let centerY;

let radius;

let brushRadius = 8;

let dotRadiusMin = 0.1;

let dotRadiusMax = 8;

let powerBase = 1.8;

let allDots;

​

function setup()

{

  createCanvas(400, 400);

  Begin();

}

​

function keyPressed()

{

  if (keyCode === 32)

    Begin();

}

​

function draw()

{

  if (mouseX >= width || mouseY >= height)

    return;

  for (let x = mouseX - brushRadius; x <= mouseX + brushRadius; ++x)

  {

    for (let y = mouseY - brushRadius; y <= mouseY + brushRadius; ++y)

    {

      let dx = x - mouseX;

      let dy = y - mouseY;

      let distSq = dx * dx + dy * dy;

      if (distSq > brushRadius * brushRadius)

        continue;

      AttemptDrawPoint(x, y);

    }

  }

}

​

function Begin()

{

  blendMode(BLEND);

  background(40);

  blendMode(ADD);

  allDots = new Set();

  centerX = 400 * Math.random();

  centerY = 400 * Math.random();

  radius = (200 - 10) * Math.random() + 10;

}

​

function AttemptDrawPoint(x, y)

{

  let key = y * width + x;

  if (allDots.has(key))

    return;

  allDots.add(key);

  DrawPoint(x, y);

}

​

function DrawPoint(x, y)

{

  let distance = dist(centerX, centerY, x, y);

  let delta = abs(distance - radius);

  let alpha = pow(powerBase, -delta);

  stroke(alpha * 250, alpha * 180, alpha * 50);

  strokeWeight((dotRadiusMax - dotRadiusMin) * pow(Math.random(), 3) + dotRadiusMin);

  point(x, y);

}

​