/* Magic Book of Algorithms - blueprint theme.
   Hand written, no framework, no external fonts. */

:root {
  --bg: #05070d;
  --panel: #0a0e17;
  --panel-2: #070a11;
  --ink: #c8d5e6;
  --ink-dim: #7c8ca4;
  --ink-faint: #4a586d;
  --accent: #3fe0ff;
  --accent-deep: #0e91b8;
  --wire: rgba(63, 224, 255, .18);
  --wire-strong: rgba(63, 224, 255, .42);
  --grid: rgba(125, 195, 235, .045);
  --mono: ui-monospace, "Cascadia Mono", Consolas, "DejaVu Sans Mono", monospace;
  --sans: "Segoe UI", system-ui, -apple-system, "Helvetica Neue", Arial, sans-serif;
  --shell: 1320px;
  --sidebar: 262px;
}

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

html { scroll-behavior: smooth; scroll-padding-top: 84px; }

body {
  margin: 0;
  min-height: 100vh;
  font-family: var(--sans);
  font-size: 16px;
  line-height: 1.6;
  color: var(--ink);
  background-color: var(--bg);
  background-image:
    linear-gradient(var(--grid) 1px, transparent 1px),
    linear-gradient(90deg, var(--grid) 1px, transparent 1px);
  background-size: 44px 44px;
  -webkit-font-smoothing: antialiased;
}

body::before {
  content: "";
  position: fixed;
  inset: 0;
  pointer-events: none;
  background:
    radial-gradient(70% 45% at 50% -10%, rgba(63, 224, 255, .10), transparent 70%),
    radial-gradient(50% 40% at 100% 100%, rgba(14, 145, 184, .07), transparent 70%);
  z-index: 0;
}

a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; }

h1, h2, h3, h4 { font-weight: 600; line-height: 1.25; margin: 0; }

::selection { background: var(--accent); color: #04070c; }

:focus-visible { outline: 2px solid var(--accent); outline-offset: 3px; }

.skip {
  position: absolute;
  left: -9999px;
  top: 0;
  padding: 10px 16px;
  background: var(--panel);
  border: 1px solid var(--wire-strong);
  z-index: 50;
}
.skip:focus { left: 12px; top: 12px; }

/* --- brand ------------------------------------------------------------- */

.brand { display: flex; align-items: center; gap: 12px; color: var(--ink); }
.brand:hover { text-decoration: none; }

.brand-mark {
  width: 15px;
  height: 15px;
  flex: none;
  border: 1.5px solid var(--accent);
  transform: rotate(45deg);
  position: relative;
  box-shadow: 0 0 14px rgba(63, 224, 255, .35);
}
.brand-mark::after {
  content: "";
  position: absolute;
  inset: 3px;
  background: var(--accent);
}

.brand-text { display: flex; flex-direction: column; line-height: 1.05; }
.brand-text b {
  font: 600 14px/1.1 var(--mono);
  letter-spacing: .16em;
  text-transform: uppercase;
}
.brand-text em {
  font: 400 10px/1.4 var(--mono);
  font-style: normal;
  letter-spacing: .26em;
  text-transform: uppercase;
  color: var(--ink-faint);
}

/* --- topbar ------------------------------------------------------------ */

.topbar {
  position: sticky;
  top: 0;
  z-index: 30;
  display: flex;
  align-items: center;
  gap: 20px;
  height: 62px;
  padding: 0 24px;
  border-bottom: 1px solid var(--wire);
  background: rgba(5, 7, 13, .82);
  backdrop-filter: blur(10px);
}

.menu {
  display: none;
  width: 34px;
  height: 30px;
  padding: 0;
  background: none;
  border: 1px solid var(--wire);
  color: var(--accent);
  cursor: pointer;
}
.menu span, .menu span::before, .menu span::after {
  display: block;
  width: 16px;
  height: 1px;
  margin: 0 auto;
  background: currentColor;
  position: relative;
}
.menu span::before { content: ""; position: absolute; top: -5px; }
.menu span::after { content: ""; position: absolute; top: 5px; }

.search { position: relative; margin-left: auto; width: min(340px, 42vw); }

.search input {
  width: 100%;
  height: 34px;
  padding: 0 34px 0 12px;
  font: 400 13px/1 var(--sans);
  color: var(--ink);
  background: var(--panel-2);
  border: 1px solid var(--wire);
  border-radius: 0;
  appearance: none;
}
.search input::placeholder { color: var(--ink-faint); }
.search input:focus { border-color: var(--wire-strong); outline: none; box-shadow: 0 0 0 1px var(--wire-strong); }

.search kbd {
  position: absolute;
  right: 9px;
  top: 8px;
  padding: 1px 6px;
  font: 400 11px/1.4 var(--mono);
  color: var(--ink-faint);
  border: 1px solid var(--wire);
  pointer-events: none;
}
.search input:focus ~ kbd { opacity: 0; }

