let stars = [];

​

function setup() {

  createCanvas(600, 600);

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

    stars.push(new Star(random(width), random(height)));

  }

  stroke(255);

}

​

function draw() {

  background(0, 50);

  const acc = map(mouseX, 0, width, 0.005, 0.2);

  stars = stars.filter(star => {

    star.draw();

    star.update(acc);

    return star.isActive();

  });

  while(stars.length < numStars) {

    stars.push(new Star(random(width), random(height)));

  }

}

​

class Star {

  constructor(x, y) {

    this.pos = createVector(x, y);

    this.prevPos = createVector(x, y);

    this.vel = createVector(0, 0);

    this.ang = atan2(y - (height/2), x - (width/2));

  }

  isActive() {

    return onScreen(this.prevPos.x, this.prevPos.y);

  }

  update(acc) {

    this.vel.x += cos(this.ang) * acc;

    this.vel.y += sin(this.ang) * acc;

    this.prevPos.x = this.pos.x;

    this.prevPos.y = this.pos.y;

    this.pos.x += this.vel.x;

    this.pos.y += this.vel.y;

  }

  draw() {

    const alpha = map(this.vel.mag(), 0, 3, 0, 255);

    stroke(255, alpha);

    line(this.prevPos.x, this.prevPos.y, this.pos.x, this.pos.y);

  }

}

​

function onScreen(x, y) {

  return x >= 0 && x <= width && y >= 0 && y <= height;  

}