgba(243,184,91,.16); }
.progress-wrap label, #speed-message { color: var(--muted); font-size: 14px; }
.progress-wrap select { padding: 6px 8px; color: var(--ink); border: 1px solid var(--line-strong); background: #0b1011; }
.control-buttons { display: flex; flex-wrap: wrap; justify-content: flex-end; gap: 9px; }
.control-buttons button { min-height: 43px; padding: 8px 15px; color: var(--ink); border: 1px solid var(--line-strong); background: #12191a; cursor: pointer; }
.control-buttons button:hover:not(:disabled) { border-color: var(--amber); }
.control-buttons button:disabled { color: #596461; cursor: not-allowed; }
.control-buttons .next-button { color: var(--base); border-color: var(--amber); background: var(--amber); font-weight: 800; }
.control-buttons .is-playing { color: var(--base); border-color: var(--cyan); background: var(--cyan); }
.keyboard-help { grid-column: 1 / -1; margin: 0; color: var(--dim); font-size: 13px; }

.boundaries { margin-top: 64px; border-top: 1px solid var(--line); border-bottom: 1px solid var(--line); }
.boundary-grid article:first-child, .boundary-grid article:nth-child(2) { border-top: 3px solid var(--violet); }
.boundary-grid article:last-child { border-top: 3px solid var(--cyan); }
.decision-matrix { padding-bottom: 100px; }
.matrix-wrap { overflow-x: auto; border: 1px solid var(--line); }
table { width: 100%; min-width: 720px; border-collapse: collapse; background: var(--surface); }
th, td { padding: 18px 20px; text-align: left; border-right: 1px solid var(--line); border-bottom: 1px solid var(--line); }
th:last-child, td:last-child { border-right: 0; }
tbody tr:last-child th, tbody tr:last-child td { border-bottom: 0; }
thead th { color: var(--dim); font: 700 12px var(--mono); letter-spacing: .08em; }
tbody th { color: var(--cyan); font: 700 14px var(--mono); }
.accent-row { background: #1e1911; }
.accent-row th, .accent-row td { color: var(--amber); }
.sr-only { position: absolute; width: 1px; height: 1px; padding: 0; margin: -1px; overflow: hidden; clip: rect(0,0,0,0); white-space: nowrap; border: 0; }

@media (max-width: 1240px) {
  .lab-grid { grid-template-columns: 1fr 1.4fr; }
  .code-panel { grid-column: 1 / -1; border-top: 1px solid var(--line); }
  .state-panel { border-right: 0; }
  .scenario-tabs { grid-template-columns: repeat(6, minmax(150px, 1fr)); }
}
@media (max-width: 860px) {
  body { font-size: 16px; }
  .site-header { position: static; align-items: flex-start; padding-top: 16px; padding-bottom: 16px; }
  nav { flex-wrap: wrap; justify-content: flex-end; gap: 10px 18px; }
  .hero { grid-template-columns: 1fr; min-height: 0; gap: 36px; }
  .model-grid, .boundary-grid { grid-template-columns: 1fr; }
  .section-heading { align-items: start; flex-direction: column; gap: 14px; }
  .lab-toolbar { grid-template-columns: 1fr; }
  .step-readout { display: flex; justify-content: space-between; text-align: left; border-top: 1px solid var(--line); }
  .route-strip { grid-template-columns: 1fr 1fr; }
  .route-node:nth-child(2) { border-right: 0; }
  .route-node:nth-child(-n+2) { border-bottom: 1px solid var(--line); }
  .lab-grid { grid-template-columns: 1fr; }
  .explain-panel, .state-panel { border-right: 0; border-bottom: 1px solid var(--line); }
  .controls { grid-template-columns: 1fr; }
  .control-buttons { justify-content: flex-start; }
}
@media (max-width: 560px) {
  .site-header { display: block; }
  nav { margin-top: 14px; justify-content: flex-start; }
  .brand span:last-child { font-size: 12px; }
  .hero h1 { font-size: 46px; }
  .ledger-board { grid-template-columns: 1fr; }
  .tag-summary { border-right: 0; border-bottom: 1px solid var(--line); }
  .source-columns, .decision-state { grid-template-columns: 1fr; }
  .source-columns article + article { border-left: 0; border-top: 1px solid var(--line); }
  .decision-state div, .decision-state div:nth-child(3n) { border-right: 0; border-bottom: 1px solid var(--line); }
  .decision-state div:last-child { border-bottom: 0; }
  .route-strip { grid-template-columns: 1fr; }
  .route-node { border-right: 0; border-bottom: 1px solid var(--line); }
  .control-buttons button { flex: 1 1 44%; }
}

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
}