createCanvas(400, 400);

}

​

function draw() {

  background(225);

​

  //the size of the squares

  var rsize = 5

  var x = 0;

  while (x < width) {

    var y = 0;

    //for every x there is y

      while (y < height) {

      //color

var red = map(x,0,400,255,0);

  var red2 = map(y,0,400,0,255);

  var green = map(y,0,400,0,255);

  var blue = map(x,0,400,0,255);

  var blue2 = map(y,0,400,0,255);

        fill(red2-red,green,blue-blue2)

        rect(x, y, rsize,rsize);

        y = y + 5;

      }

    x = x + 5;

  }

}