let h;

let c; 

​

function setup() {

  createCanvas(windowWidth, windowHeight);

  colorMode(HSB, 360, 100, 100);

}

​

function draw() {

h = map(mouseX, 0, windowWidth/2, 0, 360)

    fill(h%360, 100, 100)

rect(0,0, windowWidth/2, windowHeight)

  c = h+180

      fill(c%360, 100, 100)

​

  rect(windowWidth/2,0, windowWidth/2, windowHeight)

​

}

​