w = 1000;

h = 1000;

​

​

function setup() {

  createCanvas(w, h);

}

​

function draw() {

  background(220);

  stroke("red");

  strokeWeight(10);

  verticalLine(mouseX);

  horizontalLine(50);

  let divider = 50;

  strokeWeight(2);

  draw_grid(divider);

}

​

​

function verticalLine(x)

{

  line(x, 0, x, height);

}

​

​

function horizontalLine(y)

{

  line(0, y, width, y);

}

​

​

function draw_grid(divider)

{

  stroke("blue");

  for (let i = 0; i < width; i += divider)

  {

    for (let j = 0; j < height; j += divider)

    {

      verticalLine(i);

      horizontalLine(j);

    }

  }

}