let y_pos = 0;

let time = 0;

​

function setup() {

  createCanvas(1260, 720);

  frameRate(60);

}

​

function draw() {

  background("white");

  time = time + 1;

​

  if (time % 10 === 0) {

    square(pmouseX - 12.5, pmouseY - 12.5, 25);

    fill("black");

    noStroke();

  } else {

    square(pmouseX - 12.5, pmouseY - 12.5, 25);

    fill("white");

    noStroke();

  }

}

​