const pointsV = 20

​

function setup() {

  createCanvas(400, 400);

}

​

function draw() {

  background(0);

  const h = width / pointsH

  const v = height / pointsV

  translate(10, 10)

  for (let x = 0; x < width; x += h) {

    for(let y = 0; y < height; y += v) {

      stroke(100)

      rect(x-2.5, y-2.5, 5, 5)

      stroke(255, 255, 255, 100)

      if ((mouseX >= width || mouseX <= 0) || (mouseY <= 0 || mouseY >= height)) {

        line(x, y, width/2, height/2)

      } else {

        line(x, y, mouseX, mouseY)

      }

    }

  }

}