createCanvas(400, 400);

}

​

function draw() {

  background(220);

  let half = 200;

  if (mouseX < half && mouseY < half) {

    fill(100,200,0);

    square(0,0,half);

  }

  if (mouseX > half && mouseY < half) {

    fill(200,100,0);

    square(half,0,half);

  }

  if (mouseX < half && mouseY > half) {

    fill(0,100,200);

    square(0,half,half);

  }

  if (mouseX > half && mouseY > half) {

    fill(200,0,100);

    square(half, half,half);

  }

}