Light Show Choreographer

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<!doctype html>
<html lang="en">
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1, viewport-fit=cover">
<title>Light Show Choreographer — sloprun.dev</title>
<style>
/* ── sloprun design tokens (verbatim from demos/tokens.css) ───────────────── */
:root {
  --bg: #F6F6F3;          /* neutral paper, not cream */
  --surface: #FFFFFF;
  --ink: #1A1D21;
  --muted: #5A6068;
  --line: #E3E2DC;
  --accent: #C05600;      /* phosphor amber, darkened for light bg */
  --accent-soft: #FFF3E6;
  --run: #1A7F37;         /* earned green */
  --run-soft: #E7F4EA;
  --danger: #C93C37;
  --radius: 10px;
  --font-sans: system-ui, -apple-system, "Segoe UI", sans-serif;
  --font-mono: ui-monospace, "SF Mono", "Cascadia Code", Menlo, Consolas, monospace;
}
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --bg: #14161A; --surface: #1C1F26; --ink: #E8E6E1; --muted: #9AA0A8;
    --line: #2A2E36; --accent: #FFB454; --accent-soft: #2A2118;
    --run: #3FB950; --run-soft: #16281B; --danger: #F47067;
  }
}
:root[data-theme="dark"] {
  --bg: #14161A; --surface: #1C1F26; --ink: #E8E6E1; --muted: #9AA0A8;
  --line: #2A2E36; --accent: #FFB454; --accent-soft: #2A2118;
  --run: #3FB950; --run-soft: #16281B; --danger: #F47067;
}
body { background: var(--bg); color: var(--ink); font-family: var(--font-sans); }
/* ── end tokens ───────────────────────────────────────────────────────────── */

/* demo-local additions. The sky is a stage: dark in both themes, but tuned —
   dusk-blue under the light theme, deep night under the dark one. */
:root {
  --scrim: rgba(246,246,243,.88);
  --shadow: 0 1px 2px rgba(26,29,33,.05);
  --sky-top: #222839;
  --sky-bot: #444C63;
  --dot: #FFC978;
  --core: #FFF7EA;
  --glow-a: .58;
  --trail-a: .34;
  --star-a: .42;
}
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --scrim: rgba(20,22,26,.88);
    --shadow: 0 1px 2px rgba(0,0,0,.35);
    --sky-top: #07090D; --sky-bot: #161B25;
    --dot: #FFB454; --core: #FFFFFF;
    --glow-a: .84; --trail-a: .52; --star-a: .95;
  }
}
:root[data-theme="dark"] {
  --scrim: rgba(20,22,26,.88);
  --shadow: 0 1px 2px rgba(0,0,0,.35);
  --sky-top: #07090D; --sky-bot: #161B25;
  --dot: #FFB454; --core: #FFFFFF;
  --glow-a: .84; --trail-a: .52; --star-a: .95;
}

* { box-sizing: border-box; }
html, body { margin: 0; padding: 0; }
html { -webkit-text-size-adjust: 100%; }
body { min-height: 100%; overflow-x: hidden; }

.wrap {
  max-width: 1140px; margin: 0 auto;
  padding: 22px 16px 26px;
  display: flex; flex-direction: column; gap: 16px;
}

h1 { margin: 0 0 6px; font-size: clamp(21px, 3.6vw, 29px); letter-spacing: -.021em; line-height: 1.15; }
.lede { margin: 0; max-width: 68ch; color: var(--muted); font-size: 14.5px; line-height: 1.55; }
.lede b { color: var(--ink); font-weight: 600; }

.stage { display: grid; grid-template-columns: minmax(0,1fr) 300px; gap: 16px; align-items: start; }
@media (max-width: 900px) { .stage { grid-template-columns: minmax(0,1fr); } }

.field {
  position: relative; overflow: hidden;
  border: 1px solid var(--line); border-radius: var(--radius);
  background: var(--sky-top);
  aspect-ratio: 16 / 10; box-shadow: var(--shadow);
}
@media (max-width: 900px) { .field { aspect-ratio: 4 / 3; } }
@media (max-width: 560px) { .field { aspect-ratio: 5 / 4; } }
canvas { display: block; width: 100%; height: 100%; touch-action: manipulation; }

.hint {
  position: absolute; left: 10px; bottom: 10px; pointer-events: none;
  font-family: var(--font-mono); font-size: 11px; letter-spacing: .01em;
  color: var(--muted); background: var(--scrim);
  border: 1px solid var(--line); border-radius: 999px; padding: 5px 10px;
  transition: opacity .45s ease; max-width: calc(100% - 20px);
}
.hint[hidden] { display: none; }
@media (max-width: 560px) { .hint { display: none; } }
.hint.gone { opacity: 0; }

.marquee {
  position: absolute; left: 10px; top: 10px; pointer-events: none;
  display: flex; align-items: baseline; gap: 8px;
  font-family: var(--font-mono); font-size: 11px; letter-spacing: .08em;
  text-transform: uppercase; color: var(--muted);
  background: var(--scrim); border: 1px solid var(--line);
  border-radius: 999px; padding: 5px 11px; max-width: calc(100% - 20px);
}
.marquee b {
  color: var(--ink); font-weight: 600; letter-spacing: .04em;
  overflow: hidden; text-overflow: ellipsis; white-space: nowrap;
}

.panel { display: flex; flex-direction: column; gap: 12px; }
.card {
  background: var(--surface); border: 1px solid var(--line);
  border-radius: var(--radius); padding: 12px 13px; box-shadow: var(--shadow);
}
.card h2 {
  margin: 0 0 10px; font-family: var(--font-mono); font-size: 10.5px;
  letter-spacing: .1em; text-transform: uppercase; color: var(--muted); font-weight: 600;
}

.stats { display: grid; grid-template-columns: repeat(3, minmax(0,1fr)); gap: 10px; }
.stat { display: flex; flex-direction: column; gap: 2px; min-width: 0; }
.stat .v {
  font-family: var(--font-mono); font-size: 20px; line-height: 1.05;
  font-variant-numeric: tabular-nums; letter-spacing: -.02em;
}
.stat .k {
  font-family: var(--font-mono); font-size: 9.5px; letter-spacing: .09em;
  text-transform: uppercase; color: var(--muted);
}

.meter { display: flex; align-items: center; gap: 8px; margin-top: 12px; }
.meter .lbl {
  font-family: var(--font-mono); font-size: 9.5px; letter-spacing: .09em;
  text-transform: uppercase; color: var(--muted); flex: none;
}
.meter .bar {
  flex: 1 1 auto; height: 6px; border-radius: 3px;
  background: var(--line); overflow: hidden;
}
.meter .bar i {
  display: block; height: 100%; width: 0%;
  background: var(--accent); border-radius: 3px;
  transition: width .1s linear;
}
.meter .bar.done i { background: var(--run); }
.meter .num {
  font-family: var(--font-mono); font-size: 11px; color: var(--ink);
  font-variant-numeric: tabular-nums; min-width: 4ch; text-align: right; flex: none;
}

