:root {
  --ink: #1d211e;
  --muted: #555b56;
  --soft: #7a807b;
  --accent: #76b900;
  --accent-ink: #3f6f00;
  --accent-tint: #f1f7e6;
  --line: #e5e8e2;
  --surface: #f6f7f4;
  --code-bg: #f3f4f1;
  --text: 760px;
  --wide: 1040px;
  --radius: 10px;
  --sans: "DM Sans", system-ui, -apple-system, "Segoe UI", Roboto, Arial, sans-serif;
  --mono: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
}

*,
*::before,
*::after { box-sizing: border-box; }

html { scroll-behavior: smooth; scroll-padding-top: 64px; }
@media (prefers-reduced-motion: reduce) { html { scroll-behavior: auto; } }

body {
  margin: 0;
  font-family: var(--sans);
  font-size: 17px;
  line-height: 1.65;
  color: var(--ink);
  background: #fff;
  -webkit-font-smoothing: antialiased;
}

a { color: var(--accent-ink); text-decoration-thickness: 1px; text-underline-offset: 2px; }
a:hover { color: var(--ink); }

img, video { display: block; max-width: 100%; height: auto; }

.skip-link {
  position: absolute; left: -9999px; top: 8px;
  background: var(--ink); color: #fff; padding: 8px 12px; border-radius: 6px; z-index: 100;
}
.skip-link:focus { left: 8px; }

/* Layout */
.wrap { max-width: var(--wide); margin: 0 auto; padding: 0 24px; }
.prose { max-width: var(--text); margin-left: auto; margin-right: auto; }
.prose p { margin: 0 0 1.1em; }

/* Header */
.header { border-top: 5px solid var(--accent); padding: 56px 0 32px; text-align: center; }
.kicker {
  margin: 0 0 14px; font-size: 13px; font-weight: 600; letter-spacing: 0.08em;
  text-transform: uppercase; color: var(--accent-ink);
}
h1 { margin: 0; font-weight: 700; line-height: 1.15; }
h1 .name { display: block; font-size: clamp(44px, 7vw, 64px); letter-spacing: -0.02em; }
h1 .subtitle {
  display: block; margin: 10px auto 0; max-width: 820px;
  font-size: clamp(20px, 2.6vw, 27px); font-weight: 500; color: var(--muted);
}
.authors { margin: 22px 0 2px; font-size: 18px; font-weight: 500; }
.meta { margin: 0; color: var(--soft); font-size: 15px; }

.links { display: flex; flex-wrap: wrap; justify-content: center; gap: 10px; margin-top: 22px; }
.button {
  display: inline-flex; align-items: center; gap: 6px;
  padding: 8px 18px; border-radius: 999px;
  background: var(--ink); color: #fff; text-decoration: none; font-weight: 500; font-size: 15px;
}
.button:hover { background: var(--accent-ink); color: #fff; }
.button.is-soon { background: var(--surface); color: var(--soft); border: 1px solid var(--line); cursor: default; }
.button.is-soon:hover { background: var(--surface); color: var(--soft); }
.button small { font-size: 12px; opacity: 0.85; }

/* Media */
.media { margin: 28px auto 36px; }
.media.text-width { max-width: var(--text); }
.frame {
  position: relative; overflow: hidden; border-radius: var(--radius);
  background: #111; aspect-ratio: 16 / 9;
}
.frame video { width: 100%; height: 100%; object-fit: cover; }
.frame[data-placeholder]::after {
  content: "Placeholder video"; position: absolute; top: 12px; left: 12px;
  padding: 3px 10px; border-radius: 999px; font-size: 12px; font-weight: 600;
  background: rgba(255, 255, 255, 0.9); color: var(--ink); pointer-events: none;
}
.frame .frame-label {
  position: absolute; left: 0; right: 0; bottom: 0; padding: 28px 16px 12px;
  color: #fff; font-weight: 500; font-size: 15px;
  background: linear-gradient(transparent, rgba(0, 0, 0, 0.55)); pointer-events: none;
}
.figure-img { border-radius: var(--radius); border: 1px solid var(--line); background: #fff; padding: 14px; }
.media.narrow { max-width: 560px; }
figcaption { margin-top: 10px; font-size: 14.5px; line-height: 1.55; color: var(--muted); }
.media.narrow figcaption { max-width: 560px; }
.media.text-width figcaption, .media figcaption { max-width: var(--text); margin-left: auto; margin-right: auto; }

