Фейерверк на канвас

const rndColor = () => {
    const base  = Math.random() * 360 | 0;
    const color = (275 * (base / 200 | 0)) + base % 200;
    return fac => `hsl(${color}, ${(fac || 1) * 100}%, ${(fac || 1) * 60}%)`;
};

class Battery
{
    constructor(fireworks) {
        this.fireworks = fireworks;
        this.salve = [];
        this.x     = Math.random();
        this.t     = 0;
        this.tmod  = 20 + Math.random() * 20 | 0;
        this.tmax  = 500 + Math.random() * 1000;

        this._shot = salve => {
            // console.log(this.x * this.fireworks.width, salve.y);
            if (salve.y < salve.ym) {
                salve.cb = this._prepareExplosion;
            }

            salve.x += salve.mx;
            salve.y -= 0.01;

            const r = Math.atan2(-0.01, salve.mx);

            this.fireworks.engine.strokeStyle = salve.c(.7);
            this.fireworks.engine.beginPath();

            this.fireworks.engine.moveTo(
                (this.x + salve.x) * this.fireworks.width + Math.cos(r) * 4,
                salve.y * this.fireworks.height + Math.sin(r) * 4
            );

            this.fireworks.engine.lineTo(
                (this.x + salve.x) * this.fireworks.width + Math.cos(r + Math.PI) * 4,
                salve.y * this.fireworks.height + Math.sin(r + Math.PI) * 4
            );

            this.fireworks.engine.lineWidth = 3;
            this.fireworks.engine.stroke();

            // this.fireworks.engine.fillRect((this.x + salve.x) * this.fireworks.width, salve.y * this.fireworks.height, 10, 10);
        };

        this._prepareExplosion = salve => {
            salve.explosion = [];

            for (let i = 0, max = 32; i < max; i++) {
                salve.explosion.push({
                    r : 2 * i / Math.PI,
                    s : 0.5 + Math.random() * 0.5,
                    d : 0,
                    y : 0
                });
            }

            salve.cb = this._explode;
        };

        this._explode = salve => {

            this.fireworks.engine.fillStyle = salve.c();

            salve.explosion.forEach(explo => {

                explo.d += explo.s;
                explo.s *= 0.99;
                explo.y += 0.5;

                const alpha = explo.s * 2.5;
                this.fireworks.engine.globalAlpha = alpha;

                if (alpha < 0.05) {
                    salve.cb = null;
                }

                this.fireworks.engine.fillRect(
                    Math.cos(explo.r) * explo.d + (this.x + salve.x) * this.fireworks.width,
                    Math.sin(explo.r) * explo.d + explo.y + salve.y * this.fireworks.height,
                    3,
                    3
                );
            });

            this.fireworks.engine.globalAlpha = 1;
        }
    }

    pushSalve() {
        this.salve.push({
            x: 0,
            mx: -0.02 * Math.random() * 0.04,
            y: 1,
            ym: 0.05 + Math.random() * 0.5,
            c: rndColor(),
            cb: this._shot
        });
    };

    render() {

        this.t++;

        if (this.t < this.tmax && (this.t % this.tmod) === 0) {
            this.pushSalve();
        }

        let rendered = false;

        this.salve.forEach(salve => {

            if (salve.cb) {
                rendered = true;
                salve.cb(salve);
            }

        });

        if (this.t > this.tmax) {
            return rendered;
        }

        return true;
    }
}

class Fireworks
{
    constructor() {
        this.canvas = window.document.querySelector('canvas');
        this.engine = this.canvas.getContext('2d');
        this.stacks = new Map();

        this.resize();
    }

    resize() {
        this.width  = window.innerWidth;
        this.height = window.innerHeight;

        this.canvas.setAttribute('width', this.width);
        this.canvas.setAttribute('height', this.height);
    }

    clear() {
        this.engine.clearRect(0, 0, this.width, this.height);
        this.engine.fillStyle = '#222';
        this.engine.fillRect(0, 0, this.width, this.height);
    }

    addBattery() {
      const bat = new Battery(this);
      this.stacks.set(Date.now(), bat);  
    }
  
    render() {

        if (Math.random() < 0.05) {
          this.addBattery();
        }
      
        this.clear();

        this.stacks.forEach((scene, key) => {

            const rendered = scene.render();

            if (!rendered) {
                this.stacks.delete(key);
            }
        });

        requestAnimationFrame(this.render.bind(this));
    }

    run() {
        for(let i = 0; i < 5; i++) {
          this.addBattery();
        }
        window.addEventListener('resize', this.resize.bind(this));
        this.render();
    }
}

a = new Fireworks();
a.run();