step1.html

<html>
    <head>
        <meta charset="utf-8">
        <meta name="viewport" content="width=device-width,initial-scale=1,maximum-scale=1,user-scalable=no">
        <title>Multiblaster</title>
        <style>
            html, body {
                margin: 0;
                height: 100%;
                background: #999;
            }
            #canvas {
                background: #000;
                object-fit: contain;
                max-width: 100%;
                max-height: 100%;
            }
        </style>
        <script src="https://cdn.jsdelivr.net/npm/@multisynq/client@1.0.2/bundled/multisynq-client.min.js"></script>
    </head>
    <body>
        <canvas id="canvas" width="1000" height="1000"></canvas>
        <script>

class Game extends Multisynq.Model {
    init() {
        this.asteroids = new Set();
        this.asteroids.add(Asteroid.create());
        this.asteroids.add(Asteroid.create());
        this.asteroids.add(Asteroid.create());
   }
}
Game.register("Game");

class Asteroid extends Multisynq.Model {
    init() {
        this.size = 40;
        this.x = Math.random() * 1000;
        this.y = Math.random() * 1000;
        this.dx = Math.random() * 6 - 3;
        this.dy = Math.random() * 6 - 3;
        this.a = Math.random() * Math.PI * 2;
        this.da = (0.02 + Math.random() * 0.03) * (Math.random() < 0.5 ? 1 : -1);
        this.move();
    }

    move() {
        this.x = (this.x + this.dx + 1000) % 1000;
        this.y = (this.y + this.dy + 1000) % 1000;
        this.a = (this.a + this.da + Math.PI) % Math.PI;
        this.future(50).move(); // keep moving every 50 ms
    }
}
Asteroid.register("Asteroid");

////////////////////////// VIEW //////////////////////////

class Display extends Multisynq.View {
    constructor(model) {
        super(model);
        this.model = model;
        this.context = canvas.getContext("2d");
    }

    // update is called once per render frame
    update() {
        this.context.clearRect(0, 0, 1000, 1000);
        this.context.lineWidth = 3;
        this.context.strokeStyle = "white";
        for (const asteroid of this.model.asteroids) {
            const { x, y, a, size } = asteroid;
            this.context.save();
            this.context.translate(x, y);
            this.context.rotate(a);
            this.context.beginPath();
            this.context.moveTo(+size,  0);
            this.context.lineTo( 0, +size);
            this.context.lineTo(-size,  0);
            this.context.lineTo( 0, -size);
            this.context.closePath();
            this.context.stroke();
            this.context.restore();
        }
    }
}


Multisynq.Session.join({
    apiKey: '234567_Paste_Your_Own_API_Key_Here_7654321', // get your own from multisynq.io/coder
    appId: 'io.multisynq.multiblaster-tutorial',
    model: Game,
    view: Display,
});
        </script>
    </body>
</html>