.results {
  position: absolute;
  top: calc(100% + 6px);
  right: 0;
  width: min(420px, 82vw);
  max-height: 64vh;
  overflow-y: auto;
  padding: 4px;
  background: var(--panel);
  border: 1px solid var(--wire-strong);
  box-shadow: 0 24px 60px rgba(0, 0, 0, .6);
  z-index: 40;
}
.results a {
  display: block;
  padding: 9px 12px;
  color: var(--ink);
  border-left: 2px solid transparent;
}
.results a:hover, .results a.on {
  background: rgba(63, 224, 255, .08);
  border-left-color: var(--accent);
  text-decoration: none;
}
.results a b { display: block; font-weight: 600; font-size: 14px; }
.results a span {
  display: block;
  font: 400 11px/1.5 var(--mono);
  letter-spacing: .08em;
  text-transform: uppercase;
  color: var(--ink-faint);
}
.results p { margin: 0; padding: 12px; font-size: 13px; color: var(--ink-faint); }

.lang {
  font: 600 12px/1 var(--mono);
  letter-spacing: .12em;
  color: var(--ink-dim);
  border: 1px solid var(--wire);
  padding: 8px 10px;
}
.lang:hover { color: var(--accent); border-color: var(--wire-strong); text-decoration: none; }

/* --- shell and sidebar -------------------------------------------------- */

.shell {
  position: relative;
  z-index: 1;
  display: grid;
  grid-template-columns: var(--sidebar) minmax(0, 1fr);
  max-width: var(--shell);
  margin: 0 auto;
}

.sidebar {
  position: sticky;
  top: 62px;
  align-self: start;
  max-height: calc(100vh - 62px);
  overflow-y: auto;
  padding: 28px 22px 40px;
  border-right: 1px solid var(--wire);
}

.sidebar-title {
  margin: 0 0 16px;
  font: 600 10px/1 var(--mono);
  letter-spacing: .28em;
  text-transform: uppercase;
  color: var(--ink-faint);
}

.sidebar details { margin-bottom: 6px; }
.sidebar summary {
  display: flex;
  align-items: center;
  gap: 9px;
  padding: 6px 0;
  font-size: 13.5px;
  color: var(--ink);
  cursor: pointer;
  list-style: none;
}
.sidebar summary::-webkit-details-marker { display: none; }
.sidebar summary::after {
  content: "";
  width: 5px;
  height: 5px;
  margin-left: auto;
  border-right: 1px solid var(--ink-faint);
  border-bottom: 1px solid var(--ink-faint);
  transform: rotate(45deg);
  transition: transform .18s ease;
}
.sidebar details[open] summary::after { transform: rotate(-135deg); }
.sidebar summary:hover { color: var(--accent); }

.code {
  font: 600 9px/1 var(--mono);
  letter-spacing: .12em;
}
.sidebar summary .code {
  padding: 4px 5px;
  color: var(--accent-deep);
  border: 1px solid var(--wire);
}

.sidebar ul { margin: 2px 0 12px; padding: 0 0 0 12px; list-style: none; border-left: 1px solid var(--wire); }
.sidebar li a {
  display: block;
  padding: 5px 10px;
  font-size: 13.5px;
  color: var(--ink-dim);
  border-left: 2px solid transparent;
  margin-left: -13px;
  padding-left: 21px;
}
.sidebar li a:hover { color: var(--ink); text-decoration: none; }
.sidebar li a[aria-current] {
  color: var(--accent);
  border-left-color: var(--accent);
  background: linear-gradient(90deg, rgba(63, 224, 255, .09), transparent 70%);
}

main { padding: 44px 48px 90px; min-width: 0; }

/* --- footer ------------------------------------------------------------- */

.footer {
  position: relative;
  z-index: 1;
  max-width: var(--shell);
  margin: 0 auto;
  padding: 26px 48px 40px;
  border-top: 1px solid var(--wire);
  font-size: 12.5px;
  color: var(--ink-faint);
}
.footer p { margin: 0 0 4px; }
.footer .mark {
  font: 600 11px/1 var(--mono);
  letter-spacing: .22em;
  text-transform: uppercase;
  color: var(--ink-dim);
  margin-bottom: 10px;
}
.footer .privacy { color: var(--accent-deep); }

/* --- corner ticks ------------------------------------------------------- */

.card, .code, .figure, .facts, .demo { position: relative; }

.card::before, .card::after,
.code::before, .code::after,
.figure::before, .figure::after {
  content: "";
  position: absolute;
  width: 7px;
  height: 7px;
  border: 1px solid var(--wire-strong);
  pointer-events: none;
}
.card::before, .code::before, .figure::before {
  top: -1px; left: -1px; border-right: 0; border-bottom: 0;
}
.card::after, .code::after, .figure::after {
  bottom: -1px; right: -1px; border-left: 0; border-top: 0;
}