.pill {
  display: inline-flex; align-items: center; gap: 6px; margin-top: 11px;
  font-family: var(--font-mono); font-size: 11px; letter-spacing: .04em;
  padding: 3px 9px 3px 7px; border-radius: 999px;
  border: 1px solid var(--line); color: var(--muted); background: var(--bg);
}
.pill .dot { width: 7px; height: 7px; border-radius: 50%; background: var(--muted); flex: none; }
.pill.on { color: var(--run); background: var(--run-soft); border-color: transparent; }
.pill.on .dot { background: var(--run); }

.cap { margin: 9px 0 0; font-size: 11.5px; line-height: 1.45; color: var(--muted); }
.cap b { color: var(--ink); font-weight: 600; }
.cap .mono { font-family: var(--font-mono); font-variant-numeric: tabular-nums; }

.chips { display: grid; grid-template-columns: repeat(3, minmax(0,1fr)); gap: 7px; }
@media (max-width: 380px) { .chips { grid-template-columns: repeat(2, minmax(0,1fr)); } }
.chips button { width: 100%; padding: 7px 6px; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
.chips button[aria-pressed="true"] {
  background: var(--accent-soft); color: var(--accent); border-color: var(--accent); font-weight: 600;
}

.wordrow { display: flex; gap: 7px; margin-top: 10px; }
input[type=text] {
  flex: 1 1 auto; min-width: 0; font: inherit; font-size: 13px;
  font-family: var(--font-mono); text-transform: uppercase; letter-spacing: .06em;
  color: var(--ink); background: var(--bg);
  border: 1px solid var(--line); border-radius: 8px; padding: 7px 9px;
}
input[type=text]:focus-visible { outline: 2px solid var(--accent); outline-offset: 1px; border-color: var(--accent); }

.ctl { display: block; }
.ctl-top { display: flex; justify-content: space-between; align-items: baseline; gap: 8px; margin-bottom: 3px; }
.ctl-top label { font-size: 13px; }
.ctl-top .val {
  font-family: var(--font-mono); font-size: 12px; color: var(--muted);
  font-variant-numeric: tabular-nums;
}
input[type=range] {
  -webkit-appearance: none; appearance: none; display: block;
  width: 100%; height: 20px; margin: 0; background: transparent; cursor: pointer;
}
input[type=range]::-webkit-slider-runnable-track { height: 4px; border-radius: 2px; background: var(--line); }
input[type=range]::-webkit-slider-thumb {
  -webkit-appearance: none; width: 15px; height: 15px; margin-top: -5.5px;
  border-radius: 50%; background: var(--accent); border: 2px solid var(--surface);
  box-shadow: 0 0 0 1px var(--line);
}
input[type=range]::-moz-range-track { height: 4px; border-radius: 2px; background: var(--line); }
input[type=range]::-moz-range-thumb {
  width: 13px; height: 13px; border-radius: 50%; background: var(--accent);
  border: 2px solid var(--surface); box-shadow: 0 0 0 1px var(--line);
}
input[type=range]:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; border-radius: 6px; }
input[type=range]:disabled { cursor: not-allowed; opacity: .45; }

button {
  font: inherit; font-size: 13px; font-family: var(--font-sans);
  color: var(--ink); background: var(--surface);
  border: 1px solid var(--line); border-radius: 8px;
  padding: 7px 11px; cursor: pointer; line-height: 1.2;
  transition: border-color .12s ease, color .12s ease, background .12s ease;
}
button:hover:not(:disabled) { border-color: var(--accent); color: var(--accent); }
button:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; }
button:disabled { opacity: .42; cursor: not-allowed; }
button.primary { background: var(--accent); color: var(--surface); border-color: var(--accent); font-weight: 600; }
button.primary:hover:not(:disabled) { color: var(--surface); filter: brightness(1.07); }

.row { display: flex; flex-wrap: wrap; gap: 7px; margin-top: 12px; }
.row > button { flex: 1 1 auto; }

.switch { display: flex; align-items: center; gap: 9px; cursor: pointer; font-size: 13px; margin-top: 12px; }
.switch input { position: absolute; opacity: 0; width: 0; height: 0; }
.track {
  width: 34px; height: 19px; border-radius: 999px; background: var(--line);
  border: 1px solid var(--line); position: relative; flex: none; transition: background .15s ease;
}
.track::after {
  content: ""; position: absolute; top: 1.5px; left: 2px; width: 14px; height: 14px;
  border-radius: 50%; background: var(--surface); transition: transform .15s ease;
  box-shadow: 0 1px 2px rgba(0,0,0,.25);
}
.switch input:checked + .track { background: var(--accent); border-color: var(--accent); }
.switch input:checked + .track::after { transform: translateX(15px); }
.switch input:focus-visible + .track { outline: 2px solid var(--accent); outline-offset: 2px; }
.switch input:disabled + .track { opacity: .45; }
.switch.off { cursor: not-allowed; color: var(--muted); }
.ctl.off .ctl-top label, .ctl.off .ctl-top .val { color: var(--muted); }

.note {
  margin: 11px 0 0; font-size: 11.5px; line-height: 1.45; color: var(--muted);
  border-left: 2px solid var(--line); padding-left: 9px;
}
.note[hidden] { display: none; }

footer {
  font-family: var(--font-mono); font-size: 11px; color: var(--muted);
  letter-spacing: .05em; padding-top: 2px;
}

.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 (prefers-reduced-motion: reduce) {
  *, *::before, *::after { transition-duration: .001ms !important; animation-duration: .001ms !important; }
}
</style>
</head>
<body>
<div class="wrap">

  <header>
    <h1>Light Show Choreographer</h1>
    <p class="lede">
      Two hundred little lights over a park at dusk. Pick a shape and each light works out
      <b>its own route</b> to a spot in it — eased on the way in, nudged aside mid-flight
      whenever a neighbour crowds it. <b>Type a word</b> and the lights spell it.
      <span id="ledeTour">The show is already touring; take it over whenever you like.</span>
    </p>
  </header>

  <main class="stage">

    <div class="field" id="field">
      <canvas id="c" role="img" aria-label="Night sky with 200 glowing lights arranging themselves into shapes.">
        An animation of 200 glowing lights forming shapes. Your browser does not support canvas.
      </canvas>
      <div class="marquee" aria-hidden="true">now showing&nbsp;<b id="mName">Circle</b></div>
      <div class="hint" id="hint">move your pointer over the sky to part the lights</div>
    </div>

    <div class="panel">

      <section class="card" aria-label="Show readout">
        <h2>Readout</h2>
        <div class="stats">
          <div class="stat"><span class="v" id="sLights">200</span><span class="k">lights</span></div>
          <div class="stat"><span class="v" id="sCue">1/6</span><span class="k">cue</span></div>
          <div class="stat"><span class="v" id="sFps">—</span><span class="k">fps</span></div>
        </div>
        <div class="meter">
          <span class="lbl">arrival</span>
          <span class="bar" id="barWrap"><i id="bar"></i></span>
          <span class="num" id="sPct">0%</span>
        </div>
        <span class="pill" id="pill"><span class="dot"></span><span id="pillText">flying</span></span>
        <p class="cap">Longest hop this cue: <b class="mono" id="sHop">—</b> · <span class="mono" id="sNext">—</span></p>
      </section>