/* Chapter navigation */
.chapter-nav {
  position: sticky; top: 0; z-index: 20;
  background: rgba(255, 255, 255, 0.92); backdrop-filter: blur(8px);
  border-top: 1px solid var(--line); border-bottom: 1px solid var(--line);
}
.chapter-nav ul {
  display: flex; gap: 4px; justify-content: center; flex-wrap: wrap;
  list-style: none; margin: 0 auto; padding: 8px 16px; max-width: var(--wide);
}
.chapter-nav a {
  display: block; padding: 5px 12px; border-radius: 999px;
  color: var(--muted); text-decoration: none; font-size: 14.5px; font-weight: 500;
}
.chapter-nav a:hover { color: var(--ink); background: var(--surface); }
.chapter-nav a.is-active { color: var(--accent-ink); background: var(--accent-tint); }

/* Chapters */
.chapter { padding: 64px 0 16px; border-top: 1px solid var(--line); }
.chapter:first-of-type { border-top: 0; }
.section-kicker {
  margin: 0 0 6px; font-size: 13px; font-weight: 600; letter-spacing: 0.08em;
  text-transform: uppercase; color: var(--accent-ink);
}
h2 { margin: 0 0 18px; font-size: clamp(28px, 3.4vw, 36px); line-height: 1.2; letter-spacing: -0.01em; }
h3 { margin: 40px 0 10px; font-size: 22px; line-height: 1.3; }
.lede { font-size: 19px; color: var(--ink); }

/* Tasks */
.task-grid { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 28px; margin: 28px 0 8px; }
.task h3 { margin: 16px 0 6px; }
.instruction {
  margin: 0 0 10px; padding: 10px 14px; border-left: 3px solid var(--accent);
  background: var(--surface); border-radius: 0 8px 8px 0; font-style: italic;
}
.task p { margin: 0 0 10px; }
.chips { display: flex; flex-wrap: wrap; gap: 6px; list-style: none; padding: 0; margin: 10px 0 0; }
.chips li {
  padding: 2px 10px; border-radius: 999px; font-size: 13px; font-weight: 500;
  background: var(--accent-tint); color: var(--accent-ink);
}

.sim-grid { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 16px; margin: 20px 0 8px; }
.sim-grid .frame { border-radius: 8px; }
.sim-grid .frame[data-placeholder]::after { top: 8px; left: 8px; font-size: 11px; }
.sim-grid .tag { display: inline-block; font-weight: 700; margin-right: 6px; }
.sim-grid.two { grid-template-columns: repeat(2, minmax(0, 1fr)); }

/* Steps */
.step { margin: 36px 0; }
.step h3 { margin-top: 0; }
.step-num { color: var(--accent-ink); }
pre.code {
  margin: 14px 0 18px; padding: 16px 18px; overflow-x: auto;
  background: var(--code-bg); border: 1px solid var(--line); border-radius: 8px;
  font-family: var(--mono); font-size: 13.5px; line-height: 1.6; color: var(--ink);
}
pre.code .c { color: var(--soft); }
pre.code .s { color: var(--accent-ink); }

/* Ladder */
.ladder { display: grid; grid-template-columns: repeat(4, minmax(0, 1fr)); gap: 14px; margin: 26px 0; padding: 0; list-style: none; }
.ladder li { padding: 16px; background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius); }
.ladder .status { display: block; font-size: 13px; font-weight: 700; letter-spacing: 0.06em; text-transform: uppercase; color: var(--accent-ink); }
.ladder .value { display: block; margin: 6px 0 8px; font-size: 15px; line-height: 1.5; }
.ladder .who { display: block; font-size: 13px; color: var(--soft); }