/* --- hero and index ----------------------------------------------------- */

.hero { max-width: 760px; margin-bottom: 62px; }

.eyeline {
  margin: 0 0 18px;
  font: 600 10px/1 var(--mono);
  letter-spacing: .3em;
  text-transform: uppercase;
  color: var(--accent-deep);
}
.eyeline::before {
  content: "";
  display: inline-block;
  width: 26px;
  height: 1px;
  margin-right: 12px;
  vertical-align: middle;
  background: var(--wire-strong);
}

.hero h1 {
  font-size: clamp(34px, 5.4vw, 54px);
  letter-spacing: -.02em;
  margin-bottom: 18px;
}
.hero h1::after {
  content: "";
  display: block;
  width: 72px;
  height: 2px;
  margin-top: 20px;
  background: linear-gradient(90deg, var(--accent), transparent);
}

.lede { margin: 0; font-size: 17px; color: var(--ink-dim); max-width: 62ch; }

.stats { display: flex; flex-wrap: wrap; gap: 34px; margin: 34px 0 0; }
.stats div { display: flex; flex-direction: column-reverse; gap: 4px; }
.stats dt {
  font: 400 10px/1 var(--mono);
  letter-spacing: .22em;
  text-transform: uppercase;
  color: var(--ink-faint);
}
.stats dd { margin: 0; font: 600 22px/1 var(--mono); color: var(--accent); }

.group { margin-bottom: 58px; }

.group-head {
  display: grid;
  grid-template-columns: auto 1fr;
  gap: 4px 14px;
  align-items: center;
  padding-bottom: 14px;
  margin-bottom: 22px;
  border-bottom: 1px solid var(--wire);
}
.group-head .code {
  grid-row: span 2;
  align-self: start;
  padding: 7px 8px;
  font-size: 10px;
  color: var(--accent);
  border: 1px solid var(--wire-strong);
}
.group-head h2 { font-size: 19px; letter-spacing: .01em; }
.group-head p { margin: 0; font-size: 13.5px; color: var(--ink-faint); }

.cards { display: grid; grid-template-columns: repeat(auto-fill, minmax(252px, 1fr)); gap: 14px; }

.card {
  display: flex;
  flex-direction: column;
  gap: 8px;
  padding: 18px 18px 16px;
  color: var(--ink);
  background: linear-gradient(160deg, var(--panel), var(--panel-2));
  border: 1px solid var(--wire);
  transition: border-color .18s ease, transform .18s ease, background .18s ease;
}
.card:hover {
  border-color: var(--wire-strong);
  transform: translateY(-3px);
  text-decoration: none;
  background: linear-gradient(160deg, #0d1420, var(--panel-2));
}
.card .num {
  font: 600 10px/1 var(--mono);
  letter-spacing: .18em;
  color: var(--ink-faint);
}
.card:hover .num { color: var(--accent); }
.card h3 { font-size: 16.5px; }
.card p { margin: 0; font-size: 13.5px; color: var(--ink-dim); flex: 1; }
.card .meta {
  align-self: flex-start;
  padding: 3px 7px;
  font: 600 11px/1.4 var(--mono);
  color: var(--accent-deep);
  border: 1px solid var(--wire);
}

/* --- algorithm page ----------------------------------------------------- */

.algorithm { max-width: 900px; }

.page-head { margin-bottom: 26px; }

.crumb {
  display: flex;
  align-items: center;
  gap: 12px;
  margin: 0 0 14px;
  font: 600 10px/1 var(--mono);
  letter-spacing: .22em;
  text-transform: uppercase;
}
.crumb a { color: var(--ink-faint); }
.crumb a:hover { color: var(--accent); }
.crumb span { color: var(--accent-deep); }
.crumb span::before {
  content: "";
  display: inline-block;
  width: 20px;
  height: 1px;
  margin-right: 12px;
  vertical-align: middle;
  background: var(--wire);
}

.page-head h1 { font-size: clamp(28px, 4vw, 40px); letter-spacing: -.015em; margin-bottom: 12px; }

.facts {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
  gap: 1px;
  margin: 30px 0 40px;
  background: var(--wire);
  border: 1px solid var(--wire);
}
.facts div { padding: 14px 16px; background: var(--panel-2); }
.facts dt {
  font: 400 10px/1 var(--mono);
  letter-spacing: .18em;
  text-transform: uppercase;
  color: var(--ink-faint);
  margin-bottom: 8px;
}
.facts dd { margin: 0; font: 600 15px/1.3 var(--mono); color: var(--accent); }

h2.section {
  display: flex;
  align-items: center;
  gap: 14px;
  margin: 52px 0 20px;
  font: 600 11px/1 var(--mono);
  letter-spacing: .26em;
  text-transform: uppercase;
  color: var(--ink-dim);
}
h2.section span { color: var(--accent); }
h2.section::after {
  content: "";
  flex: 1;
  height: 1px;
  background: linear-gradient(90deg, var(--wire), transparent);
}

