let vecVelocity = [];

const NUM = 50;

​

function setup() {

  createCanvas(windowWidth, windowHeight);

  frameRate(60);

  for(let i = 0; i < NUM; i++){

    vecLocation[i] = createVector(width/2, height/2);

    vecVelocity[i] = createVector(random(-10, 10), random(-10, 10));

  }

}

​

function draw() {

  background(0);

  noStroke();

  fill(255);

  for(let i = 0; i < NUM; i++){

    ellipse(vecLocation[i].x, vecLocation[i].y, 20, 20);

    vecLocation[i].add(vecVelocity[i]);

    if(vecLocation[i].x > width || vecLocation[i].x < 0) { //OR

      vecVelocity[i].x = vecVelocity[i].x * -1;

    }

    if(vecLocation[i].y > height || vecLocation[i].y < 0) { //OR

      vecVelocity[i].y = vecVelocity[i].y * -1;

    }

  }

}

​

​

​

​

​