Custom Code Experiment •
Irish Dancing
Source Code View HTML / CSS / JavaScript
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1, viewport-fit=cover">
<title>Glitch Irish dance loader</title>
<style>
:root {
box-sizing: border-box;
padding-top: env(safe-area-inset-top, 0px);
padding-bottom: env(safe-area-inset-bottom, 0px);
--page: #EDEDED;
--ring-track: rgba(0, 0, 0, 0.12);
--accent: #FFC21A;
--void: #0A0A0A;
}
@media (prefers-color-scheme: dark) {
:root:not([data-theme="light"]) {
--page: #141414;
--ring-track: rgba(255, 255, 255, 0.12);
}
}
:root[data-theme="dark"] {
--page: #141414;
--ring-track: rgba(255, 255, 255, 0.12);
}
*, *::before, *::after { box-sizing: inherit; }
html { height: 100%; scroll-padding-top: env(safe-area-inset-top, 0px); }
body {
margin: 0;
height: 100%;
background: var(--page);
display: grid;
place-items: center;
}
.orb {
position: relative;
width: min(260px, 70vw);
aspect-ratio: 1;
}
/* Animated yellow ring */
.ring {
position: absolute;
inset: 0;
width: 100%;
height: 100%;
transform: rotate(-90deg);
}
.ring circle { fill: none; stroke-width: 3; }
.ring .track { stroke: var(--ring-track); }
.ring .arc {
stroke: var(--accent);
stroke-linecap: round;
stroke-dasharray: 90 400;
animation: sweep 1.6s cubic-bezier(.6,.1,.3,.9) infinite;
transform-origin: 50% 50%;
}
@keyframes sweep {
0% { stroke-dasharray: 20 400; transform: rotate(0deg); }
50% { stroke-dasharray: 160 400; }
100% { stroke-dasharray: 20 400; transform: rotate(360deg); }
}
/* Circular viewport */
.window {
position: absolute;
inset: 12px;
border-radius: 50%;
overflow: hidden;
background: radial-gradient(circle at 50% 40%, #262626 0%, var(--void) 70%);
box-shadow: inset 0 0 40px rgba(0,0,0,.8), inset 0 0 0 1px rgba(255,255,255,.2);
}
.window canvas { display: block; width: 100%; height: 100%; }
/* spotlight from above */
.window::before {
content: "";
position: absolute;
inset: 0;
background: radial-gradient(ellipse 38% 70% at 50% 0%, rgba(255,255,255,.09), transparent 70%);
pointer-events: none;
}
/* scanlines */
.window::after {
content: "";
position: absolute;
inset: 0;
background: repeating-linear-gradient(to bottom, rgba(0,0,0,0) 0 2px, rgba(0,0,0,.28) 2px 3px);
pointer-events: none;
}
@media (prefers-reduced-motion: reduce) {
.ring .arc { animation-duration: 4s; }
}
</style>
</head>
<body>
<div class="orb" role="status" aria-label="Loading">
<svg class="ring" viewBox="0 0 100 100" aria-hidden="true">
<circle class="track" cx="50" cy="50" r="48"/>
<circle class="arc" cx="50" cy="50" r="48"/>
</svg>
<div class="window">
<canvas id="dancer" aria-hidden="true"></canvas>
</div>
</div>
<script>
(() => {
const canvas = document.getElementById('dancer');
const ctx = canvas.getContext('2d');
const buf = document.createElement('canvas');
const bctx = buf.getContext('2d');
const reduced = window.matchMedia('(prefers-reduced-motion: reduce)').matches;
const WHITE = '#FFFFFF';
const FLOOR = '#8C8C8C';
const GHOST_A = '#8C8C8C', GHOST_B = '#E0E0E0';
let W = 0, H = 0, dpr = 1;
function resize() {
dpr = Math.min(window.devicePixelRatio || 1, 2);
const r = canvas.getBoundingClientRect();
W = Math.round(r.width * dpr); H = Math.round(r.height * dpr);
canvas.width = buf.width = W;
canvas.height = buf.height = H;
}
new ResizeObserver(resize).observe(canvas);
resize();
// ---------- Vector helpers ----------
const add = (a, b) => [a[0]+b[0], a[1]+b[1], a[2]+b[2]];
const mul = (a, k) => [a[0]*k, a[1]*k, a[2]*k];
const rotX = ([x, y, z], a) => [x, y*Math.cos(a) - z*Math.sin(a), y*Math.sin(a) + z*Math.cos(a)];
const rotY = ([x, y, z], a) => [x*Math.cos(a) + z*Math.sin(a), y, -x*Math.sin(a) + z*Math.cos(a)];
const rotZ = ([x, y, z], a) => [x*Math.cos(a) - y*Math.sin(a), x*Math.sin(a) + y*Math.cos(a), z];
// Limb direction: starts pointing down, raised sideways by `abd`, swung forward (+z) by `fwd`
const limbDir = (side, abd, fwd) => rotX(rotZ([0, -1, 0], side * abd), -fwd);
// ---------- Skeleton ----------
const SPINE = 0.72, NECK = 0.1, HEAD_R = 0.17;
const UPPER_ARM = 0.36, FOREARM = 0.34;
const THIGH = 0.44, SHIN = 0.44;
const FLOOR_Y = -1.0;
// ---------- Irish dance steps ----------
// Upper body stays rigid with arms straight down; all the action is in the feet.