/* --- prose -------------------------------------------------------------- */

.prose { max-width: 68ch; }
.prose p { margin: 0 0 16px; }
.prose h3 {
  margin: 30px 0 12px;
  font-size: 16px;
  color: var(--ink);
}
.prose h4 { margin: 22px 0 8px; font-size: 14px; color: var(--ink-dim); }
.prose strong { color: #eaf4ff; font-weight: 600; }
.prose em { color: var(--ink); font-style: italic; }

.prose ul, .prose ol { margin: 0 0 16px; padding-left: 22px; }
.prose li { margin-bottom: 7px; }
.prose ul { list-style: none; padding-left: 18px; }
.prose ul li { position: relative; }
.prose ul li::before {
  content: "";
  position: absolute;
  left: -16px;
  top: .62em;
  width: 5px;
  height: 5px;
  border: 1px solid var(--accent);
}
.prose ol { list-style: none; counter-reset: step; padding-left: 0; }
.prose ol li { counter-increment: step; padding-left: 34px; position: relative; }
.prose ol li::before {
  content: counter(step, decimal-leading-zero);
  position: absolute;
  left: 0;
  top: .1em;
  font: 600 11px/1.7 var(--mono);
  color: var(--accent-deep);
}

.prose code, .facts code {
  padding: 1px 5px;
  font: 400 13px/1.5 var(--mono);
  color: #9fe9ff;
  background: rgba(63, 224, 255, .07);
  border: 1px solid var(--wire);
}

.prose .note {
  padding: 12px 16px;
  margin: 22px 0;
  color: var(--ink-dim);
  background: rgba(63, 224, 255, .04);
  border-left: 2px solid var(--accent-deep);
}

.related { margin-top: 54px; padding-top: 20px; border-top: 1px solid var(--wire); }
.related p {
  margin: 0 0 12px;
  font: 600 10px/1 var(--mono);
  letter-spacing: .26em;
  text-transform: uppercase;
  color: var(--ink-faint);
}
.related ul { display: flex; flex-wrap: wrap; gap: 10px; margin: 0; padding: 0; list-style: none; }
.related a {
  display: block;
  padding: 7px 13px;
  font-size: 13.5px;
  color: var(--ink);
  border: 1px solid var(--wire);
}
.related a:hover { color: var(--accent); border-color: var(--wire-strong); text-decoration: none; }

.button {
  display: inline-block;
  margin-top: 18px;
  padding: 10px 18px;
  font: 600 12px/1 var(--mono);
  letter-spacing: .16em;
  text-transform: uppercase;
  color: var(--accent);
  border: 1px solid var(--wire-strong);
}
.button:hover { background: rgba(63, 224, 255, .08); text-decoration: none; }

/* --- code --------------------------------------------------------------- */

.code { margin: 0 0 8px; background: var(--panel-2); border: 1px solid var(--wire); }

.code-head {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 9px 14px;
  border-bottom: 1px solid var(--wire);
  background: rgba(63, 224, 255, .025);
}
.code-head .file {
  font: 400 11px/1.4 var(--mono);
  letter-spacing: .04em;
  color: var(--ink-faint);
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}
.code-head .tag {
  margin-left: auto;
  padding: 2px 6px;
  font: 600 10px/1.4 var(--mono);
  letter-spacing: .12em;
  color: var(--accent);
  border: 1px solid var(--wire);
}

.code pre {
  margin: 0;
  padding: 18px 18px 20px;
  overflow-x: auto;
  font: 400 13.5px/1.7 var(--mono);
  tab-size: 4;
}
.code code { font: inherit; color: var(--ink); }

.code .cm { color: #4d6a80; font-style: italic; }
.code .kw { color: #59c2ff; }
.code .ty { color: #7fe3c8; }
.code .fn { color: #c4b5ff; }
.code .st { color: #ffc978; }
.code .nu { color: #ff9f7d; }
.code .id { color: var(--ink); }

.code.output { margin-bottom: 0; }
.code.output pre { color: #86d9c0; font-size: 12.5px; line-height: 1.5; }
.code.output .code-head { background: none; }

/* --- figures and demos --------------------------------------------------- */

.figure { margin: 28px 0 0; padding: 0; border: 1px solid var(--wire); background: var(--panel-2); }
.figure figcaption {
  padding: 10px 16px;
  border-top: 1px solid var(--wire);
  font-size: 12.5px;
  color: var(--ink-faint);
}

.viz {
  position: relative;
  display: grid;
  place-items: center;
  min-height: 190px;
  padding: 26px 18px;
  overflow: hidden;
}

