start method
Implementation
void start(Scene scene) {
canvas = querySelector("#game") as CanvasElement;
gl = canvas.getContext("webgl") as WebGL.RenderingContext;
Util.initGl();
Texture.loadAll();
input = Input();
this.scene = scene;
scene.init();
screen = Screen(gl, scene.camera);
window.requestAnimationFrame(animate);
}