/* Frontier — an interactive essay on pathfinding.
   Vanilla CSS. No build step. Built against a WCAG 2.2 AA pattern set. */

/* ---- Design tokens ---------------------------------------------------- */
:root {
  --bg:        #fcfbf9;
  --bg-sunk:   #f1efe9;
  --ink:       #1c1b19;
  --ink-soft:  #514e47;   /* 7.4:1 on --bg */
  --rule:      #cdc8bc;
  --accent:    #2f5fd0;   /* frontier / links — 5.0:1 on --bg */
  --accent-d:  #284fab;   /* 6.8:1 on --bg, for link text */
  --path:      #b4540a;   /* path — warm, 4.6:1 on --bg */
  --visited:   #c3d0ec;
  --visited-d: #5d74ad;
  --wall:      #292826;
  --goal:      #1c7a43;
  --focus:     #0b3ad6;

  --serif: "Iowan Old Style", "Palatino Linotype", Palatino, Georgia, serif;
  --sans:  -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  --mono:  "SF Mono", "JetBrains Mono", "Consolas", ui-monospace, monospace;
  --maxw:  43rem;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg:        #15161a;
    --bg-sunk:   #1f2129;
    --ink:       #ecebe6;
    --ink-soft:  #b0ada4;
    --rule:      #3a3b45;
    --accent:    #8ba8f2;
    --accent-d:  #acc0f7;
    --path:      #f0a35a;
    --visited:   #2d3a59;
    --visited-d: #6a7fab;
    --wall:      #0b0b0d;
    --goal:      #5fc98a;
    --focus:     #aabdf8;
  }
}

/* ---- Reset & base ----------------------------------------------------- */
*, *::before, *::after { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; }

body {
  margin: 0;
  background: var(--bg);
  color: var(--ink);
  font-family: var(--serif);
  font-size: 1.18rem;
  line-height: 1.62;
  text-rendering: optimizeLegibility;
  -webkit-font-smoothing: antialiased;
}

.skip-link {
  position: absolute;
  left: 0.5rem;
  top: -3.5rem;
  background: var(--ink);
  color: var(--bg);
  padding: 0.55rem 0.95rem;
  border-radius: 7px;
  font-family: var(--sans);
  font-size: 0.95rem;
  z-index: 60;
  transition: top 0.15s ease;
}
.skip-link:focus { top: 0.5rem; }

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

/* ---- Layout ----------------------------------------------------------- */
.wrap { max-width: var(--maxw); margin: 0 auto; padding: 0 1.25rem; }

.site-head { border-bottom: 1px solid var(--rule); }
.site-head .wrap {
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  gap: 0.3rem 1.1rem;
  padding: 1.05rem 1.25rem;
}
.brand {
  font-family: var(--sans);
  font-weight: 800;
  font-size: 1.05rem;
  letter-spacing: 0.01em;
  color: var(--ink);
  text-decoration: none;
}
.brand::before { content: "◆"; color: var(--accent); margin-right: 0.4rem; }
.tagline { font-family: var(--sans); font-size: 0.85rem; color: var(--ink-soft); }

/* Parts navigation */
.parts { border-bottom: 1px solid var(--rule); background: var(--bg-sunk); }
.parts ol {
  max-width: var(--maxw);
  margin: 0 auto;
  padding: 0.45rem 1.25rem;
  list-style: none;
  display: flex;
  flex-wrap: wrap;
  gap: 0.25rem 0.35rem;
  font-family: var(--sans);
  font-size: 0.82rem;
  counter-reset: part;
}
.parts a, .parts span {
  display: inline-block;
  padding: 0.32rem 0.6rem;
  border-radius: 6px;
  text-decoration: none;
  color: var(--ink-soft);
  border: 1px solid transparent;
}
.parts a:hover { color: var(--accent-d); background: var(--bg); }
.parts [aria-current="page"] {
  background: var(--accent);
  color: #fff;
  font-weight: 700;
}
@media (prefers-color-scheme: dark) {
  .parts [aria-current="page"] { color: #15161a; }
}

/* ---- Prose ------------------------------------------------------------ */
main { padding: 2.4rem 0 3.5rem; }
main:focus { outline: none; }

.eyebrow {
  font-family: var(--sans);
  font-size: 0.78rem;
  font-weight: 800;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--accent-d);
  margin: 0 0 0.5rem;
}

h1 {
  font-size: 2.55rem;
  line-height: 1.1;
  font-weight: 700;
  margin: 0 0 0.55rem;
  letter-spacing: -0.015em;
}
h2 {
  font-size: 1.62rem;
  line-height: 1.2;
  margin: 2.7rem 0 0.7rem;
  letter-spacing: -0.005em;
}
h3 {
  font-family: var(--sans);
  font-size: 1.04rem;
  margin: 1.9rem 0 0.4rem;
}

p { margin: 0 0 1.1rem; }
a { color: var(--accent-d); text-underline-offset: 0.16em; }

