CloudInvaders/js/cloud.js

const VELOCITY = [0.002, 0.0001];
const SHOOT_PROBABILITY = 0.0007;

class Cloud extends Entity {
    static shootProbability = SHOOT_PROBABILITY;

    constructor(...args) {
        super(...args);

        this.particles = new Set();

        for (let i = 0; i < 3; i++) {
            const cloudParticle = {
                w: randRange(0.3, 0.8),
                h: randRange(0.3, 0.8),
                x: randRange(0.2, 0.8),
                y: randRange(0.2, 0.8),
                r: randRange(-Math.PI, Math.PI),
                n: randRange(-10000, 10000),
            }

            this.particles.add(cloudParticle);
        }
    }

    draw() {
        const { x, y, w, h } = this.getScreenCoords();

        for (let particle of this.particles) {
            const px = x + particle.x * w;
            const py = y + particle.y * h;
            const pw = particle.w * w;
            const ph = particle.h * w;
            const now = Date.now() / 1000;

            const a = mapNumber(
                noise.simplex3(particle.n, now / 2, 0),
                -1, 1,
                0, 0.7,
            );
            const r = mapNumber(
                noise.simplex3(particle.n, now / 10, 1),
                -1, 1,
                0, Math.PI,
            );
            const z = mapNumber(
                noise.simplex3(particle.n, now / 2, 2),
                -1, 1,
                0.5, 1.5,
            );
            CTX.fillStyle = `rgba(255, 255, 255, ${a})`;
            CTX.beginPath();
            CTX.ellipse(px, py, pw / 2 * z, ph / 2 * z, particle.r + r, 0, 2 * Math.PI);
            CTX.fill();
        }
    }

    static reset() {
        this.shootProbability = SHOOT_PROBABILITY;
    }

    update(direction) {
        if (this.alive) {
            this.x += VELOCITY[0] * direction;
            this.y += VELOCITY[1];

            if (Math.random() < Cloud.shootProbability) {
                const raindrop = new RainDrop(this.x, this.y + 0.009);
                bullets.add(raindrop);
            }
        }
    }

    destroy() {
        super.destroy();
        Cloud.shootProbability += 0.0001;
    }
}