.demo { border: 1px solid var(--wire); background: var(--panel-2); }
.demo canvas {
  display: block;
  width: 100%;
  height: auto;
  border-bottom: 1px solid var(--wire);
}

/* the noise field is drawn small on purpose, so keep the pixels crisp */
.demo-perlin canvas { image-rendering: pixelated; }

/* small pictures blown up: the grain and the cells have to stay crisp */
.demo-worley canvas, .demo-reaction canvas, .demo-edges canvas { image-rendering: pixelated; }
.demo-worley { display: grid; justify-items: center; }
.demo-worley canvas { width: min(100%, 400px); }
.demo-worley .demo-bar { width: 100%; }

/* the dithered picture is drawn small and blown up, so keep the grain crisp */
.demo-dither { display: grid; justify-items: center; }
.demo-dither canvas { width: min(100%, 400px); image-rendering: pixelated; }
.demo-dither .demo-bar { width: 100%; }

.demo-stipple { display: grid; justify-items: center; }
.demo-stipple canvas { width: min(100%, 420px); border: 0; border-bottom: 1px solid var(--wire); }
.demo-stipple .demo-bar { width: 100%; }
.demo-bar { display: flex; align-items: center; gap: 14px; padding: 10px 14px; }
.demo-bar button {
  padding: 7px 14px;
  font: 600 11px/1 var(--mono);
  letter-spacing: .14em;
  text-transform: uppercase;
  color: var(--accent);
  background: none;
  border: 1px solid var(--wire-strong);
  cursor: pointer;
}
.demo-bar button:hover { background: rgba(63, 224, 255, .08); }
.demo-bar output { font: 400 11px/1.4 var(--mono); color: var(--ink-faint); }

/* --- splash (language chooser) ------------------------------------------ */

.splash { display: grid; place-items: center; min-height: 100vh; }
.splash-box { display: grid; justify-items: center; gap: 18px; text-align: center; }
.splash .brand-text { align-items: center; }
.splash .choose { display: flex; gap: 12px; margin: 12px 0 0; }
.splash .choose a {
  padding: 9px 18px;
  font: 600 11px/1 var(--mono);
  letter-spacing: .18em;
  text-transform: uppercase;
  border: 1px solid var(--wire);
}
.splash .choose a:hover { border-color: var(--wire-strong); text-decoration: none; }

/* --- visualisation: two pictures side by side ----------------------------- */

.viz-compare {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 20px;
  place-items: start stretch;
  width: 100%;
}
.viz-compare figure { margin: 0; display: grid; gap: 8px; }
.viz-grid { gap: 14px 16px; }
.viz-compare img {
  display: block;
  width: 100%;
  height: auto;
  border: 1px solid var(--wire);
  background: #fff;
}
.viz-compare figcaption {
  font: 600 10px/1 var(--mono);
  letter-spacing: .22em;
  text-transform: uppercase;
  color: var(--ink-faint);
}

/* --- visualisation: pathfinding ------------------------------------------ */

.viz-path {
  display: grid;
  gap: 1px;
  width: 100%;
  /* the squares are empty, so they have to be stretched instead of centred */
  place-items: stretch;
}
.viz-path i { aspect-ratio: 1; background: rgba(214, 228, 240, .04); }
.viz-path i.sand { background: rgba(255, 205, 130, .12); }
.viz-path i.mud { background: rgba(150, 110, 70, .26); }
.viz-path i.wall { background: var(--wire-strong); }

/* the squares the search had to look at, in the order it looked at them */
.viz-path i.seen {
  animation: path-seen .01s linear both;
  animation-delay: calc(var(--o) * 4ms);
}
@keyframes path-seen {
  to { box-shadow: inset 0 0 0 99px rgba(63, 224, 255, .16); }
}

/* the way itself, drawn once the search has finished */
.viz-path i.path {
  animation: path-found .01s linear both;
  animation-delay: calc(var(--wait) + var(--p) * 14ms);
}
@keyframes path-found {
  to { box-shadow: inset 0 0 0 99px rgba(63, 224, 255, .72); }
}

.viz-path i.start, .viz-path i.goal { background: #d8ecff; animation: none; box-shadow: none; }

/* --- visualisation: benford ---------------------------------------------- */

.viz-benford {
  display: grid;
  grid-template-columns: repeat(9, 1fr);
  justify-items: stretch;
  align-items: end;
  gap: 10px;
  width: 100%;
  height: 150px;
}
.viz-benford .bar { display: grid; justify-items: center; gap: 6px; height: 100%; align-content: end; }
.viz-benford i {
  width: 100%;
  height: var(--h);
  background: linear-gradient(180deg, rgba(63, 224, 255, .55), rgba(63, 224, 255, .06));
  border: 1px solid var(--wire-strong);
  border-bottom: none;
  transform-origin: bottom;
  animation: benford-grow .9s cubic-bezier(.2, .7, .3, 1) both;
  animation-delay: calc(var(--i) * .07s);
}
.viz-benford b { font: 600 12px/1 var(--mono); color: var(--accent); }
.viz-benford span { font: 400 10px/1 var(--mono); color: var(--ink-faint); }

