createCanvas(400, 400);

}

​

function draw() {

  background(220);

  noStroke()

  fill(255, 0, 0)

  if (mouseX > width*2/3 && mouseX < width){

    rect(width*2/3, 0, width/3, height);

  }

  else if (mouseX > width/3 && mouseX < width*2/3){

    rect(width/3, 0, width/3, height);

  }

  else if (mouseX > 1 && mouseX < width/3)  { 

    rect(0, 0, width/3, height);

  }

}