particles

class Particle {
      x = Math.random() * canvas.width;
      y = Math.random() * canvas.height;
      vx = Math.random();
      vy = Math.random();
      id;
      life = 0;
      maxLife = 40;

      constructor() {
        particleIndex++;
        particles[particleIndex] = this;
        this.id = particleIndex;
      }

      draw() {
        this.x += this.vx;
        this.y += this.vy;
        this.life++;

        if (this.life === this.maxLife) delete particles[this.id];

        ctx.fillStyle = 'white';
        ctx.fillRect(this.x, this.y, 10, 10);
      }
    }



    loop();

    function loop() {
      requestAnimationFrame(() => {
        ctx.fillStyle = 'black';
        ctx.fillRect(0, 0, canvas.width, canvas.height);

        const particlesLen = particles.filter((a) => a !== undefined).length;
        for (let i = 0; i < particleNum; i++) {
          if (particlesLen < 5) {
            new Particle();
          }
        }

        particles.forEach(p => p.draw());
        loop();
      })
    }