constructor(){

    this.x = random(width-100);

    this.y = random(height-100);

  }

  draw(_num){

    rectMode(CENTER);

    rect(this.x, this.y, 100,100);

    textAlign(CENTER, CENTER);

    text(str(_num), this.x, this.y);

  }

}

​

var boxes = [];

function setup() {

  createCanvas(windowWidth, windowHeight);

  for( let i = 0; i < 10; i++ ){

    boxes.push(new Box());

  }

}

​

function draw() {

  background(220);

  for( let i = 0; i < boxes.length; i++ ){

    boxes[i].draw(i);

  }

}

​

function keyPressed()

{

  if( key == 'p' ){ // push

    boxes.push(new Box());

  }

  else if( key == 's' ){  // splice

    boxes.splice(random(boxes.length), 1);

  }

}