createCanvas(400, 400);

 // colorMode(HSB, 400);

  for (let a = 0; a < 300; a++) {

    for (let b = 0; b < 100; b++) {

    stroke(a, b, 400);

    point(a, b);

    }

  }

}

​

function draw() {

//  background(mouseY/2, mouseX, mouseY);

  background(mouseY/2, 150, 400);

  translate(width / 2, height / 2);

​

  var circleResolution = map(mouseY, 0, height, 2, 80);

  var radius = mouseX - width / 2 + 0.5;

  var angle = TWO_PI / circleResolution;

  strokeWeight(mouseY / 20);

  beginShape();

  for(var i = 0; i <= circleResolution; i++) {

    var x = cos(angle * i) * radius;

    var y = sin(angle * i) * radius;

    line(0, 0, x, y);

  }

  endShape(CLOSE);

}