var stepY;

​

function setup() {

  createCanvas(800,800);

//ss  noStroke();

  colorMode(HSB, width, height, 100);

}

​

function draw() {

  stepX = mouseX+10;

  stepY = mouseY+10;

  for (var gridY = 0; gridY < height; gridY += stepY) {

    for (var gridX = 0; gridX < width; gridX += stepX) {

      fill(gridX, height - gridY, 100);

      rect(gridX, gridY, stepX, stepY);

    }

  }

}