.lede {
  font-size: 1.3rem;
  line-height: 1.5;
  color: var(--ink-soft);
  margin-bottom: 1.8rem;
}

strong { font-weight: 700; }
em { font-style: italic; }
code {
  font-family: var(--mono);
  font-size: 0.84em;
  background: var(--bg-sunk);
  padding: 0.1rem 0.34rem;
  border-radius: 4px;
}

.note {
  border-left: 3px solid var(--accent);
  padding: 0.15rem 0 0.15rem 1rem;
  margin: 1.5rem 0;
  color: var(--ink-soft);
  font-size: 1.03rem;
}

ul.prose, ol.prose { margin: 0 0 1.1rem; padding-left: 1.3rem; }
ul.prose li, ol.prose li { margin: 0.3rem 0; }

/* ---- Figure / demo container ----------------------------------------- */
.figure {
  margin: 2rem 0;
  border: 1px solid var(--rule);
  border-radius: 11px;
  background: var(--bg);
  overflow: clip;
}
.figure-cap {
  font-family: var(--sans);
  font-size: 0.82rem;
  line-height: 1.5;
  color: var(--ink-soft);
  padding: 0.7rem 1rem;
  border-top: 1px solid var(--rule);
  background: var(--bg-sunk);
}
.figure-cap b { color: var(--ink); }
figure { margin: 0; }
figcaption { font: inherit; }

/* ---- Controls --------------------------------------------------------- */
.controls {
  display: flex;
  flex-wrap: wrap;
  gap: 0.55rem;
  align-items: center;
  padding: 0.85rem 1rem;
  border-bottom: 1px solid var(--rule);
  font-family: var(--sans);
}
.btn {
  font-family: var(--sans);
  font-size: 0.92rem;
  font-weight: 600;
  color: var(--ink);
  background: var(--bg);
  border: 1px solid var(--rule);
  border-radius: 7px;
  padding: 0.46rem 0.85rem;
  cursor: pointer;
  min-height: 2.5rem;
}
.btn:hover { border-color: var(--accent); color: var(--accent-d); }
.btn:active { transform: translateY(1px); }
.btn[aria-pressed="true"] {
  background: var(--accent);
  border-color: var(--accent);
  color: #fff;
}
.btn-primary { background: var(--accent); border-color: var(--accent); color: #fff; }
.btn-primary:hover { background: var(--accent-d); border-color: var(--accent-d); color: #fff; }
.btn:disabled { opacity: 0.42; cursor: not-allowed; }
.btn:disabled:hover { border-color: var(--rule); color: var(--ink); }
@media (prefers-color-scheme: dark) {
  .btn-primary, .btn[aria-pressed="true"] { color: #15161a; }
}

.control-group { display: flex; gap: 0.35rem; align-items: center; }
.control-group.sep {
  border-left: 1px solid var(--rule);
  padding-left: 0.6rem;
  margin-left: 0.1rem;
}

.field {
  display: flex;
  align-items: center;
  gap: 0.45rem;
  font-size: 0.86rem;
  color: var(--ink-soft);
}
.field label { font-weight: 600; }
.field input[type="range"] { width: 7rem; accent-color: var(--accent); }
.field output {
  font-family: var(--mono);
  font-size: 0.84rem;
  color: var(--ink);
  min-width: 2.2rem;
}

/* Tool radio group (radiogroup) */
.toolset {
  display: flex;
  border: 1px solid var(--rule);
  border-radius: 8px;
  overflow: clip;
}
.toolset [role="radio"] {
  font-family: var(--sans);
  font-size: 0.88rem;
  font-weight: 600;
  background: var(--bg);
  color: var(--ink);
  border: 0;
  border-right: 1px solid var(--rule);
  padding: 0.45rem 0.7rem;
  min-height: 2.5rem;
  cursor: pointer;
}
.toolset [role="radio"]:last-child { border-right: 0; }
.toolset [role="radio"][aria-checked="true"] { background: var(--accent); color: #fff; }
.toolset [role="radio"]:focus-visible { outline: 3px solid var(--focus); outline-offset: -3px; }
@media (prefers-color-scheme: dark) {
  .toolset [role="radio"][aria-checked="true"] { color: #15161a; }
}

