let anchors

let idx

let leng = 10

let size = 200

let px = 0

let py = 0

function seed() {

  idx = 0

  anchors = (Date.now() + '').split``

    .reverse()

    .map(v => parseFloat(v) / 10)

    .splice(0, leng)

}

let last = 0

let zoom = 1

function rand() {

  if (idx > size * size) seed()

  px += zoom

  py += ~~(px / size)

  if (px >= size) px = 0

  if (py >= size) py = 0

  const point = {

    x: anchors[idx % leng],

    y: anchors[(idx + 1) % leng]

  }

  idx++

  let dists = []

  for (let i = 0; i < anchors.length; i += 2) {

    let dx = px - anchors[i] * size

    let dy = py - anchors[i + 1] * size

    dists.push(Math.sqrt(dx * dx + dy * dy))

  }

  dists.sort()

  last += (dists[0] / size - last) / 4

  return last

}

seed()

let d = document

let b = d.body

with (b.appendChild(

  Object.assign(d.createElement`canvas`, { width: 400, height: 400 })

).getContext`2d`) {

  fillStyle = 'black'

  fillRect(0, 0, 400, 400)

  for (let i = 0; i < 200; i++) {

    for (let j = 0; j < 200; j++) {

      const c = rand() * 255

      fillStyle = `rgb(${c}, ${c}, ${c})`

      fillRect(j * 2, i * 2, 1, 2)

    }

  }

}