text: var side = 20;
  var x = 0;
  var y = 0;
  
  function setup() {
  	createCanvas(300, 300);
  }
  
  function draw() {
  	background(255);
  	for (var y = 0; y < height; y += side) {
  		for(x = 0; x < width; x += side){
  			noStroke();
  			if ((x + y) % (side * 2) == 0) {
  				fill(0);
  			} else {
  				fill(255)
  			}
  			
  			rect(x, y, side, side);
  		}
  	}
  
  }