const s = Math.sin, c = Math.cos, PI = Math.PI, TAU = PI * 2;
const alt = (b) => (Math.floor(b) % 2 === 0 ? 1 : -1);
const P = (o) => Object.assign({ leanSide: 0, leanFwd: -0.04, headTilt: 0, pitch: 0, roll: 0, spin: 0, yaw: 0, air: 0, tx: 0, tz: 0 }, o);
const ARMS = { abd: 0.07, fwd: 0, eAbd: 0, eFwd: 0 }; // arms locked at the sides
// ---------- Gravity ----------
// The figure is about 2 units tall (~1.7 m), so 1 unit ≈ 0.83 m and g ≈ 11.8 units/s².
const BPM = 118;
const G = 9.81 / 0.83;
const secPerBeat = () => 60 / (reduced ? BPM / 3 : BPM);
// One jump cycle of `period` beats: ground contact centred on the beat, a ballistic
// flight in the middle. Flight time follows from the jump height (t = √(8h/g)), and the
// height follows a true parabola, so the body accelerates down and lands hard.
function jump(b, period, height) {
const flight = Math.min(period * 0.75, Math.sqrt(8 * height / G) / secPerBeat());
const ground = period - flight;
const ph = ((b % period) + period) % period;
const takeoff = ground / 2, landing = takeoff + flight;
if (ph >= takeoff && ph <= landing) {
const u = (ph - takeoff) / flight;
return { air: 4 * height * u * (1 - u), u, flying: true, crouch: 0 };
}
// on the ground: bend on landing to absorb it, press down again to take off
const g = ph < takeoff ? ph + ground / 2 : ph - landing;
return { air: 0, u: 0, flying: false, crouch: s(PI * g / ground) };
}
const soften = (L, cr) => ({ ...L, fwd: L.fwd + 0.25 * cr, knee: L.knee + 0.55 * cr });
// Sevens: travelling sideways with crossed feet, a small hop and a heel flick behind on each beat
const sevens = (b) => {
const a = alt(b), j = jump(b, 1, 0.05);
const k = j.flying ? s(PI * j.u) : 0;
const lift = soften({ abd: -0.12, fwd: -0.45 * k, knee: 2.0 * k, toe: 0.6 + 0.4 * k }, j.crouch);
const stand = soften({ abd: 0.04, fwd: 0, knee: 0, toe: 0.6 }, j.crouch);
return P({
armR: ARMS, armL: ARMS,
legR: a > 0 ? lift : stand, legL: a > 0 ? stand : lift,
air: j.air, tx: 0.32 * s(b * TAU / 8), yaw: 0.25 * c(b * TAU / 8)
});
};
// High kicks: a straight leg kicked up in front while hopping on the other foot
const kicks = (b) => {
const a = alt(b), j = jump(b, 1, 0.07);
const k = s(PI * (((b % 1) + 1) % 1)); // kick peaks mid-hop, back down for the landing
const kick = soften({ abd: 0.02, fwd: 1.75 * k, knee: 0.15 * (1 - k), toe: 0.6 + 0.4 * k }, j.crouch * (1 - k));
const stand = soften({ abd: 0.04, fwd: 0, knee: 0, toe: 0.6 }, j.crouch);
return P({
armR: ARMS, armL: ARMS,
legR: a > 0 ? kick : stand, legL: a > 0 ? stand : kick,
air: j.air, leanFwd: -0.04 - 0.06 * k
});
};
// Leaps: split jumps; the legs open fast after take-off and close before landing
const leaps = (b) => {
const j = jump(b, 2, 0.42);
const sp = j.flying ? Math.min(1, s(PI * j.u) * 1.6) : 0;
const lead = Math.floor(b / 2) % 2 === 0 ? 1 : -1;
