Processing Evolved

    function setup() {
        let canvas = createCanvas(600, 600, WEBGL);
        canvas.parent('animation-holder');
    resizeAnimation();
    resizeAnimation();
    resizeAnimation();
    }

    let particles = [];
    let boxAngle = 0;
    let boxColor = [0, 128, 0];

    function draw() {
        background(150);
        push();
        rotateX(boxAngle);
        rotateY(boxAngle * 0.5);
        rotateZ(boxAngle * 0.25);
        fill(boxColor[0], boxColor[1], boxColor[2]);
        square(-50, -50, 100);
        pop();

        boxAngle += 0.01;
        boxColor[0] = (boxColor[0] + 1) % 256;
        boxColor[1] = (boxColor[1] + 2) % 256;
        boxColor[2] = (boxColor[2] + 3) % 256;

        for (let i = 0; i < 10; i++) {
            particles.push(new Particle());
        }

        for (let p of particles) {
            p.update();
            p.show();
        }
    }

    class Particle {
        constructor() {
            this.pos = createVector(random(-50, 50), random(-50, 50));
            this.vel = p5.Vector.random2D();
            this.vel.mult(random(2, 5));
            this.alpha = 255;
        }

        update() {
            this.pos.add(this.vel);
            this.alpha -= 5;
        }

        show() {
            noStroke();
            fill(128, 0, 128, this.alpha);
            ellipse(this.pos.x, this.pos.y, 10);
        }
    }