      <section class="card" aria-label="Shapes">
        <h2>Shapes</h2>
        <div class="chips" id="chips" role="group" aria-label="Pick a shape">
          <button type="button" data-i="0" aria-pressed="true">Circle</button>
          <button type="button" data-i="1" aria-pressed="false">Star</button>
          <button type="button" data-i="2" aria-pressed="false">Heart</button>
          <button type="button" data-i="3" aria-pressed="false">Spiral</button>
          <button type="button" data-i="4" aria-pressed="false">Grid</button>
          <button type="button" data-i="5" aria-pressed="false" id="wordChip">HELLO</button>
        </div>
        <div class="wordrow">
          <label class="sr-only" for="word">Word for the lights to spell (up to 9 characters)</label>
          <input type="text" id="word" value="HELLO" maxlength="9" spellcheck="false"
                 autocomplete="off" autocapitalize="characters" aria-describedby="wordHelp">
          <button type="button" id="spell">Spell</button>
        </div>
        <p class="cap" id="wordHelp">The word is drawn to a hidden canvas, its outline sampled pixel by pixel, then thinned to exactly 200 spots — each one as far as it can get from the spots already taken.</p>
      </section>

      <section class="card" aria-label="Show controls">
        <h2>Controls</h2>
        <div class="ctl" id="speedCtl">
          <div class="ctl-top">
            <label for="speed">Transition</label><span class="val" id="speedV" aria-hidden="true">1.60 s</span>
          </div>
          <input type="range" id="speed" min="0.4" max="4" step="0.1" value="1.6">
        </div>
        <label class="switch" for="tour" id="tourLabel">
          <input type="checkbox" id="tour" checked>
          <span class="track" aria-hidden="true"></span>
          <span>Auto-play tour</span>
        </label>
        <label class="switch" for="trails" id="trailsLabel">
          <input type="checkbox" id="trails" checked>
          <span class="track" aria-hidden="true"></span>
          <span>Light trails</span>
        </label>
        <div class="row">
          <button type="button" id="next">Next shape</button>
          <button type="button" id="again">Replay cue</button>
        </div>
        <p class="note" id="rmNote" hidden>
          Your system asks for reduced motion, so the show is held as still frames — the lights
          snap straight to each shape and the travel controls are off. <b>Next shape</b> steps
          through the tour by hand, and typing a word still works.
        </p>
      </section>

    </div>
  </main>

  <footer>demo · sloprun.dev</footer>
</div>

<div class="sr-only" role="status" aria-live="polite" id="live"></div>

<script>
(function () {
  "use strict";

  /* ── theme plumbing ─────────────────────────────────────────────────────── */
  var root  = document.documentElement;
  var mqDark = window.matchMedia ? matchMedia("(prefers-color-scheme: dark)") : null;
  var mqRM   = window.matchMedia ? matchMedia("(prefers-reduced-motion: reduce)") : null;
  var reduced = !!(mqRM && mqRM.matches);

  window.addEventListener("message", function (e) {
    var d = e.data;
    if (d && d.type === "sloprun:theme" && (d.theme === "light" || d.theme === "dark")) {
      root.setAttribute("data-theme", d.theme);
      readTheme();
      if (!running) render(performance.now());
    }
  });
  if (mqDark) {
    var onScheme = function () { readTheme(); if (!running) render(performance.now()); };
    if (mqDark.addEventListener) mqDark.addEventListener("change", onScheme);
    else if (mqDark.addListener) mqDark.addListener(onScheme);
  }

  /* ── dom ────────────────────────────────────────────────────────────────── */
  var field = document.getElementById("field");
  var canvas = document.getElementById("c");
  var ctx = canvas.getContext("2d");
  var hint = document.getElementById("hint");
  var mName = document.getElementById("mName");
  var sCue = document.getElementById("sCue");
  var sFps = document.getElementById("sFps");
  var sPct = document.getElementById("sPct");
  var sHop = document.getElementById("sHop");
  var sNext = document.getElementById("sNext");
  var bar = document.getElementById("bar");
  var barWrap = document.getElementById("barWrap");
  var pill = document.getElementById("pill");
  var pillText = document.getElementById("pillText");
  var chipsEl = document.getElementById("chips");
  var chips = [].slice.call(chipsEl.querySelectorAll("button"));
  var wordChip = document.getElementById("wordChip");
  var wordEl = document.getElementById("word");
  var spellBtn = document.getElementById("spell");
  var speedEl = document.getElementById("speed");
  var speedV = document.getElementById("speedV");
  var tourEl = document.getElementById("tour");
  var trailsEl = document.getElementById("trails");
  var nextBtn = document.getElementById("next");
  var againBtn = document.getElementById("again");
  var rmNote = document.getElementById("rmNote");
  var live = document.getElementById("live");

  /* ── colours ────────────────────────────────────────────────────────────── */
  var COL = { dot: "#FFB454", core: "#FFFFFF", top: "#07090D", bot: "#161B25" };
  var GLOW_A = 0.84, TRAIL_A = 0.22, STAR_A = 0.55;
  var sprite = document.createElement("canvas");
  var spriteSize = 96;

  function css(name, fb) {
    var v = getComputedStyle(root).getPropertyValue(name);
    v = v ? v.trim() : "";
    return v || fb;
  }
  function num(name, fb) {
    var v = parseFloat(getComputedStyle(root).getPropertyValue(name));
    return isNaN(v) ? fb : v;
  }
  function hexToRgb(h) {
    h = String(h).trim();
    if (h.charAt(0) === "#") h = h.slice(1);
    if (h.length === 3) h = h.charAt(0)+h.charAt(0)+h.charAt(1)+h.charAt(1)+h.charAt(2)+h.charAt(2);
    var n = parseInt(h, 16);
    if (isNaN(n)) return [255, 180, 84];
    return [(n >> 16) & 255, (n >> 8) & 255, n & 255];
  }
  function rgba(hex, a) {
    var c = hexToRgb(hex);
    return "rgba(" + c[0] + "," + c[1] + "," + c[2] + "," + a + ")";
  }

  function buildSprite() {
    var S = spriteSize;
    sprite.width = S; sprite.height = S;
    var g = sprite.getContext("2d");
    g.clearRect(0, 0, S, S);
    var grd = g.createRadialGradient(S / 2, S / 2, 0, S / 2, S / 2, S / 2);
    grd.addColorStop(0.00, rgba(COL.core, 1));
    grd.addColorStop(0.10, rgba(COL.core, 0.92));
    grd.addColorStop(0.20, rgba(COL.dot, 0.72));
    grd.addColorStop(0.42, rgba(COL.dot, 0.22));
    grd.addColorStop(0.70, rgba(COL.dot, 0.06));
    grd.addColorStop(1.00, rgba(COL.dot, 0));
    g.fillStyle = grd;
    g.fillRect(0, 0, S, S);
  }

