// create a CanvasOverlayer on Mapbox map instance..
var canvasLayer = new Alex.CanvasOverlayer({
    map: map,
    shadow: false,
    keepTrack: true,
    blurWidth: 4
});

// create a Drone inherites Sprite Class
var drone = new Alex.Drone({
    direction: 45,
    icon: "https://alex2wong.github.io/mapbox-plugins/assets/tri2.png"
});

// add keyboard control to Sprite.
Alex.Controllers.gameControl(drone);
function update(){
    drone.updateStatus();
    // render drone on canvasLayer.
    canvasLayer.redraw([drone]);
    requestAnimationFrame(update);
}
update();