[]

];

let index = 0;

​

function setup() {

  createCanvas(400, 400);

}

​

function mouseReleased() {

  histories.push([]);

  index++;

}

​

function draw() {

  background(220);

  if (mouseIsPressed) {

    histories[index].push([mouseX, mouseY]);

  }

  for (let history of histories) {

    noFill();

    beginShape();

    for (let p of history) {

      vertex(...p);

    }

    endShape();

  }

}