.chain {
  display: flex; flex-wrap: wrap; align-items: center; gap: 8px;
  margin: 18px 0 26px; padding: 14px; border: 1px dashed var(--line); border-radius: var(--radius);
  font-size: 14.5px;
}
.chain .state { padding: 5px 12px; border-radius: 8px; background: #fff; border: 1px solid var(--line); }
.chain .op { color: var(--soft); font-size: 13px; }
.chain .op::before { content: "\2192"; margin-right: 6px; color: var(--accent); }

/* Recovery */
.gap-grid { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 28px; margin: 28px 0 8px; }
.gap-kind { display: block; font-size: 13px; font-weight: 600; letter-spacing: 0.06em; text-transform: uppercase; color: var(--accent-ink); margin-top: 16px; }
.gap-grid h3 { margin: 2px 0 6px; }

/* Results table */
.table-wrap { max-width: var(--text); margin: 24px auto 8px; overflow-x: auto; }
table.results { width: 100%; border-collapse: collapse; font-size: 15.5px; }
table.results th, table.results td { padding: 10px 12px; text-align: left; border-bottom: 1px solid var(--line); }
table.results thead th { font-size: 13px; font-weight: 600; color: var(--muted); border-bottom: 2px solid var(--ink); }
table.results td.num, table.results th.num { text-align: right; font-variant-numeric: tabular-nums; }
table.results tr.ours td { font-weight: 700; background: var(--accent-tint); }
.table-caption { max-width: var(--text); margin: 0 auto 28px; font-size: 14.5px; color: var(--muted); }

/* FAQ */
.faq details { border-bottom: 1px solid var(--line); padding: 4px 0; }
.faq summary {
  cursor: pointer; list-style: none; padding: 12px 28px 12px 0; position: relative;
  font-weight: 600; font-size: 17px;
}
.faq summary::-webkit-details-marker { display: none; }
.faq summary::after { content: "+"; position: absolute; right: 4px; top: 10px; font-size: 20px; color: var(--soft); }
.faq details[open] summary::after { content: "\2212"; }
.faq details p { margin: 0 0 14px; color: var(--muted); }
.limits { padding-left: 20px; }
.limits li { margin-bottom: 10px; }

/* Citation */
.bibtex-block { position: relative; }
.bibtex-block pre.code { padding-right: 90px; }
.copy-button {
  position: absolute; top: 10px; right: 10px;
  padding: 5px 12px; border-radius: 6px; border: 1px solid var(--line);
  background: #fff; font: 500 13px var(--sans); color: var(--ink); cursor: pointer;
}
.copy-button:hover { border-color: var(--accent); }

footer { margin-top: 64px; padding: 28px 0 48px; border-top: 1px solid var(--line); color: var(--soft); font-size: 14px; text-align: center; }

/* Responsive */
@media (max-width: 860px) {
  .ladder { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .sim-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); }
}
@media (max-width: 680px) {
  body { font-size: 16px; }
  .task-grid, .gap-grid { grid-template-columns: minmax(0, 1fr); }
  .header { padding-top: 40px; }
  .chapter { padding-top: 48px; }
}
@media (max-width: 460px) {
  .ladder, .sim-grid, .sim-grid.two { grid-template-columns: minmax(0, 1fr); }
}

/* Real footage that is not 16:9: show it whole on a dark frame */
.frame.fit { background: #0f1512; }
.frame.fit video { object-fit: contain; }

/* Storyboard stepper (rolling example) */
.storyboard { margin: 8px 0 24px; }
.storyboard-controls { display: flex; align-items: center; gap: 10px; justify-content: center; flex-wrap: wrap; }
.sb-steps { display: flex; gap: 6px; list-style: none; margin: 0; padding: 0; flex-wrap: wrap; justify-content: center; }
.sb-steps button, .sb-prev, .sb-next {
  font: 500 14px var(--sans); border: 1px solid var(--line); background: #fff; color: var(--muted);
  padding: 6px 12px; border-radius: 999px; cursor: pointer;
}
.sb-steps button[aria-current="true"] { background: var(--ink); color: #fff; border-color: var(--ink); }
.sb-steps button:hover, .sb-prev:hover, .sb-next:hover { border-color: var(--accent); color: var(--ink); }
.sb-prev, .sb-next { font-size: 16px; padding: 5px 12px; }
.storyboard .sb-frame { margin-top: 14px; }