  /* The sky + stars are painted once into an offscreen backdrop and blitted
     opaquely every frame. Fading the live canvas towards the sky instead (the
     usual trails trick) leaves permanent 1-2 level burn-in wherever a light has
     ever been, because round(c*(1-a) + sky*a) === c for small c-sky. */
  var bg = document.createElement("canvas");
  function buildSky() {
    if (!W || !H) return;
    bg.width = Math.max(1, Math.round(W * dpr));
    bg.height = Math.max(1, Math.round(H * dpr));
    var g = bg.getContext("2d");
    if (!g) return;
    g.setTransform(dpr, 0, 0, dpr, 0, 0);
    var grd = g.createLinearGradient(0, 0, 0, H);
    grd.addColorStop(0, COL.top);
    grd.addColorStop(1, COL.bot);
    g.globalCompositeOperation = "source-over";
    g.globalAlpha = 1;
    g.fillStyle = grd;
    g.fillRect(0, 0, W, H);
    g.globalCompositeOperation = "lighter";
    for (var i = 0; i < stars.length; i++) {
      var st = stars[i];
      g.globalAlpha = Math.min(1, STAR_A * st.a);
      var sr = st.s * 3.2;
      g.drawImage(sprite, st.x - sr, st.y - sr, sr * 2, sr * 2);
    }
    g.globalAlpha = 1;
    g.globalCompositeOperation = "source-over";
  }

  function readTheme() {
    COL.dot  = css("--dot", COL.dot);
    COL.core = css("--core", COL.core);
    COL.top  = css("--sky-top", COL.top);
    COL.bot  = css("--sky-bot", COL.bot);
    GLOW_A  = num("--glow-a", GLOW_A);
    TRAIL_A = num("--trail-a", TRAIL_A);
    STAR_A  = num("--star-a", STAR_A);
    buildSprite();
    buildSky();
  }

  /* ── geometry helpers ───────────────────────────────────────────────────── */
  var TAU = Math.PI * 2;
  var N = 200;

  /* deterministic little rng so the sky looks the same each load */
  function mulberry(a) {
    return function () {
      a |= 0; a = (a + 0x6D2B79F5) | 0;
      var t = Math.imul(a ^ (a >>> 15), 1 | a);
      t = (t + Math.imul(t ^ (t >>> 7), 61 | t)) ^ t;
      return ((t ^ (t >>> 14)) >>> 0) / 4294967296;
    };
  }

  /* even arc-length resample of a dense polyline */
  function resample(pts, n, closed) {
    var i, seg = [], total = 0;
    var m = pts.length;
    var last = closed ? m : m - 1;
    for (i = 0; i < last; i++) {
      var a = pts[i], b = pts[(i + 1) % m];
      var d = Math.sqrt((b[0]-a[0])*(b[0]-a[0]) + (b[1]-a[1])*(b[1]-a[1]));
      seg.push(d); total += d;
    }
    var out = [], k = 0, acc = 0;
    for (i = 0; i < n; i++) {
      var want = total * (i / n);
      while (k < seg.length - 1 && acc + seg[k] < want) { acc += seg[k]; k++; }
      var t = seg[k] > 0 ? (want - acc) / seg[k] : 0;
      var p = pts[k], q = pts[(k + 1) % m];
      out.push([p[0] + (q[0]-p[0]) * t, p[1] + (q[1]-p[1]) * t]);
    }
    return out;
  }

  function circleShape(n) {
    var out = [], i;
    for (i = 0; i < n; i++) {
      var a = (i / n) * TAU - Math.PI / 2;
      out.push([Math.cos(a), Math.sin(a)]);
    }
    return out;
  }
  function starShape(n) {
    var v = [], i;
    for (i = 0; i < 10; i++) {
      var a = (i / 10) * TAU - Math.PI / 2;
      var r = (i % 2 === 0) ? 1 : 0.42;
      v.push([Math.cos(a) * r, Math.sin(a) * r]);
    }
    var dense = [];
    for (i = 0; i < 10; i++) {
      var p = v[i], q = v[(i + 1) % 10];
      for (var s = 0; s < 24; s++) {
        var t = s / 24;
        dense.push([p[0] + (q[0]-p[0]) * t, p[1] + (q[1]-p[1]) * t]);
      }
    }
    return resample(dense, n, true);
  }
  function heartShape(n) {
    var dense = [], i;
    for (i = 0; i < 720; i++) {
      var t = (i / 720) * TAU;
      var x = 16 * Math.pow(Math.sin(t), 3);
      var y = -(13 * Math.cos(t) - 5 * Math.cos(2*t) - 2 * Math.cos(3*t) - Math.cos(4*t));
      dense.push([x / 17, y / 17]);
    }
    return resample(dense, n, true);
  }
  function spiralShape(n) {
    var dense = [], i;
    for (i = 0; i < 900; i++) {
      var u = i / 899;
      var a = u * TAU * 3.15;
      var r = 0.10 + 0.92 * u;
      dense.push([Math.cos(a) * r, Math.sin(a) * r]);
    }
    return resample(dense, n, false);
  }
  function gridShape(n) {
    var cols = 20, rows = Math.ceil(n / cols);
    var out = [], i;
    for (i = 0; i < n; i++) {
      var cx = i % cols, cy = (i / cols) | 0;
      var x = cols > 1 ? (cx / (cols - 1)) * 2 - 1 : 0;
      var y = rows > 1 ? (cy / (rows - 1)) * 2 - 1 : 0;
      out.push([x * 1.22, y * 0.56]);
    }
    return out;
  }

  /* word → outline sample → exactly n spots */
  var lastWordStats = { cand: 0 };
  function wordShape(word, n) {
    var W0 = 900, H0 = 300;
    var off = document.createElement("canvas");
    off.width = W0; off.height = H0;
    var g = off.getContext("2d");
    if (!g) return null;
    g.fillStyle = "#000"; g.fillRect(0, 0, W0, H0);
    g.fillStyle = "#fff";
    g.textAlign = "center"; g.textBaseline = "middle";
    var FONT = 'system-ui, -apple-system, "Segoe UI", sans-serif';
    var fs = 190;
    g.font = "700 " + fs + "px " + FONT;
    var wpx = g.measureText(word).width;
    if (wpx > W0 - 44 && wpx > 0) {
      fs = Math.max(26, fs * (W0 - 44) / wpx);
      g.font = "700 " + fs + "px " + FONT;
    }
    g.fillText(word, W0 / 2, H0 / 2);

    var data;
    try { data = g.getImageData(0, 0, W0, H0).data; }
    catch (err) { return null; }

    var step = 3;
    function on(x, y) {
      if (x < 0 || y < 0 || x >= W0 || y >= H0) return false;
      return data[(y * W0 + x) * 4] > 128;
    }
    var cand = [], x, y;
    for (y = 0; y < H0; y += step) {
      for (x = 0; x < W0; x += step) {
        if (!on(x, y)) continue;
        if (on(x - step, y) && on(x + step, y) && on(x, y - step) && on(x, y + step)) continue;
        cand.push(x, y);
      }
    }
    var cnt = cand.length / 2;
    lastWordStats.cand = cnt;
    if (cnt === 0) return null;

