​

let size = 30; 

​

function setup() {

  createCanvas(400, 400);

}

​

​

function draw() {

  background(237, 34, 93);

  fill(0);

  ellipse(200, 200, size, size);

}

​

function mouseWheel(event) {

  print(event.delta);

  //move the square according to the vertical scroll amount

  size = size + event.delta/20;

  //uncomment to block page scrolling

  //return false;

}