const front = soften({ abd: 0.03, fwd: 1.25 * sp, knee: 0.1 * sp, toe: 0.6 + 0.4 * sp }, j.crouch);
const back = soften({ abd: 0.03, fwd: -0.95 * sp, knee: 0.35 * sp, toe: 0.6 + 0.4 * sp }, j.crouch);
return P({
armR: ARMS, armL: ARMS,
legR: lead > 0 ? front : back, legL: lead > 0 ? back : front,
air: j.air, tz: 0.18 * s(b * TAU / 8), yaw: lead * 0.2
});
};
// Heel clicks: jump and knock the heels together out to one side at the top of the jump
const clicks = (b) => {
const j = jump(b, 2, 0.36);
const arc = j.flying ? s(PI * j.u) : 0;
const side = Math.floor(b / 2) % 2 === 0 ? 1 : -1, out = 0.55 * arc;
return P({
armR: ARMS, armL: ARMS,
legR: soften({ abd: side * out + 0.04, fwd: 0.05, knee: 0.25 * arc, toe: 0.6 + 0.4 * arc }, j.crouch),
legL: soften({ abd: -side * out + 0.04, fwd: 0.05, knee: 0.25 * arc, toe: 0.6 + 0.4 * arc }, j.crouch),
air: j.air, leanSide: -side * 0.1 * arc, tx: -side * 0.08 * arc
});
};
const SCHEDULE = [[sevens, 8], [kicks, 8], [leaps, 8], [clicks, 8]];
const TOTAL = SCHEDULE.reduce((n, [, len]) => n + len, 0);
function blend(a, b, w) {
if (typeof a === 'number') return a + (b - a) * w;
const o = {};
for (const k in a) o[k] = blend(a[k], b[k], w);
return o;
}
// Short crossfade that ends on the beat, when both steps have their feet on the floor
const FADE = 0.4;
function poseAt(beat) {
let m = ((beat % TOTAL) + TOTAL) % TOTAL, i = 0;
while (m >= SCHEDULE[i][1]) { m -= SCHEDULE[i][1]; i++; }
const [fn, len] = SCHEDULE[i];
const cur = fn(m, len);
if (m > len - FADE) {
const [nfn, nlen] = SCHEDULE[(i + 1) % SCHEDULE.length];
const next = nfn(m - len, nlen);
let w = (m - (len - FADE)) / FADE;
w = w * w * (3 - 2 * w);
return blend(cur, next, w);
}
return cur;
}
// Build line segments for the figure; lowest point rests on the floor, then lift by `air`
function buildFigure(pose) {
const hipR = [0.07, 0, 0], hipL = [-0.07, 0, 0];
const leg = (hip, side, L) => {
const knee = add(hip, mul(limbDir(side, L.abd, L.fwd), THIGH));
const shinDir = limbDir(side, L.abd * 0.6, L.fwd - L.knee);
const foot = add(knee, mul(shinDir, SHIN));
// turned-out foot, flat on the floor or pointed along the shin
const flat = rotY([0, 0, 0.12], side * 0.45);
const toeTip = add(foot, add(mul(flat, 1 - L.toe), mul(shinDir, 0.12 * L.toe)));
return [hip, knee, foot, toeTip];
};
const lr = leg(hipR, 1, pose.legR), ll = leg(hipL, -1, pose.legL);
const up = rotZ(rotX([0, 1, 0], pose.leanFwd), -pose.leanSide);
const neck = mul(up, SPINE);
const shoulder = mul(up, SPINE - 0.06);
const headC = add(neck, mul(rotZ(up, -pose.headTilt), NECK + HEAD_R));
const arm = (side, A) => {
const d1 = rotZ(limbDir(side, A.abd, A.fwd), -pose.leanSide);
const elbow = add(shoulder, mul(d1, UPPER_ARM));
const d2 = rotZ(limbDir(side, A.abd + A.eAbd, A.fwd + A.eFwd), -pose.leanSide);
return [shoulder, elbow, add(elbow, mul(d2, FOREARM))];
