:root {
  color-scheme: dark;
  font-family: system-ui, -apple-system, "Segoe UI", sans-serif;
  --ink: #f2efe8;
  --purple: #8b5cf6;
  --blue: #3ba3e6;
  /* What the marks and the facets actually look like on the object: the
     shader's PURPLE, BLUE and BONE as they come out after shading, so the
     legend is a picture of the page rather than an approximation of it. */
  --mark-purple: #6b32c2;
  --mark-blue: #1e8ccb;
  --facet: #c9c4b6;
  --panel: #0e1119e8;
}
* { box-sizing: border-box; }
html, body, main { width: 100%; height: 100%; margin: 0; overflow: hidden; }
body {
  overscroll-behavior: none;
  color: var(--ink);
  background: #070810 radial-gradient(120% 90% at 50% 34%, #1b2136 0%, #0d1019 46%, #05060b 100%) fixed;
}
main { position: fixed; inset: 0; }
canvas {
  display: block; width: 100%; height: 100%;
  touch-action: none; cursor: grab; user-select: none;
  -webkit-user-select: none; -webkit-touch-callout: none;
}
body.dragging canvas { cursor: grabbing; }
[hidden] { display: none !important; }

/* Controls -------------------------------------------------------------- */
/* left/right: 0 with auto inline margins, not left: 50% with a transform: an
   auto-width fixed box anchored at left: 50% may only use the half of the
   viewport to its right, which wrapped the bar onto three rows on a phone. */
#controls {
  position: fixed; left: 0; right: 0; bottom: max(18px, env(safe-area-inset-bottom));
  margin-inline: auto; width: max-content;
  display: flex; flex-wrap: wrap; justify-content: center; align-items: center; gap: 4px;
  max-width: min(600px, calc(100vw - 16px));
  padding: 6px; border: 1px solid #ffffff2e; border-radius: 26px;
  background: var(--panel); box-shadow: 0 6px 34px #00000099;
  -webkit-backdrop-filter: blur(16px); backdrop-filter: blur(16px);
  transition: opacity .55s ease;
}
#controls .group {
  display: flex; align-items: center; gap: 2px;
  border-radius: 999px; background: #ffffff14;
}
#level-label {
  min-width: 5.6em; padding: 0 2px; text-align: center;
  font-size: 13px; letter-spacing: .02em; font-variant-numeric: tabular-nums;
}
button {
  min-width: 42px; min-height: 42px;
  display: inline-flex; align-items: center; justify-content: center;
  border: 0; border-radius: 999px; padding: 9px;
  background: transparent; color: inherit; font: inherit; cursor: pointer;
  -webkit-tap-highlight-color: transparent;
}
button svg { width: 21px; height: 21px; fill: none; stroke: currentColor; stroke-width: 1.7; stroke-linecap: round; stroke-linejoin: round; }
button:hover { background: #ffffff1f; }
button:focus-visible { outline: 2px solid var(--ink); outline-offset: 2px; }
button:disabled { opacity: .35; cursor: default; }
button[aria-pressed="true"] { background: #ffffff2b; }
/* Holds its place in the bar, so nothing moves when it comes and goes. */
button.invisible { visibility: hidden; pointer-events: none; }
body.quiet #controls { opacity: 0; pointer-events: none; }
body.quiet #controls:focus-within { opacity: 1; pointer-events: auto; }
/* A touch screen has no hover to bring the bar back, so it only dims. */
@media (pointer: coarse) {
  body.quiet #controls { opacity: .3; pointer-events: auto; }
}