/* ---- Canvas stage ----------------------------------------------------- */
.grid-stage { padding: 1rem; display: flex; justify-content: center; }
.canvas-wrap {
  width: 100%;
  max-width: 30rem;
  display: flex;
  flex-direction: column;
  gap: 0.6rem;
}
canvas.figure-canvas {
  width: 100%;
  aspect-ratio: 1;
  display: block;
  border: 2px solid var(--rule);
  border-radius: 7px;
  background: var(--bg-sunk);
  image-rendering: pixelated;
  image-rendering: crisp-edges;
  touch-action: none;
}
canvas.figure-canvas:focus-visible {
  outline: 3px solid var(--focus);
  outline-offset: 3px;
}
.canvas-pair { display: flex; gap: 0.6rem; flex-wrap: wrap; }
.canvas-pair .canvas-cell { flex: 1 1 8rem; min-width: 7rem; }
.canvas-cell figcaption {
  font-family: var(--sans);
  font-size: 0.76rem;
  color: var(--ink-soft);
  margin-top: 0.3rem;
  text-align: center;
}

/* Data fallback — a non-canvas representation of the figure. */
.data-fallback {
  border-top: 1px solid var(--rule);
  font-family: var(--sans);
}
.data-fallback summary {
  cursor: pointer;
  padding: 0.7rem 1rem;
  font-size: 0.86rem;
  font-weight: 600;
  color: var(--accent-d);
}
.data-fallback summary:focus-visible { outline: 3px solid var(--focus); outline-offset: -3px; }
.data-fallback .data-body {
  padding: 0.2rem 1rem 0.9rem;
  font-size: 0.86rem;
  color: var(--ink-soft);
}
.data-fallback dl {
  display: grid;
  grid-template-columns: auto 1fr;
  gap: 0.25rem 1rem;
  margin: 0.4rem 0;
}
.data-fallback dt { font-weight: 600; color: var(--ink); }
.data-fallback dd { margin: 0; font-family: var(--mono); }

/* ---- Legend ----------------------------------------------------------- */
.legend {
  display: flex;
  flex-wrap: wrap;
  gap: 0.45rem 1.1rem;
  margin: 0;
  padding: 0.8rem 1rem;
  border-top: 1px solid var(--rule);
  font-family: var(--sans);
  font-size: 0.81rem;
  color: var(--ink-soft);
  list-style: none;
}
.legend li { display: flex; align-items: center; gap: 0.4rem; }
.swatch {
  width: 1.15rem; height: 1.15rem;
  border-radius: 3px;
  border: 1px solid var(--rule);
  display: inline-flex;
  align-items: center;
  justify-content: center;
  font-size: 0.7rem;
  font-weight: 800;
  flex: none;
}
.swatch-grad {
  width: 5rem;
  background: linear-gradient(90deg, #10131a, #f3f1ec);
}

/* ---- Stats & status --------------------------------------------------- */
.stats {
  display: flex;
  flex-wrap: wrap;
  gap: 0.35rem 1.5rem;
  padding: 0.75rem 1rem;
  border-top: 1px solid var(--rule);
  font-family: var(--sans);
  font-size: 0.87rem;
  color: var(--ink-soft);
}
.stat b {
  font-family: var(--mono);
  font-size: 1.08rem;
  color: var(--accent-d);
  margin-right: 0.25rem;
}
.status {
  font-family: var(--sans);
  font-size: 0.9rem;
  padding: 0.72rem 1rem;
  border-top: 1px solid var(--rule);
  background: var(--bg-sunk);
  min-height: 1.3rem;
  color: var(--ink-soft);
}
.status[data-tone="win"]  { color: var(--goal); font-weight: 700; }
.status[data-tone="fail"] { color: var(--path); font-weight: 700; }

/* ---- Pager / footer --------------------------------------------------- */
.pager {
  display: flex;
  justify-content: space-between;
  gap: 1rem;
  margin-top: 3rem;
  border-top: 1px solid var(--rule);
  padding-top: 1.5rem;
}
.pager a {
  font-family: var(--sans);
  text-decoration: none;
  font-size: 0.96rem;
  max-width: 47%;
}
.pager .dir {
  display: block;
  font-size: 0.74rem;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--ink-soft);
  margin-bottom: 0.15rem;
}
.pager .ttl { font-weight: 700; color: var(--accent-d); }
.pager .next { text-align: right; margin-left: auto; }
.pager span[aria-disabled="true"] { opacity: 0.4; }

.site-foot {
  border-top: 1px solid var(--rule);
  padding: 1.7rem 0;
  font-family: var(--sans);
  font-size: 0.83rem;
  color: var(--ink-soft);
}
.site-foot a { color: var(--accent-d); }

/* ---- Utility ---------------------------------------------------------- */
.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;
}
.kbd {
  font-family: var(--mono);
  font-size: 0.8em;
  background: var(--bg-sunk);
  border: 1px solid var(--rule);
  border-bottom-width: 2px;
  border-radius: 4px;
  padding: 0.05rem 0.36rem;
  white-space: nowrap;
}

