createCanvas(400, 400);

  pixelDensity(1);

}

​

function draw() {

  background(51);

  loadPixels();

  for (let y=0; y<height; y++){

    for (let x=0; x<width/2; x++){

      let index = (x+y*width)*4;

      pixels[index + 0] = mouseX;

      pixels[index + 1] = random(255);

      pixels[index + 2] = y;

      pixels[index + 3] = random(255);

    }

    for (let x=0; x<(width/2+width/2); x++){

      let index = (x+y*width)*4;

      pixels[index + 0] = mouseX;

      pixels[index + 1] = (mouseX+mouseY)/2;

      pixels[index + 2] = mouseY;

      pixels[index + 3] = 100;

    }

  }

  updatePixels();

}