};
const ar = arm(1, pose.armR), al = arm(-1, pose.armL);
const body = (p) => rotY(p, pose.yaw);
let lowest = Infinity;
for (const p of [...lr, ...ll]) lowest = Math.min(lowest, body(p)[1]);
const dy = FLOOR_Y - lowest + 0.01 + pose.air;
const polys = [];
const place = (p) => { const q = body(p); return [q[0] + pose.tx, q[1] + dy, q[2] + pose.tz]; };
const line = (pts, w = 2.4) => polys.push({ pts: pts.map(place), color: WHITE, w });
line([[0, 0, 0], neck]);
line([hipR, [0, 0, 0], hipL]);
line(ar); line(al);
line(lr.slice(0, 3)); line(ll.slice(0, 3));
line([lr[2], lr[3]], 2.0); line([ll[2], ll[3]], 2.0);
const headPt = (v) => place(add(headC, rotZ(v, -pose.headTilt)));
for (const lat of [-0.5, 0, 0.5]) {
const pts = [], r = HEAD_R * c(lat), y = HEAD_R * s(lat);
for (let k = 0; k <= 18; k++) { const a = TAU * k / 18; pts.push(headPt([r * c(a), y, r * s(a)])); }
polys.push({ pts, color: WHITE, w: 1.2, dim: lat !== 0 });
}
for (let m = 0; m < 4; m++) {
const pts = [], a = PI * m / 4;
for (let k = 0; k <= 18; k++) { const t = TAU * k / 18; pts.push(headPt([HEAD_R * c(t) * c(a), HEAD_R * s(t), HEAD_R * c(t) * s(a)])); }
polys.push({ pts, color: WHITE, w: 1.0, dim: true });
}
for (const A of [ar, al]) {
const h = A[2], pts = [];
for (let k = 0; k <= 10; k++) { const a = TAU * k / 10; pts.push(place(add(h, [0.035 * c(a), 0.035 * s(a), 0]))); }
polys.push({ pts, color: WHITE, w: 1.2 });
}
return polys;
}
// Stage: wooden boards, plus a ripple under the dancer on every beat
const STAGE = 0.8;
function buildFloor(beat, pose) {
const polys = [];
for (let i = 0; i <= 7; i++) {
const z = -STAGE + i * (2 * STAGE / 7);
polys.push({ pts: [[-STAGE, FLOOR_Y, z], [STAGE, FLOOR_Y, z]], color: FLOOR, w: 0.9, dim: true });
// staggered board ends
if (i < 7) {
const x = -STAGE + ((i * 0.53) % 1) * 2 * STAGE, z2 = z + 2 * STAGE / 7;
polys.push({ pts: [[x, FLOOR_Y, z], [x, FLOOR_Y, z2]], color: FLOOR, w: 0.7, dim: true });
}
}
for (const x of [-STAGE, STAGE]) polys.push({ pts: [[x, FLOOR_Y, -STAGE], [x, FLOOR_Y, STAGE]], color: FLOOR, w: 0.9, dim: true });
const ph = beat % 1, r = 0.08 + ph * 0.35, pts = [];
for (let k = 0; k <= 24; k++) { const a = TAU * k / 24; pts.push([pose.tx + r * c(a), FLOOR_Y, pose.tz + r * s(a)]); }
polys.push({ pts, color: WHITE, w: 1.2, alpha: (1 - ph) * 0.8 });
return polys;
}
// ---------- Projection ----------
const CENTER_Y = -0.05;
function project(p, view, jitter) {
let [x, y, z] = p;
y -= CENTER_Y;
if (jitter) { x += (Math.random()-.5)*jitter; y += (Math.random()-.5)*jitter; }
const cy = Math.cos(view.yaw), sy = Math.sin(view.yaw);
const x1 = x * cy + z * sy, z1 = -x * sy + z * cy;
const cx = Math.cos(view.pitch), sx = Math.sin(view.pitch);
const y1 = y * cx - z1 * sx, z2 = y * sx + z1 * cx;
const d = 5, persp = d / (d - z2);
const scale = W * 0.27;