/* Method: the loop as six illustrated steps */
.step { margin: 8px 0 12px; }
.step .media { margin: 14px auto 40px; }
.step h3 { display: flex; align-items: center; gap: 12px; }
.step-num {
  display: inline-flex; align-items: center; justify-content: center; flex: none;
  width: 30px; height: 30px; border-radius: 50%;
  background: var(--ink); color: #fff; font-size: 15px; font-weight: 600;
}

/* Sandbox: write-channel cards and document viewer */
.sb-cards { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 16px; margin: 28px 0 24px; }
.sb-card { border: 1px solid var(--line); border-radius: var(--radius); padding: 18px 18px 16px; background: #fff; }
.sb-card h3 { display: flex; align-items: center; gap: 10px; margin: 0 0 8px; font-size: 17px; }
.sb-card p { margin: 0 0 12px; font-size: 15px; line-height: 1.55; color: var(--muted); }
.sb-num {
  display: inline-flex; align-items: center; justify-content: center; flex: none;
  width: 24px; height: 24px; border-radius: 50%; background: var(--accent); color: #fff; font-size: 13px; font-weight: 700;
}
.sb-chips { display: flex; flex-wrap: wrap; gap: 6px; }
.sb-chips button {
  font: 500 13px/1 var(--mono); padding: 6px 9px; border-radius: 999px; cursor: pointer;
  border: 1px solid var(--line); background: var(--surface); color: var(--ink);
}
.sb-chips button:hover, .sb-chips button:focus-visible { background: var(--accent-tint); border-color: var(--accent); color: var(--accent-ink); }

.sb-viewer {
  display: grid; grid-template-columns: 290px minmax(0, 1fr); height: 640px;
  border: 1px solid var(--line); border-radius: var(--radius); overflow: hidden; background: #fff;
  scroll-margin-top: 64px;
}
.sb-side { display: flex; flex-direction: column; min-height: 0; background: var(--surface); border-right: 1px solid var(--line); }
.sb-filter {
  margin: 12px; padding: 8px 10px; font: 14px var(--sans); color: var(--ink);
  border: 1px solid var(--line); border-radius: 8px; background: #fff;
}
.sb-filter:focus { outline: 2px solid var(--accent); outline-offset: 0; border-color: var(--accent); }
.sb-tree { overflow-y: auto; padding: 0 6px 12px; }
.sb-group { margin-bottom: 4px; }
.sb-group-head {
  display: flex; align-items: center; gap: 6px; width: 100%; padding: 8px 6px 4px; border: 0; background: none;
  font: 600 13px var(--sans); color: var(--ink); text-align: left; cursor: pointer; flex-wrap: wrap;
}
.sb-caret { width: 0; height: 0; border-left: 5px solid var(--soft); border-top: 4px solid transparent; border-bottom: 4px solid transparent; transition: transform 0.15s; }
.sb-group-head[aria-expanded="true"] .sb-caret { transform: rotate(90deg); }
.sb-group-label { white-space: pre; }
.sb-group-note { font-weight: 500; font-size: 11px; color: var(--soft); padding: 1px 6px; border: 1px solid var(--line); border-radius: 999px; background: #fff; }
.sb-group ul { list-style: none; margin: 0; padding: 0 0 0 14px; }
.sb-file {
  display: block; width: 100%; padding: 4px 8px; border: 0; border-radius: 6px; background: none; cursor: pointer;
  font: 13px/1.4 var(--mono); color: var(--muted); text-align: left; overflow: hidden; text-overflow: ellipsis; white-space: nowrap;
}
.sb-file:hover { background: #fff; color: var(--ink); }
.sb-file[aria-current="true"] { background: var(--accent-tint); color: var(--accent-ink); font-weight: 600; }

