30:T930,class Crack { constructor() { this.findStart(); this.sp = new SandPainter(); } static makeCrack() { if (cracks.length < maxnum) { cracks.push(new Crack()); } } findStart() { let px = 0, py = 0; let found = false; let timeout = 0; while (!found || (timeout++ > 1000)) { px = Math.floor(Math.random() * dimx); py = Math.floor(Math.random() * dimy); if (cgrid[py * dimx + px] < 10000) { found = true; } } if (found) { let a = cgrid[py * dimx + px]; if (Math.random() < 0.5) { a -= 90 + Math.floor(Math.random() * 4.1 - 2); } else { a += 90 + Math.floor(Math.random() * 4.1 - 2); } this.startCrack(px, py, a); } } startCrack(X, Y, T) { this.x = X; this.y = Y; this.t = T; this.x += 0.61 * Math.cos(this.t * Math.PI / 180); this.y += 0.61 * Math.sin(this.t * Math.PI / 180); } move() { this.x += 0.42 * Math.cos(this.t * Math.PI / 180); this.y += 0.42 * Math.sin(this.t * Math.PI / 180); let z = 0.33; let cx = Math.floor(this.x + Math.random() * 2 * z - z); let cy = Math.floor(this.y + Math.random() * 2 * z - z); this.regionColor(); context.globalAlpha = 0.85; context.fillStyle = "#000"; context.fillRect( this.x + Math.random() * 2 * z - z, this.y + Math.random() * 2 * z - z, 1, 1 ); if ((cx >= 0) && (cx < dimx) && (cy >= 0) && (cy < dimy)) { if ((cgrid[cy * dimx + cx] > 10000) || (Math.abs(cgrid[cy * dimx + cx] - this.t) < 5)) { cgrid[cy * dimx + cx] = Math.floor(this.t); } else if (Math.abs(cgrid[cy * dimx + cx] - this.t) > 2) { this.findStart(); Crack.makeCrack(); } } else { this.findStart(); Crack.makeCrack(); } } regionColor() { let rx = this.x; let ry = this.y; let openspace = true; while (openspace) { rx += 0.81 * Math.sin(this.t * Math.PI / 180); ry -= 0.81 * Math.cos(this.t * Math.PI / 180); let cx = Math.floor(rx); let cy = Math.floor(ry); if ((cx >= 0) && (cx < dimx) && (cy >= 0) && (cy < dimy)) { if (cgrid[cy * dimx + cx] <= 10000) { openspace = false; } } else { openspace = false; } } this.sp.render(rx, ry, this.x, this.y); } }31:[] 2e:{"title":"Substrate","cells":[{"id":0,"value":"md`# Substrate\n\nA port of Jared Tarbell’s [*Substrate* (2003)](http://www.complexification.net/gallery/machines/substrate/).`","pinned":false,"hidden":false,"mode":"ojs"},{"id":104,"value":"viewof restart = html`