    /* shuffle candidate order (seeded) */
    var idx = new Int32Array(cnt), i;
    for (i = 0; i < cnt; i++) idx[i] = i;
    var rnd = mulberry(0x5107 + cnt);
    for (i = cnt - 1; i > 0; i--) {
      var j = (rnd() * (i + 1)) | 0;
      var tmp = idx[i]; idx[i] = idx[j]; idx[j] = tmp;
    }

    /* farthest-point sampling — each spot taken is the candidate furthest from
       every spot already taken, so 200 lights land evenly along the outline
       however crowded the word is */
    var accX = [], accY = [];
    var take = Math.min(n, cnt);
    var far = new Float64Array(cnt);
    var seed0 = idx[0];
    accX.push(cand[seed0 * 2]); accY.push(cand[seed0 * 2 + 1]);
    for (i = 0; i < cnt; i++) {
      var fx = cand[i * 2] - accX[0], fy = cand[i * 2 + 1] - accY[0];
      far[i] = fx * fx + fy * fy;
    }
    while (accX.length < take) {
      var pick = -1, pickD = -1;
      for (i = 0; i < cnt; i++) { if (far[i] > pickD) { pickD = far[i]; pick = i; } }
      if (pick < 0 || pickD <= 0) break;
      var nx0 = cand[pick * 2], ny0 = cand[pick * 2 + 1];
      accX.push(nx0); accY.push(ny0);
      for (i = 0; i < cnt; i++) {
        var ex = cand[i * 2] - nx0, ey = cand[i * 2 + 1] - ny0;
        var e2 = ex * ex + ey * ey;
        if (e2 < far[i]) far[i] = e2;
      }
    }
    /* still short (very thin glyphs)? pad from the candidate pool with jitter */
    while (accX.length < n) {
      var kk = idx[accX.length % cnt];
      accX.push(cand[kk * 2] + (rnd() - 0.5) * 4);
      accY.push(cand[kk * 2 + 1] + (rnd() - 0.5) * 4);
    }

    var minX = Infinity, maxX = -Infinity, minY = Infinity, maxY = -Infinity;
    for (i = 0; i < n; i++) {
      if (accX[i] < minX) minX = accX[i];
      if (accX[i] > maxX) maxX = accX[i];
      if (accY[i] < minY) minY = accY[i];
      if (accY[i] > maxY) maxY = accY[i];
    }
    var bw = Math.max(1, maxX - minX), bh = Math.max(1, maxY - minY);
    var sc = Math.min(2.64 / bw, 0.98 / bh);
    var ox0 = (minX + maxX) / 2, oy0 = (minY + maxY) / 2;
    var out = [];
    for (i = 0; i < n; i++) out.push([(accX[i] - ox0) * sc, (accY[i] - oy0) * sc]);
    return out;
  }

  /* ── shape registry ─────────────────────────────────────────────────────── */
  var ORDER = ["circle", "star", "heart", "spiral", "grid", "word"];
  var LABEL = { circle: "Circle", star: "Star", heart: "Heart", spiral: "Spiral", grid: "Grid", word: "" };
  var cache = {};
  var word = "HELLO";

  function shapeFor(name) {
    if (name === "word") {
      if (cache.word && cache.wordKey === word) return cache.word;
      var pts = wordShape(word, N);
      if (!pts) return null;
      cache.word = pts; cache.wordKey = word;
      return pts;
    }
    if (cache[name]) return cache[name];
    var made =
      name === "circle" ? circleShape(N) :
      name === "star"   ? starShape(N) :
      name === "heart"  ? heartShape(N) :
      name === "spiral" ? spiralShape(N) :
                          gridShape(N);
    cache[name] = made;
    return made;
  }

  /* ── canvas sizing ──────────────────────────────────────────────────────── */
  var W = 0, H = 0, dpr = 1, U = 1, CX = 0, CY = 0, stars = [];

  function mapx(nx) { return CX + nx * U; }
  function mapy(ny) { return CY + ny * U; }

  function resize() {
    var r = field.getBoundingClientRect();
    var w = Math.max(160, Math.round(r.width));
    var h = Math.max(140, Math.round(r.height));
    dpr = Math.min(2, window.devicePixelRatio || 1);
    if (canvas.width !== Math.round(w * dpr) || canvas.height !== Math.round(h * dpr)) {
      canvas.width = Math.round(w * dpr);
      canvas.height = Math.round(h * dpr);
    }
    var oldU = U, oldCX = CX, oldCY = CY, had = W > 0;
    W = w; H = h;
    var pad = Math.max(14, Math.min(w, h) * 0.05);
    U = Math.max(24, Math.min((w / 2 - pad) / 1.36, (h / 2 - pad) / 1.04));
    CX = w / 2; CY = h / 2;

    if (had && oldU > 0) {
      var k = U / oldU;
      for (var i = 0; i < N; i++) {
        px[i] = CX + (px[i] - oldCX) * k;  py[i] = CY + (py[i] - oldCY) * k;
        sxA[i] = CX + (sxA[i] - oldCX) * k; syA[i] = CY + (syA[i] - oldCY) * k;
        bxA[i] = CX + (bxA[i] - oldCX) * k; byA[i] = CY + (byA[i] - oldCY) * k;
        for (var t2 = 0; t2 < TAIL; t2++) {
          hxA[i * TAIL + t2] = CX + (hxA[i * TAIL + t2] - oldCX) * k;
          hyA[i * TAIL + t2] = CY + (hyA[i * TAIL + t2] - oldCY) * k;
        }
      }
    }
    remapGoals();

    /* seeded stars */
    stars.length = 0;
    var rnd = mulberry(1337);
    var count = Math.round((w * h) / 5200);
    for (var s = 0; s < count; s++) {
      stars.push({ x: rnd() * w, y: rnd() * h * 0.82, s: 0.5 + rnd() * 1.1, a: 0.25 + rnd() * 0.75 });
    }
    buildSky();
  }

  /* ── the lights ─────────────────────────────────────────────────────────── */
  var px = new Float32Array(N), py = new Float32Array(N);
  var bxA = new Float32Array(N), byA = new Float32Array(N);
  var sxA = new Float32Array(N), syA = new Float32Array(N);
  var gxA = new Float32Array(N), gyA = new Float32Array(N);
  var ox = new Float32Array(N), oy = new Float32Array(N);
  var ovx = new Float32Array(N), ovy = new Float32Array(N);
  var nfx = new Float32Array(N), nfy = new Float32Array(N);
  var pfx = new Float32Array(N), pfy = new Float32Array(N);
  var sepS = new Float32Array(N);
  var phase = new Float32Array(N), twk = new Float32Array(N);
  var amp = new Float32Array(N), sizeF = new Float32Array(N), delay = new Float32Array(N);
  var slot = new Int32Array(N);          /* slot[i] = index into the current shape */
  var curShape = circleShape(N);

