var position2, velocity2, size2;

​

function setup() {

  createCanvas(400, 400);

  position1 = createVector(100,100);

  velocity1 = createVector(2,1);

  size1 = createVector(10, 10);

  position2 = createVector(200,200);

  velocity2 = createVector(-4,2);

  size2 = createVector(10, 10);

}

​

function draw() {

  background(240);

  noStroke();

  fill(200,0,200);

  ellipse(position1.x, position1.y, size1.x, size1.y);

  position1.add(velocity1);

  if (position1.x > 400 || position1.x < 0) {

    velocity1.x *= -1;

  }

  if (position1.y > 400 || position1.y < 0) {

    velocity1.y *= -1;

  }

  noStroke();

  fill(255,100,0);

  ellipse(position2.x, position2.y, size2.x, size2.y);

  position2.add(velocity2);

  if (position2.x > 400 || position2.x < 0) {

    velocity2.x *= -1;

  }

  if (position2.y > 400 || position2.y < 0) {

    velocity2.y *= -1;

  }

  if (position1.x == position2.x) {

    size1.x += 10;

    size2.y += 10;

  }

}