function setup() {

  createCanvas(500, 500);

  background(random(200,255),random(200,255),random(200,255));

}

​

function draw() {

  noStroke();

  fill(mouseX, mouseY, 0,50);

  square(100, 100, 100);

  fill(mouseX - 150, mouseY, 0,50);

  square(300, 100, 100);

  fill(mouseX - 150, mouseY - 150, 0,50);

  square(300, 300, 100);

  fill(mouseX, mouseY - 150, 0,50);

  square(100, 300, 100);

}

​

function mousePressed() {

  background(random(200,255),random(200,255),random(200,255));

}

​