Shiver　blue

let NUM = 20;

let vecLocation = [];

let vecVelocity = [];

​

function setup() {

  createCanvas(windowWidth, windowHeight);

  background(100);

  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(0,127,255);

  for (let i = 0; i<NUM;i++){

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

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

    if(vecLocation[i].x < random(0,width/3) || vecLocation[i].x > random(width*2/3,width)){

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

    }

    if(vecLocation[i].y < random(0,height/3) || vecLocation[i].y >random(height*2/3,height)){

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

    }

  }

}