const BALL_SIZE = 30;

const BALL_AGE = 1000;

​

const balls = [];

​

class Ball {

  constructor(x, y, dir, col) {

    this.pos = createVector(x, y);

    this.vel = createVector(BALL_SPEED, BALL_SPEED);

    this.vel.rotate(radians(dir));

    this.col = col;

    this.srk = [0, 0, 0, 150];

    this.age = BALL_AGE;

  }

  draw() {

    if (this.age <= BALL_AGE * 0.1) {

      this.col = [

        red(this.col),

        green(this.col),

        blue(this.col),

        alpha(this.col) * 0.8

      ];

      this.srk = [

        red(this.srk),

        green(this.srk),

        blue(this.srk),

        alpha(this.srk) * 0.8

      ]

    }

    push();

    translate(this.pos.x, this.pos.y);

    fill(this.col);

    stroke(this.srk);

    circle(0, 0, BALL_SIZE);

    pop();

  }

  move() {

    if (this.pos.x < 0) { // left border 

      let sn = createVector(BALL_SPEED, 0);

      this.vel.reflect(sn);

    } else if (this.pos.x > windowWidth) { // right border

      let sn = createVector(-BALL_SPEED, 0);

      this.vel.reflect(sn);

    } else if (this.pos.y < 0) { // top border

      let sn = createVector(0, BALL_SPEED);

      this.vel.reflect(sn);

    } else if (this.pos.y > windowHeight) { // bottom border

      let sn = createVector(0, -BALL_SPEED);

      this.vel.reflect(sn);

    }

    this.pos.add(this.vel);

  }

  run() {

    this.age--;

    if (this.age > 0) {

      this.draw();

      this.move();

    }

  }

}

​

​

function setup() {

  createCanvas(windowWidth, windowHeight);

  let col = [

    random(0, 255),

    random(0, 255),

    random(0, 255),

    150

  ];

  let ball = new Ball(

    random(10, windowWidth - 10),

    random(10, windowHeight - 10),

    random(0, 360),

    col

  );

  balls.push(ball);

}

​

function draw() {

  background("#B7EDFF");

  balls.forEach(b => b.run());

}

​

function mouseDragged() {

  let col = [

    random(0, 255), 

    random(0, 255), 

    random(0, 255),

    150

  ];

  let b = new Ball(mouseX, mouseY, random(0, 360), col);

  balls.push(b);

}