  /* short ring of past positions per light — the tails are drawn from these,
     so the sky itself is never smeared and never burns in */
  var TAIL = 6;
  var TAILW = [0, 0.52, 0.34, 0.22, 0.13, 0.07];
  var hxA = new Float32Array(N * TAIL), hyA = new Float32Array(N * TAIL);
  var hHead = 0;
  function resetTail() {
    for (var i = 0; i < N; i++) {
      for (var k = 0; k < TAIL; k++) { hxA[i * TAIL + k] = px[i]; hyA[i * TAIL + k] = py[i]; }
    }
  }
  function pushTail() {
    hHead = (hHead + 1) % TAIL;
    for (var i = 0; i < N; i++) { hxA[i * TAIL + hHead] = px[i]; hyA[i * TAIL + hHead] = py[i]; }
  }

  (function seedDots() {
    var rnd = mulberry(9001);
    for (var i = 0; i < N; i++) {
      phase[i] = rnd() * TAU;
      twk[i] = 0.55 + rnd() * 0.9;
      amp[i] = 0.7 + rnd() * 1.5;
      sizeF[i] = 0.82 + rnd() * 0.45;
      delay[i] = rnd();
      slot[i] = i;
    }
  })();

  function remapGoals() {
    for (var i = 0; i < N; i++) {
      var p = curShape[slot[i]];
      gxA[i] = mapx(p[0]); gyA[i] = mapy(p[1]);
    }
  }

  /* pair each light with a spot: angular order first (paths fan out instead of
     crossing), then a few thousand swap trials to shave the total distance. */
  var longestHop = 0;
  function assign(shape) {
    var i;
    var c1x = 0, c1y = 0, c2x = 0, c2y = 0;
    for (i = 0; i < N; i++) { c1x += px[i]; c1y += py[i]; }
    c1x /= N; c1y /= N;
    for (i = 0; i < N; i++) { c2x += shape[i][0]; c2y += shape[i][1]; }
    c2x /= N; c2y /= N;

    var a1 = [], a2 = [];
    for (i = 0; i < N; i++) {
      a1.push([Math.atan2(py[i] - c1y, px[i] - c1x), i]);
      a2.push([Math.atan2(shape[i][1] - c2y, shape[i][0] - c2x), i]);
    }
    a1.sort(function (a, b) { return a[0] - b[0]; });
    a2.sort(function (a, b) { return a[0] - b[0]; });
    for (i = 0; i < N; i++) slot[a1[i][1]] = a2[i][1];

    curShape = shape;
    remapGoals();

    /* swap refinement */
    var rnd = mulberry(4242);
    function cost(i) {
      var dx = gxA[i] - px[i], dy = gyA[i] - py[i];
      return dx * dx + dy * dy;
    }
    for (var k = 0; k < 9000; k++) {
      var i1 = (rnd() * N) | 0, i2 = (rnd() * N) | 0;
      if (i1 === i2) continue;
      var before = cost(i1) + cost(i2);
      var tx = gxA[i1], ty = gyA[i1];
      gxA[i1] = gxA[i2]; gyA[i1] = gyA[i2];
      gxA[i2] = tx; gyA[i2] = ty;
      var after = cost(i1) + cost(i2);
      if (after < before) {
        var ts = slot[i1]; slot[i1] = slot[i2]; slot[i2] = ts;
      } else {
        gxA[i2] = gxA[i1]; gyA[i2] = gyA[i1];
        gxA[i1] = tx; gyA[i1] = ty;
      }
    }
    longestHop = 0;
    for (i = 0; i < N; i++) {
      var d = Math.sqrt(cost(i));
      if (d > longestHop) longestHop = d;
    }
  }

  /* ── show state ─────────────────────────────────────────────────────────── */
  var cue = 0;
  var durMs = 1600;
  var curDur = 1600;            /* duration locked in when the cue started */
  var DF = 0.34;                 /* share of the transition spent staggering starts */
  var HOLD = 2900;
  var transiting = false, tStart = 0, holdUntil = 0, progAll = 1;
  var trails = true, tour = true;
  var running = false, raf = 0, last = 0, fps = 0, lastUi = 0;
  var pointer = { on: false, x: 0, y: 0 };

  function ease(t) { return t < 0.5 ? 4 * t * t * t : 1 - Math.pow(-2 * t + 2, 3) / 2; }

  function goTo(idx, opts) {
    var name = ORDER[idx];
    var shape = shapeFor(name);
    if (!shape) { say("That word left nothing to draw — try letters or digits."); return false; }
    cue = idx;
    assign(shape);
    if (reduced) {
      for (var i = 0; i < N; i++) {
        px[i] = gxA[i]; py[i] = gyA[i];
        bxA[i] = gxA[i]; byA[i] = gyA[i];
        ox[i] = oy[i] = ovx[i] = ovy[i] = 0;
      }
      transiting = false; progAll = 1;
      render(performance.now());
    } else {
      /* start from the eased BASE, not the drawn position: px already carries
         ox/oy + bob, and update() re-adds them, so seeding from px made every
         light pop by that offset the instant a cue started. */
      for (var j = 0; j < N; j++) { sxA[j] = bxA[j]; syA[j] = byA[j]; }
      curDur = durMs;
      tStart = performance.now();
      transiting = true; progAll = 0;
    }
    syncChips();
    syncReadout(performance.now());
    if (!opts || !opts.silent) say("Shape: " + shapeLabel(idx));
    return true;
  }

  function shapeLabel(idx) {
    var n = ORDER[idx];
    return n === "word" ? ('the word "' + word + '"') : LABEL[n];
  }

  function nextCue(silent) { goTo((cue + 1) % ORDER.length, silent ? { silent: true } : null); }

  /* ── update ─────────────────────────────────────────────────────────────── */
  function update(now, dt) {
    var i, t = now / 1000;

    if (transiting) {
      var e = now - tStart;
      var span = curDur * (1 - DF);
      var sum = 0;
      for (i = 0; i < N; i++) {
        var p = (e - delay[i] * curDur * DF) / span;
        p = p < 0 ? 0 : (p > 1 ? 1 : p);
        var q = ease(p);
        bxA[i] = sxA[i] + (gxA[i] - sxA[i]) * q;
        byA[i] = syA[i] + (gyA[i] - syA[i]) * q;
        sepS[i] = Math.sin(Math.PI * p);
        sum += p;
      }
      progAll = sum / N;
      if (e >= curDur) {
        transiting = false; progAll = 1;
        for (i = 0; i < N; i++) { bxA[i] = gxA[i]; byA[i] = gyA[i]; sepS[i] = 0; }
        holdUntil = now + HOLD;
        setPill(true);
      }
    } else {
      for (i = 0; i < N; i++) { bxA[i] = gxA[i]; byA[i] = gyA[i]; sepS[i] = 0; }
      /* the tour runs itself — announcing every cue would interrupt a screen
         reader forever, so only the visitor's own actions speak */
      if (tour && now >= holdUntil) { holdUntil = now + HOLD; nextCue(true); }
    }

