createCanvas(400, 400);

}

​

function draw() {

  background(0);

  noFill()

  stroke(255)

  strokeWeight(4)

  circle(width/2,height/2,100)

​

  if (mouseX>width/2) {

    fill(255,0,0)

    circle(width/2,height/2,100)

  }

}