let mDiam = 40;

​

let x0 = 80;

let y0 = 135;

​

function setup() {

  createCanvas(windowWidth, windowHeight);

}

​

function draw() {

  background(220, 10, 120);

  fill(255);

  stroke(0);

​

  ellipse(x0, y0, oDiam);

​

  let d = sqrt((mouseX - x0) ** 2 + (mouseY - y0) ** 2);

​

  if (d < oDiam / 2 + mDiam / 2) {

    fill(255, 0, 0);

  }

​

  ellipse(mouseX, mouseY, mDiam);

}

​