​

function setup() {

  createCanvas(400, 400);

  gridSlider = createSlider(10, 40, 20);

}

​

function draw() {

  background(255,255,100);

  stroke(0);

  DrawGrid(400, gridSlider.value());

}

​

function DrawGrid(MAX,SPACING) {  

  // parameters MAX and SPACING allow us to pass values into the function

  for (var g = 0; g < MAX; g = g + SPACING) {

    strokeWeight(1);

    line(g, 0, g, MAX);

    line(0, g, MAX, g);

  }

  // setting up the mid-point lines

  strokeWeight(3);

  line(0, MAX/2, MAX, MAX/2);

  line(MAX/2, 0, MAX/2, MAX);

}

​