let h;

function setup() {

  createCanvas(400, 400);

  colorMode(HSB, 360, 100, 100);

}

​

function draw() {

h = mouseX

    fill(h, 100, 100)

rect(0,0, width/2, height)

      fill(h/2, 100, 100)

  if (h == 360){

  }

  else {

    h = mouseX

  }

  rect(width/2,0, width/2, height)

​

}

​