@keyframes benford-grow { from { transform: scaleY(0); } to { transform: scaleY(1); } }

/* --- visualisation: bubble sort ------------------------------------------ */

.viz-bubble { --bar: 26px; --bar-gap: 10px; }
.viz-bubble .bars { position: relative; display: flex; align-items: flex-end; gap: var(--bar-gap); height: 120px; }
.viz-bubble i {
  width: var(--bar);
  height: var(--h);
  background: linear-gradient(180deg, rgba(63, 224, 255, .55), rgba(63, 224, 255, .04));
  border: 1px solid var(--wire-strong);
  border-bottom: none;
}
.viz-bubble i:nth-child(3) { animation: swap-right 7s infinite; }
.viz-bubble i:nth-child(4) { animation: swap-left 7s infinite; }
.viz-bubble .scan {
  position: absolute;
  left: 50%;
  margin-left: calc((8 * var(--bar) + 7 * var(--bar-gap)) / -2 - 2px);
  top: 50%;
  width: calc(2 * var(--bar) + var(--bar-gap) + 4px);
  height: 138px;
  margin-top: -69px;
  border: 1px solid var(--accent);
  box-shadow: 0 0 22px rgba(63, 224, 255, .25) inset;
  animation: scan 7s steps(6, end) infinite;
}

@keyframes swap-right {
  0%, 30% { transform: translateX(0); }
  38%, 96% { transform: translateX(calc(var(--bar) + var(--bar-gap))); }
  100% { transform: translateX(0); }
}
@keyframes swap-left {
  0%, 30% { transform: translateX(0); }
  38%, 96% { transform: translateX(calc(-1 * (var(--bar) + var(--bar-gap)))); }
  100% { transform: translateX(0); }
}
@keyframes scan {
  from { transform: translateX(0); }
  to { transform: translateX(calc(6 * (var(--bar) + var(--bar-gap)))); }
}

/* --- visualisation: merge sort ------------------------------------------- */

.viz-merge {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 14px 26px;
  justify-items: center;
  align-items: center;
}
.viz-merge .row { display: flex; gap: 5px; opacity: .26; animation: merge-step 8s infinite; }
.viz-merge .r0 { grid-column: 1 / 3; }
.viz-merge .r1 { grid-column: 1; animation-delay: 2s; }
.viz-merge .r2 { grid-column: 2; animation-delay: 2s; }
.viz-merge .r3 { grid-column: 1 / 3; animation-delay: 4.4s; }
.viz-merge span {
  min-width: 32px;
  padding: 6px 7px;
  font: 600 12px/1 var(--mono);
  text-align: center;
  color: var(--ink);
  border: 1px solid var(--wire);
}
.viz-merge .r3 span { color: var(--accent); border-color: var(--wire-strong); }

@keyframes merge-step {
  0%, 1% { opacity: .26; transform: translateY(5px); }
  5%, 26% { opacity: 1; transform: none; }
  34%, 100% { opacity: .3; transform: none; }
}

/* --- visualisation: quick sort partition --------------------------------- */

.viz-partition { --cell: 40px; --cell-gap: 6px; }
.viz-partition .row { display: flex; gap: var(--cell-gap); }
.viz-partition span {
  width: var(--cell);
  padding: 9px 0;
  font: 600 13px/1 var(--mono);
  text-align: center;
  border: 1px solid var(--wire);
  color: var(--ink-dim);
}
.viz-partition .less {
  animation: fill 6s infinite;
  animation-delay: calc(var(--i) * .45s);
}
.viz-partition .greater { animation: dim 6s infinite; animation-delay: calc(var(--i) * .45s); }
.viz-partition .pivot { color: var(--accent); border-color: var(--accent); animation: pivot 6s infinite; }
.viz-partition .marker {
  position: absolute;
  bottom: 46px;
  left: calc(50% - (7 * var(--cell) + 6 * var(--cell-gap)) / 2);
  height: 2px;
  width: 0;
  background: linear-gradient(90deg, var(--accent), rgba(63, 224, 255, .15));
  animation: boundary 6s infinite;
}

@keyframes fill {
  0%, 8% { color: var(--ink-dim); background: none; border-color: var(--wire); }
  18%, 88% { color: #04070c; background: var(--accent); border-color: var(--accent); }
  100% { color: var(--ink-dim); background: none; border-color: var(--wire); }
}
@keyframes dim {
  0%, 8% { opacity: 1; }
  18%, 88% { opacity: .35; }
  100% { opacity: 1; }
}
@keyframes pivot {
  0%, 70% { box-shadow: none; }
  80%, 94% { box-shadow: 0 0 18px rgba(63, 224, 255, .5); }
  100% { box-shadow: none; }
}
@keyframes boundary {
  0%, 8% { width: 0; }
  85%, 94% { width: calc(4 * (var(--cell) + var(--cell-gap))); }
  100% { width: 0; }
}

