async function* show(z, visibility) {
await visibility();
const context = DOM.context2d(width, height);
yield context.canvas;
context.fillStyle = "rgba(20, 150, 240, 0.6)";
let i = 0;
const radius = Math.sqrt((width * height) / N / 2.5);
for (const p of z) {
context.beginPath();
context.arc(p[0], p[1], 0.65 * radius, 0, 2 * Math.PI);
context.fill();
if (i++ % 40 === 0) yield context.canvas;
}
}