    /* neighbour separation — only bites mid-flight, so shapes stay exact */
    var R = Math.max(8, U * 0.055), R2 = R * R;
    for (i = 0; i < N; i++) { nfx[i] = 0; nfy[i] = 0; pfx[i] = 0; pfy[i] = 0; }
    if (transiting) {
      for (i = 0; i < N; i++) {
        for (var j = i + 1; j < N; j++) {
          var dx = px[i] - px[j], dy = py[i] - py[j];
          var d2 = dx * dx + dy * dy;
          if (d2 >= R2 || d2 < 1e-6) continue;
          var d = Math.sqrt(d2);
          var f = (1 - d / R) / d;
          nfx[i] += dx * f; nfy[i] += dy * f;
          nfx[j] -= dx * f; nfy[j] -= dy * f;
        }
      }
    }
    if (pointer.on) {
      var PR = Math.max(40, U * 0.36), PR2 = PR * PR;
      for (i = 0; i < N; i++) {
        var ddx = px[i] - pointer.x, ddy = py[i] - pointer.y;
        var dd2 = ddx * ddx + ddy * ddy;
        if (dd2 >= PR2 || dd2 < 1e-6) continue;
        var dd = Math.sqrt(dd2);
        var pf = (1 - dd / PR) / dd;
        pfx[i] += ddx * pf; pfy[i] += ddy * pf;
      }
    }

    var NK = R * 30, PK = R * 26;
    var damp = Math.exp(-dt * 3.2);
    var leak = Math.min(1, dt * 3);
    var lim = R * 3;
    for (i = 0; i < N; i++) {
      var ax = nfx[i] * NK * sepS[i] + pfx[i] * PK;
      var ay = nfy[i] * NK * sepS[i] + pfy[i] * PK;
      ovx[i] = (ovx[i] + ax * dt) * damp;
      ovy[i] = (ovy[i] + ay * dt) * damp;
      ox[i] += ovx[i] * dt; ox[i] -= ox[i] * leak;
      oy[i] += ovy[i] * dt; oy[i] -= oy[i] * leak;
      if (ox[i] > lim) ox[i] = lim; else if (ox[i] < -lim) ox[i] = -lim;
      if (oy[i] > lim) oy[i] = lim; else if (oy[i] < -lim) oy[i] = -lim;

      var bobx = Math.sin(t * twk[i] * 0.7 + phase[i]) * amp[i];
      var boby = Math.cos(t * twk[i] * 0.52 + phase[i] * 1.7) * amp[i] * 0.8;
      px[i] = bxA[i] + ox[i] + bobx;
      py[i] = byA[i] + oy[i] + boby;
    }
  }

  /* ── render ─────────────────────────────────────────────────────────────── */
  function render(now) {
    if (!W || !H) return;
    var t = now / 1000, i;
    ctx.setTransform(dpr, 0, 0, dpr, 0, 0);

    ctx.globalCompositeOperation = "source-over";
    ctx.globalAlpha = 1;
    if (bg.width > 1) ctx.drawImage(bg, 0, 0, W, H);
    else { ctx.fillStyle = COL.top; ctx.fillRect(0, 0, W, H); }

    ctx.globalCompositeOperation = "lighter";
    var tails = trails && !reduced;
    var base = Math.max(3.4, Math.min(11, U * 0.038));
    for (i = 0; i < N; i++) {
      var tw = 0.62 + 0.28 * Math.sin(t * twk[i] * 1.35 + phase[i]);
      var b = reduced ? 0.85 : Math.min(1.05, tw + 0.3 * sepS[i]);
      var r = base * sizeF[i] * (0.86 + 0.34 * b);
      if (tails) {
        for (var k = TAIL - 1; k >= 1; k--) {
          var s = (hHead - k + TAIL) % TAIL;
          var hx = hxA[i * TAIL + s], hy = hyA[i * TAIL + s];
          ctx.globalAlpha = Math.min(1, GLOW_A * b * TRAIL_A * TAILW[k]);
          var rr = r * (1 - 0.1 * k);
          ctx.drawImage(sprite, hx - rr, hy - rr, rr * 2, rr * 2);
        }
      }
      ctx.globalAlpha = Math.min(1, GLOW_A * b * 1.32);
      ctx.drawImage(sprite, px[i] - r, py[i] - r, r * 2, r * 2);
    }

    ctx.globalAlpha = 1;
    ctx.globalCompositeOperation = "source-over";
  }

  /* ── loop ───────────────────────────────────────────────────────────────── */
  function step(now) {
    raf = requestAnimationFrame(step);
    var dt = (now - last) / 1000;
    last = now;
    if (!(dt > 0) || dt > 0.05) dt = 0.0166;
    fps = fps ? fps * 0.9 + (1 / dt) * 0.1 : 1 / dt;
    update(now, dt);
    pushTail();
    render(now);
    if (now - lastUi > 100) { lastUi = now; syncReadout(now); }
  }
  function start() {
    if (running || reduced) return;
    running = true; last = performance.now(); raf = requestAnimationFrame(step);
  }
  function stop() {
    running = false;
    if (raf) cancelAnimationFrame(raf);
    raf = 0;
  }

  /* ── readout ────────────────────────────────────────────────────────────── */
  function setPill(ok) {
    if (ok) { pill.classList.add("on"); pillText.textContent = "in place"; }
    else { pill.classList.remove("on"); pillText.textContent = "flying"; }
  }

  function syncReadout(now) {
    var pct = Math.round(progAll * 100);
    bar.style.width = pct + "%";
    sPct.textContent = pct + "%";
    if (pct >= 100) barWrap.classList.add("done"); else barWrap.classList.remove("done");
    sCue.textContent = (cue + 1) + "/" + ORDER.length;
    sFps.textContent = reduced ? "—" : String(Math.round(fps));
    sHop.textContent = reduced ? "—" : (Math.round(longestHop) + " px");
    var label = ORDER[cue] === "word" ? '"' + word + '"' : LABEL[ORDER[cue]];
    mName.textContent = label;
    setPill(!transiting);
    if (reduced) {
      sNext.textContent = "held · step by hand";
    } else if (transiting) {
      sNext.textContent = "arriving";
    } else if (tour) {
      var left = Math.max(0, (holdUntil - now) / 1000);
      sNext.textContent = "next in " + left.toFixed(1) + "s";
    } else {
      sNext.textContent = "tour off";
    }
  }

  function syncChips() {
    for (var i = 0; i < chips.length; i++) {
      chips[i].setAttribute("aria-pressed", (i === cue) ? "true" : "false");
    }
  }

  var sayTimer = 0;
  function say(msg) {
    clearTimeout(sayTimer);
    sayTimer = setTimeout(function () { live.textContent = msg; }, 120);
  }