/* --- visualisation: binary search ---------------------------------------- */

.viz-search { --cell: 40px; --cell-gap: 6px; --step: calc(var(--cell) + var(--cell-gap)); }
.viz-search .row { display: flex; gap: var(--cell-gap); }
.viz-search span {
  width: var(--cell);
  padding: 10px 0;
  font: 600 12px/1 var(--mono);
  text-align: center;
  color: var(--ink-dim);
  border: 1px solid var(--wire);
}
.viz-search .target { animation: found 6s infinite; }
.viz-search .window {
  position: absolute;
  top: 50%;
  left: calc(50% - (10 * var(--cell) + 9 * var(--cell-gap)) / 2);
  height: 54px;
  margin-top: -27px;
  border: 1px solid var(--accent);
  box-shadow: 0 0 26px rgba(63, 224, 255, .2) inset;
  animation: window 6s infinite;
}

@keyframes window {
  0%, 18% { transform: translateX(0); width: calc(10 * var(--cell) + 9 * var(--cell-gap)); }
  24%, 42% { transform: translateX(calc(5 * var(--step))); width: calc(5 * var(--cell) + 4 * var(--cell-gap)); }
  48%, 66% { transform: translateX(calc(5 * var(--step))); width: calc(2 * var(--cell) + var(--cell-gap)); }
  72%, 100% { transform: translateX(calc(5 * var(--step))); width: var(--cell); }
}
@keyframes found {
  0%, 70% { color: var(--ink-dim); border-color: var(--wire); }
  80%, 96% { color: #04070c; background: var(--accent); border-color: var(--accent); }
  100% { color: var(--ink-dim); border-color: var(--wire); background: none; }
}

/* --- visualisation: fibonacci -------------------------------------------- */

.viz-fib {
  display: grid;
  grid-template-columns: repeat(13, 1fr);
  grid-template-rows: repeat(8, 1fr);
  width: min(430px, 100%);
  aspect-ratio: 13 / 8;
  place-items: stretch;
}
.viz-fib span {
  grid-row: var(--r) / span var(--s);
  grid-column: var(--c) / span var(--s);
  display: grid;
  place-items: center;
  font: 600 11px/1 var(--mono);
  color: var(--accent);
  border: 1px solid var(--wire-strong);
  background: rgba(63, 224, 255, .03);
  animation: pop 6s infinite;
  animation-delay: calc(var(--i) * .32s);
}

@keyframes pop {
  0%, 3% { opacity: 0; transform: scale(.72); }
  9%, 86% { opacity: 1; transform: none; }
  100% { opacity: .12; transform: none; }
}

/* --- visualisation: bit rotation ----------------------------------------- */

.viz-rotate { padding-left: 0; padding-right: 0; }
.viz-rotate .strip {
  display: flex;
  width: max-content;
  animation: rotate 9s linear infinite;
  mask-image: linear-gradient(90deg, transparent, #000 12%, #000 88%, transparent);
}
.viz-rotate i {
  flex: 0 0 26px;
  font: 600 13px/34px var(--mono);
  font-style: normal;
  text-align: center;
  color: var(--accent);
  border: 1px solid var(--wire);
  margin-right: 4px;
  height: 36px;
}

@keyframes rotate { to { transform: translateX(-480px); } }

/* --- visualisation: perlin octaves --------------------------------------- */

.viz-octaves { padding: 20px 0; }
.viz-octaves svg { width: 100%; height: 180px; }
.viz-octaves path {
  fill: none;
  stroke: var(--accent);
  stroke-width: 1.4;
  stroke-linejoin: round;
  opacity: calc(.42 + var(--i) * .18);
  stroke-dasharray: 1;
  stroke-dashoffset: 1;
  animation: draw 7s ease-out infinite;
  animation-delay: calc(var(--i) * .45s);
}

@keyframes draw {
  0% { stroke-dashoffset: 1; }
  42%, 88% { stroke-dashoffset: 0; }
  100% { stroke-dashoffset: 0; opacity: .1; }
}

/* --- visualisation: run length ------------------------------------------- */

.viz-runs { display: grid; gap: 22px; justify-items: center; }
.viz-runs .row { display: flex; }
.viz-runs i {
  width: 24px;
  height: 30px;
  margin-right: 4px;
  overflow: hidden;
  font: 600 12px/28px var(--mono);
  font-style: normal;
  text-align: center;
  color: var(--ink-dim);
  border: 1px solid var(--wire);
  animation: collapse 7s infinite;
  animation-delay: calc(var(--i) * .06s);
}
.viz-runs .single { color: var(--accent); }
.viz-runs .result { display: flex; gap: 10px; }
.viz-runs .result span {
  padding: 7px 12px;
  font: 600 13px/1 var(--mono);
  color: var(--accent);
  border: 1px solid var(--wire-strong);
  opacity: 0;
  animation: appear 7s infinite;
}
.viz-runs .result span:last-child { animation-delay: .25s; }