@media (max-width: 33rem) {
  body { font-size: 1.08rem; }
  h1 { font-size: 2.05rem; }
  .lede { font-size: 1.14rem; }
  .field input[type="range"] { width: 5rem; }
  .controls { gap: 0.4rem; }
}

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after {
    transition-duration: 0.01ms !important;
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
  }
  .skip-link { transition: none; }
}

/* ---- Meridian: globe + flat-map layout -------------------------------- */
.map-stack { display: flex; flex-direction: column; gap: 0.9rem; width: 100%; max-width: 33rem; }
.map-row { display: flex; gap: 0.9rem; align-items: flex-start; flex-wrap: wrap; }
.globe-cell { flex: 0 0 11rem; }
.map-cell   { flex: 1 1 16rem; min-width: 14rem; }
.cell-head {
  font-family: var(--sans);
  font-size: 0.78rem;
  font-weight: 700;
  letter-spacing: 0.04em;
  text-transform: uppercase;
  color: var(--ink-soft);
  margin: 0 0 0.3rem;
}
canvas.figure-canvas.globe { aspect-ratio: 1; max-width: 11rem; cursor: grab; }
canvas.figure-canvas.globe:active { cursor: grabbing; }
canvas.figure-canvas.map   { aspect-ratio: 2 / 1; max-width: 100%; }
canvas.figure-canvas.map.tall { aspect-ratio: 1 / 1; }


/* ---- Single-scroll dissertation layout -------------------------------- */
.progress {
  position: fixed;
  top: 0; left: 0; right: 0;
  height: 3px;
  background: transparent;
  z-index: 70;
}
.progress > span {
  display: block;
  height: 100%;
  width: 0;
  background: var(--accent);
}

.docmeta {
  font-family: var(--sans);
  font-size: 0.86rem;
  color: var(--ink-soft);
  border-bottom: 1px solid var(--rule);
  padding-bottom: 1.1rem;
  margin-bottom: 1.6rem;
}
.docmeta b { color: var(--ink); font-weight: 700; }

.abstract {
  background: var(--bg-sunk);
  border: 1px solid var(--rule);
  border-radius: 11px;
  padding: 1.2rem 1.4rem;
  margin: 1.8rem 0 2.2rem;
}
.abstract h2 {
  font-family: var(--sans);
  font-size: 0.82rem;
  letter-spacing: 0.13em;
  text-transform: uppercase;
  color: var(--accent-d);
  margin: 0 0 0.5rem;
}
.abstract p { font-size: 1.06rem; margin-bottom: 0.6rem; }
.abstract p:last-child { margin-bottom: 0; }

/* table of contents */
.toc {
  border: 1px solid var(--rule);
  border-radius: 11px;
  padding: 1rem 1.3rem 1.2rem;
  margin: 2rem 0 2.6rem;
  font-family: var(--sans);
}
.toc h2 {
  font-size: 0.82rem;
  letter-spacing: 0.13em;
  text-transform: uppercase;
  color: var(--accent-d);
  margin: 0 0 0.6rem;
}
.toc ol { margin: 0; padding-left: 1.4rem; }
.toc li { margin: 0.28rem 0; font-size: 0.96rem; }
.toc a { color: var(--ink); text-decoration: none; }
.toc a:hover { color: var(--accent-d); text-decoration: underline; }

/* numbered sections */
.essay section { scroll-margin-top: 1.5rem; }
.essay section > h2 {
  border-top: 1px solid var(--rule);
  padding-top: 1.8rem;
  margin-top: 3rem;
}
.secnum {
  font-family: var(--mono);
  font-size: 0.9rem;
  color: var(--accent-d);
  margin-right: 0.5rem;
}

/* references */
.references { margin-top: 1rem; }
.references ol { padding-left: 1.6rem; }
.references li {
  margin: 0.5rem 0;
  font-size: 0.96rem;
  line-height: 1.5;
}
.references li::marker { color: var(--ink-soft); }
.cite {
  font-variant-numeric: tabular-nums;
  white-space: nowrap;
}
a.cite { color: var(--accent-d); text-decoration: none; }
a.cite:hover { text-decoration: underline; }

/* a key-term definition aside */
.term {
  border-left: 3px solid var(--accent);
  padding: 0.1rem 0 0.1rem 1rem;
  margin: 1.4rem 0;
}
.term dt {
  font-family: var(--sans);
  font-weight: 700;
  font-size: 0.95rem;
  color: var(--ink);
}
.term dd { margin: 0.2rem 0 0; color: var(--ink-soft); font-size: 1.02rem; }

/* back-to-top */
.totop {
  display: inline-block;
  margin-top: 1rem;
  font-family: var(--sans);
  font-size: 0.85rem;
  color: var(--accent-d);
  text-decoration: none;
}