.sb-doc { overflow-y: auto; padding: 22px 28px 32px; min-width: 0; outline: none; }
.sb-doc-head { display: flex; align-items: center; justify-content: space-between; gap: 12px; flex-wrap: wrap; }
.sb-path { margin: 0; font: 600 14px var(--mono); color: var(--ink); word-break: break-all; }
.sb-role { font-size: 12px; font-weight: 600; padding: 3px 10px; border-radius: 999px; white-space: nowrap; }
.sb-role.is-overview { background: var(--surface); color: var(--muted); border: 1px solid var(--line); }
.sb-role.is-readonly { background: #eef1f6; color: #34507a; }
.sb-role.is-agent { background: var(--accent-tint); color: var(--accent-ink); }
.sb-role.is-reply { background: #f4f0e8; color: #6b5420; }
.sb-role.is-record { background: #f2eef6; color: #5a3d7a; }
.sb-summary { margin: 8px 0 16px; padding-bottom: 14px; border-bottom: 1px solid var(--line); font-size: 15px; color: var(--muted); }

.sb-body { font-size: 15px; line-height: 1.6; }
.sb-body.sb-md h1 { font-size: 22px; margin: 4px 0 12px; }
.sb-body.sb-md h2 { font-size: 18px; margin: 22px 0 8px; }
.sb-body.sb-md h3 { font-size: 16px; margin: 18px 0 6px; }
.sb-body.sb-md p, .sb-body.sb-md ul, .sb-body.sb-md ol { margin: 0 0 10px; }
.sb-body.sb-md ul, .sb-body.sb-md ol { padding-left: 22px; }
.sb-body.sb-md table { border-collapse: collapse; width: 100%; margin: 8px 0 14px; font-size: 13.5px; display: block; overflow-x: auto; }
.sb-body.sb-md th, .sb-body.sb-md td { border: 1px solid var(--line); padding: 5px 8px; vertical-align: top; text-align: left; }
.sb-body.sb-md th { background: var(--surface); }
.sb-body code { font-family: var(--mono); font-size: 0.88em; background: var(--code-bg); padding: 1px 4px; border-radius: 4px; }
.sb-body pre { margin: 8px 0 14px; padding: 12px 14px; overflow-x: auto; background: var(--code-bg); border: 1px solid var(--line); border-radius: 8px; }
.sb-body pre code { background: none; padding: 0; font-size: 12.5px; line-height: 1.55; }
.sb-body pre.sb-code { margin-top: 0; }
.sb-body pre.sb-py, .sb-body pre.sb-txt, .sb-body.sb-md pre { white-space: pre-wrap; overflow-wrap: anywhere; }
.sb-belief { color: #34507a; font-weight: 600; }
.sb-intent { color: #6b5420; font-weight: 600; }
.sb-achieved { color: var(--accent-ink); font-weight: 600; }
.sb-comment { color: var(--soft); }
.sb-img { display: block; max-width: 100%; border-radius: 8px; border: 1px solid var(--line); }
video.sb-img { width: 100%; height: auto; background: #f2f2f0; }
.sb-body .sb-tag { margin: 16px 0 4px; font-size: 13px; color: var(--muted); }
.sb-body .sb-tag strong { color: var(--ink); }
.sb-body .sb-tag + pre { margin-top: 0; }
.sb-body blockquote { margin: 0 0 10px; padding: 2px 12px; border-left: 3px solid var(--line); }
.sb-body .sb-view { max-width: 420px; margin: 2px 0 8px; }
.sb-body .sb-note { font-size: 13px; color: var(--muted); margin: 4px 0 10px; }
.sb-foot { max-width: var(--text); margin: 14px auto 0; font-size: 14px; color: var(--muted); }

@media (max-width: 860px) {
  .sb-cards { grid-template-columns: minmax(0, 1fr); }
  .sb-viewer { grid-template-columns: minmax(0, 1fr); grid-template-rows: 220px 520px; height: auto; }
  .sb-side { border-right: 0; border-bottom: 1px solid var(--line); }
  .sb-doc { padding: 18px; }
}