createCanvas(600, 400);

}

​

function draw() {

  background(220);

  if(mouseX < 200) {

  fill('red');

  rect(0, 0, 200, height);

  fill('white');

  rect(200, 0, 200, height);

  fill('white');

  rect(400, 0, 200, height);

  }

​

  else if(200 <= mouseX && mouseX < 400) {

  fill('white');

  rect(0, 0, 200, height);

  fill('red');

  rect(200, 0, 200, height);

  fill('white');

  rect(400, 0, 200, height);

  }

  else if(400 <= mouseX) {

  fill('white');

  rect(0, 0, 200, height);

  fill('white');

  rect(200, 0, 200, height);

  fill('red');

  rect(400, 0, 200, height);

  }

}