return [W/2 + x1 * scale * persp, H/2 - y1 * scale * persp, z2];
}
function strokeAll(polys, view, color, alpha, ox, oy, jitter) {
for (const poly of polys) {
bctx.beginPath();
let depthSum = 0;
poly.pts.forEach((p, i) => {
const [sx, sy, sz] = project(p, view, jitter);
depthSum += sz;
if (i === 0) bctx.moveTo(sx + ox, sy + oy); else bctx.lineTo(sx + ox, sy + oy);
});
const depth = depthSum / poly.pts.length;
const fade = 0.45 + 0.55 * Math.min(1, Math.max(0, (depth + 1.2) / 2.4));
bctx.globalAlpha = alpha * fade * (poly.dim ? 0.55 : 1) * (poly.alpha ?? 1);
bctx.strokeStyle = color || poly.color;
bctx.lineWidth = poly.w * dpr;
bctx.stroke();
}
bctx.globalAlpha = 1;
}
// ---------- Loop ----------
let glitch = 0, glitchStrength = 0;
let orbit = 0, last = performance.now();
let beatShift = 0;
function frame(now) {
if (W === 0 || H === 0) {
resize();
if (W === 0 || H === 0) { last = now; requestAnimationFrame(frame); return; }
}
const dt = Math.min(50, now - last) / 1000; last = now;
orbit += dt * (reduced ? 0.15 : 0.45);
const t = now / 1000;
let beat = t * (reduced ? BPM / 3 : BPM) / 60;
if (!reduced && glitch <= 0 && Math.random() < 0.025) {
glitch = 4 + Math.floor(Math.random() * 10);
glitchStrength = 0.4 + Math.random() * 0.6;
beatShift = Math.random() < 0.5 ? -Math.random() * 0.4 : 0; // the dancer skips back, time keeps flowing
}
const g = glitch > 0;
if (g) glitch--; else beatShift = 0;
beat += beatShift;
const view = { yaw: orbit, pitch: 0.22 + Math.sin(t * 0.7) * 0.04 };
const pose = poseAt(beat);
const polys = buildFloor(beat, pose).concat(buildFigure(pose));
bctx.clearRect(0, 0, W, H);
bctx.lineJoin = 'round'; bctx.lineCap = 'round';
bctx.globalCompositeOperation = 'lighter';
if (g) {
const off = (4 + Math.random() * 8) * dpr * glitchStrength;
strokeAll(polys, view, GHOST_A, 0.7, -off, 0, 0.03 * glitchStrength);
strokeAll(polys, view, GHOST_B, 0.6, off, (Math.random()-.5)*2*dpr, 0.03 * glitchStrength);
}
strokeAll(polys, view, null, g ? 0.85 : 1, 0, 0, g ? 0.02 : (reduced ? 0 : 0.004));
bctx.globalCompositeOperation = 'source-over';
ctx.clearRect(0, 0, W, H);
if (g) {
let y = 0;
while (y < H) {
const h = Math.min(H - y, Math.max(2, Math.floor((4 + Math.random() * 30) * dpr)));
const shift = Math.random() < 0.35 ? (Math.random() - .5) * 40 * dpr * glitchStrength : 0;
ctx.drawImage(buf, 0, y, W, h, shift, y, W, h);
y += h;
}
const blocks = Math.floor(Math.random() * 4);
for (let i = 0; i < blocks; i++) {
ctx.fillStyle = [WHITE, GHOST_A, GHOST_B][i % 3];
ctx.globalAlpha = 0.18 + Math.random() * 0.3;
ctx.fillRect(Math.random() * W, Math.random() * H, (10 + Math.random() * 60) * dpr, (1 + Math.random() * 3) * dpr);
}
ctx.globalAlpha = 1;
} else {
ctx.drawImage(buf, 0, 0);
}
requestAnimationFrame(frame);
}
requestAnimationFrame(frame);
})();
</script>
</body>
</html>