@keyframes collapse {
  0%, 26% { width: 24px; margin-right: 4px; opacity: 1; }
  46%, 88% { width: 0; margin-right: 0; opacity: 0; border-width: 0; }
  100% { width: 24px; margin-right: 4px; opacity: 1; }
}
@keyframes appear {
  0%, 34% { opacity: 0; transform: translateY(6px); }
  50%, 88% { opacity: 1; transform: none; }
  100% { opacity: 0; }
}

/* --- responsive ---------------------------------------------------------- */

@media (max-width: 1080px) {
  main { padding: 36px 28px 80px; }
  .footer { padding: 24px 28px 36px; }
}

@media (max-width: 860px) {
  .shell { grid-template-columns: minmax(0, 1fr); }
  .menu { display: block; }

  .sidebar {
    position: fixed;
    top: 62px;
    left: 0;
    bottom: 0;
    width: 280px;
    max-height: none;
    background: var(--panel);
    border-right: 1px solid var(--wire-strong);
    transform: translateX(-102%);
    transition: transform .22s ease;
    z-index: 25;
  }
  .sidebar.open { transform: none; }

  .brand-text em { display: none; }
  .search { width: auto; flex: 1; }
  main { padding: 30px 20px 70px; }
  .footer { padding: 22px 20px 34px; }
  .facts { grid-template-columns: repeat(auto-fit, minmax(126px, 1fr)); }
}

@media (max-width: 560px) {
  .topbar { gap: 12px; padding: 0 14px; }
  .brand-text b { font-size: 12px; letter-spacing: .12em; }
  .search kbd { display: none; }
  .stats { gap: 22px; }
  .viz { padding: 20px 10px; }
  .viz-bubble { --bar: 18px; --bar-gap: 7px; }
  .viz-search, .viz-partition { --cell: 26px; --cell-gap: 4px; }
  .viz-search span, .viz-partition span { font-size: 10px; padding: 8px 0; }
  .viz-merge span { min-width: 24px; font-size: 10px; padding: 5px 4px; }
  .viz-compare { grid-template-columns: 1fr; gap: 14px; }
}

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after {
    animation-duration: .001ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: .001ms !important;
  }
  .viz-runs .result span, .viz-fib span, .viz-merge .row { opacity: 1; }
}

@media print {
  .topbar, .sidebar, .figure, .demo { display: none; }
  body { background: #fff; color: #000; }
  main { padding: 0; }
}

/* small diagrams and formulas inside the text */
.prose pre.art {
  margin: 16px 0;
  padding: 14px 16px;
  overflow-x: auto;
  font: 400 12.5px/1.5 var(--mono);
  color: var(--accent);
  background: var(--panel-2);
  border: 1px solid var(--wire);
}

/* --- maps ---------------------------------------------------------------- */

.map-block { margin: 14px 0 0; }

.map {
  margin: 0;
  padding: 14px;
  overflow-x: auto;
  font: 400 11px/1 var(--mono);
  color: rgba(0, 0, 0, .38);
  background: var(--panel-2);
  border: 1px solid var(--wire);
}

.g-deep { background: #0b2f52; }
.g-shallow { background: #17608e; }
.g-beach { background: #d9c48d; }
.g-grass { background: #5c9c46; }
.g-forest { background: #2f6b34; }
.g-rock { background: #83868d; }
.g-snow { background: #e9eef2; }

/* land drawn on water, straight in the recorded output */
.code.output pre.map-coast { background: #0b2f52; }
.code.output pre.map-coast code { color: #7fd06a; }

.legend {
  display: flex;
  flex-wrap: wrap;
  gap: 8px 18px;
  margin: 12px 0 0;
  padding: 0;
  list-style: none;
  font: 400 11px/1 var(--mono);
  letter-spacing: .1em;
  text-transform: uppercase;
  color: var(--ink-faint);
}
.legend li { display: flex; align-items: center; gap: 7px; }
.legend i { width: 12px; height: 12px; border: 1px solid rgba(0, 0, 0, .3); }

/* --- the board of the tile demo ------------------------------------------ */

.demo .board {
  margin: 0;
  padding: 16px;
  overflow-x: auto;
  font: 400 13px/1.15 var(--mono);
  color: var(--accent);
  border-bottom: 1px solid var(--wire);
}
.demo .board i { font-style: normal; color: var(--ink-faint); opacity: .5; }