/* Caption --------------------------------------------------------------- */
#caption {
  position: fixed;
  top: max(12px, env(safe-area-inset-top));
  left: max(12px, env(safe-area-inset-left));
  width: min(392px, calc(100vw - 24px));
  border: 1px solid #ffffff24; border-radius: 16px;
  background: var(--panel); box-shadow: 0 6px 34px #0009;
  -webkit-backdrop-filter: blur(16px); backdrop-filter: blur(16px);
}
#caption summary {
  display: flex; align-items: center; gap: 9px;
  padding: 11px 14px; font-size: 14px; font-weight: 600; letter-spacing: .01em;
  cursor: pointer; list-style: none; border-radius: 16px;
}
#caption summary::-webkit-details-marker { display: none; }
#caption summary:focus-visible { outline: 2px solid var(--ink); outline-offset: -3px; }
#caption .dot {
  width: 9px; height: 9px; border-radius: 3px; flex: none;
  background: linear-gradient(135deg, var(--purple), var(--blue));
}
#caption .chev {
  margin-left: auto; width: 9px; height: 9px; flex: none;
  border-right: 1.7px solid currentColor; border-bottom: 1.7px solid currentColor;
  transform: rotate(45deg) translate(-2px, -2px); opacity: .65;
  transition: transform .2s ease;
}
#caption[open] .chev { transform: rotate(225deg) translate(-2px, -2px); }
#caption .body {
  max-height: min(62vh, 620px); overflow-y: auto; overscroll-behavior: contain;
  padding: 0 15px 14px; font-size: 13px; line-height: 1.52; color: #ddd8ceef;
}
/* It scrolls, so it is focusable and the arrow keys reach it. */
#caption .body:focus-visible { outline: 2px solid var(--ink); outline-offset: -3px; }
/* A fade at the foot of the panel, so it is clear the text scrolls. */
#caption[open]::after {
  content: ""; position: absolute; left: 1px; right: 1px; bottom: 1px; height: 22px;
  border-radius: 0 0 15px 15px; pointer-events: none;
  background: linear-gradient(to top, #0e1119f2, #0e111900);
}
#caption p { margin: 0 0 9px; }
#caption b { color: var(--ink); }
#caption a { color: #9ec6f5; }
#caption .rule {
  padding: 7px 10px; border-radius: 9px; background: #ffffff10;
  color: var(--ink); font-size: 12.5px; text-align: center;
}
#caption .credit { margin-top: 12px; padding-top: 10px; border-top: 1px solid #ffffff1c; font-size: 11.5px; color: #b9b3a9; }
/* One facet each, with the glyph at exactly the proportions the shader draws:
   the marked corner at the top right, the arrow along the facet's diagonal. */
#caption .legend { display: flex; flex-wrap: wrap; gap: 8px 14px; margin: 2px 0 11px; padding: 0; list-style: none; }
#caption .legend li { display: flex; align-items: center; gap: 6px; font-size: 12px; }
#caption .legend svg { width: 36px; height: 36px; flex: none; }
#caption .legend .tile { fill: var(--facet); }
#caption .legend .shaft, #caption .legend .barb { fill: none; stroke-linecap: round; }
#caption .legend .shaft { stroke-width: 2.99; }
#caption .legend .barb { stroke-width: 2.86; }
#caption .legend polygon { stroke: none; }
#caption .legend .purple { stroke: var(--mark-purple); fill: var(--mark-purple); }
#caption .legend .blue { stroke: var(--mark-blue); fill: var(--mark-blue); }

/* Notice and stats ------------------------------------------------------ */
#notice {
  position: fixed; top: 50%; left: 50%; transform: translate(-50%, -50%);
  max-width: min(420px, calc(100% - 40px)); padding: 16px 22px;
  border-radius: 14px; background: #060810ee; text-align: center; font-size: 15px; line-height: 1.5;
}
#hud {
  position: fixed; right: max(12px, env(safe-area-inset-right)); top: max(12px, env(safe-area-inset-top));
  padding: 6px 10px; border-radius: 8px; background: #060810cc;
  font: 11.5px/1.45 ui-monospace, SFMono-Regular, Menlo, monospace; color: #cfcabf;
  pointer-events: none; text-align: right;
}
noscript { position: fixed; inset: 40% 20px auto; padding: 20px; text-align: center; background: #060810; border-radius: 12px; }

@media (max-width: 720px) {
  #caption { width: calc(100vw - 20px); left: 10px; }
  #caption .body { max-height: min(52vh, 460px); }
  #controls { gap: 2px; padding: 5px; }
  button { min-width: 40px; min-height: 40px; padding: 8px; }
  #level-label { font-size: 12px; min-width: 5.2em; }
}
@media (prefers-reduced-motion: reduce) {
  #controls, #caption .chev { transition: none; }
}