  /* ── controls ───────────────────────────────────────────────────────────── */
  chipsEl.addEventListener("click", function (e) {
    var b = e.target.closest ? e.target.closest("button[data-i]") : null;
    if (!b) return;
    goTo(parseInt(b.getAttribute("data-i"), 10));
    holdUntil = performance.now() + durMs + HOLD;
  });

  function applyWord() {
    var v = wordEl.value.replace(/\s+/g, " ").trim().toUpperCase();
    if (!v) { say("Type a word first."); return; }
    wordEl.value = v;
    word = v;
    wordChip.textContent = v;
    cache.word = null; cache.wordKey = null;
    var ok = goTo(5);
    if (ok) {
      say('The lights are spelling "' + v + '" — ' + lastWordStats.cand + " outline samples thinned to 200 spots.");
      holdUntil = performance.now() + durMs + HOLD;
    }
  }
  spellBtn.addEventListener("click", applyWord);
  wordEl.addEventListener("keydown", function (e) {
    if (e.key === "Enter") { e.preventDefault(); applyWord(); }
  });
  wordEl.addEventListener("input", function () {
    spellBtn.disabled = !wordEl.value.trim();
  });

  speedEl.addEventListener("input", function () {
    durMs = parseFloat(speedEl.value) * 1000;
    speedV.textContent = (durMs / 1000).toFixed(2) + " s";
  });

  tourEl.addEventListener("change", function () {
    tour = tourEl.checked;
    if (tour) holdUntil = performance.now() + HOLD;
    syncReadout(performance.now());
    say(tour ? "Auto tour on." : "Auto tour off — pick shapes yourself.");
  });

  trailsEl.addEventListener("change", function () {
    trails = trailsEl.checked;
    say(trails ? "Light trails on." : "Light trails off.");
  });

  nextBtn.addEventListener("click", function () {
    nextCue();
    holdUntil = performance.now() + durMs + HOLD;
  });

  againBtn.addEventListener("click", function () {
    /* scatter, then fly back into the same shape */
    var rnd = mulberry((performance.now() | 0) & 0xffff);
    for (var i = 0; i < N; i++) {
      var a = rnd() * TAU, r = U * (0.15 + rnd() * 1.05);
      px[i] = CX + Math.cos(a) * r;
      py[i] = CY + Math.sin(a) * r * 0.72;
      bxA[i] = px[i]; byA[i] = py[i];
      ox[i] = oy[i] = ovx[i] = ovy[i] = 0;
    }
    resetTail();
    goTo(cue, { silent: true });
    say("Replaying " + shapeLabel(cue) + ".");
    holdUntil = performance.now() + durMs + HOLD;
  });

  /* pointer parting */
  function ptr(e) {
    var r = canvas.getBoundingClientRect();
    pointer.x = e.clientX - r.left;
    pointer.y = e.clientY - r.top;
    pointer.on = true;
    dismissHint();
  }
  if (!reduced) {
    canvas.addEventListener("pointermove", function (e) {
      if (e.pointerType === "touch") return;
      ptr(e);
    });
    canvas.addEventListener("pointerleave", function () { pointer.on = false; });
  }

  /* only a definitively touch-only pointer loses the "part the lights" hint */
  var touchOnly = !!(window.matchMedia && matchMedia("(hover: none) and (pointer: coarse)").matches);
  var hintTimer = 0;
  function dismissHint() {
    if (hint.hidden || hint.classList.contains("gone")) return;
    hint.classList.add("gone");
    clearTimeout(hintTimer);
    setTimeout(function () { hint.hidden = true; }, 500);
  }

  /* ── lifecycle ──────────────────────────────────────────────────────────── */
  document.addEventListener("visibilitychange", function () {
    if (document.hidden) { stop(); }
    else if (!reduced) {
      /* don't let the hold timer fire a pile of cues while hidden */
      holdUntil = performance.now() + HOLD;
      if (transiting) tStart = performance.now() - curDur;
      resetTail();   /* no phantom streak from wherever the lights were when we paused */
      start();
    }
  });

  if (window.ResizeObserver) {
    new ResizeObserver(function () { resize(); if (!running) render(performance.now()); }).observe(field);
  } else {
    window.addEventListener("resize", function () { resize(); if (!running) render(performance.now()); });
  }

  /* ── motion mode ────────────────────────────────────────────────────────── */
  var tourLabel = document.getElementById("tourLabel");
  var trailsLabel = document.getElementById("trailsLabel");
  var speedCtl = document.getElementById("speedCtl");
  var ledeTour = document.getElementById("ledeTour");
  var LEDE_MOVE = ledeTour ? ledeTour.textContent : "";
  var LEDE_STILL = "Your system asks for reduced motion, so the show is held as still frames \u2014 step it with Next shape.";

  function applyMotionUI() {
    rmNote.hidden = !reduced;
    tourEl.disabled = trailsEl.disabled = speedEl.disabled = reduced;
    tourLabel.classList.toggle("off", reduced);
    trailsLabel.classList.toggle("off", reduced);
    speedCtl.classList.toggle("off", reduced);
    nextBtn.classList.toggle("primary", reduced);
    againBtn.hidden = reduced;
    if (reduced) {
      tourEl.checked = false; trailsEl.checked = false;
      tour = false; trails = false;
      pointer.on = false;
      clearTimeout(hintTimer);
      hint.hidden = true;
    } else {
      tourEl.checked = true; trailsEl.checked = true;
      tour = true; trails = true;
    }
    if (ledeTour) ledeTour.textContent = reduced ? LEDE_STILL : LEDE_MOVE;
  }

  /* ── boot ───────────────────────────────────────────────────────────────── */
  readTheme();
  resize();

  /* opening: lights lift off from the grass and rise into the first shape */
  (function liftOff() {
    var rnd = mulberry(77);
    for (var i = 0; i < N; i++) {
      px[i] = CX + (rnd() - 0.5) * W * 0.88;
      py[i] = H * 0.84 + rnd() * H * 0.13;
      bxA[i] = px[i]; byA[i] = py[i];
    }
    resetTail();
  })();

  durMs = parseFloat(speedEl.value) * 1000;
  speedV.textContent = (durMs / 1000).toFixed(2) + " s";
  trails = trailsEl.checked;
  tour = tourEl.checked;

  if (reduced) {
    applyMotionUI();
    goTo(0, { silent: true });
    syncReadout(performance.now());
  } else {
    applyMotionUI();
    var opening = durMs;
    durMs = Math.max(2200, durMs * 1.6);
    goTo(0, { silent: true });
    durMs = opening;
    holdUntil = performance.now() + 2600 + HOLD;
    syncReadout(performance.now());
    if (touchOnly) hint.hidden = true;
    render(performance.now());   /* paint frame 0 now, don't wait on rAF */
    start();
    hintTimer = setTimeout(dismissHint, 9000);
  }

  /* the OS motion preference can flip while the page is open — honour it live,
     the same way the colour scheme already is */
  if (mqRM) {
    var onMotion = function (e) {
      var want = !!(e && "matches" in e ? e.matches : mqRM.matches);
      if (want === reduced) return;
      reduced = want;
      applyMotionUI();
      if (reduced) {
        stop();
        goTo(cue, { silent: true });
      } else {
        holdUntil = performance.now() + HOLD;
        last = performance.now();
        goTo(cue, { silent: true });
        start();
      }
      syncReadout(performance.now());
    };
    if (mqRM.addEventListener) mqRM.addEventListener("change", onMotion);
    else if (mqRM.addListener) mqRM.addListener(onMotion);
  }
})();
</script>
</body>
</html>