Phaser virtual joystick

stick.ts

/// <reference path="../lib/phaser.d.ts"/>
/// <reference path="../lib/socket.io.d.ts"/>
/// <reference path="ship.ts"/>

module AstRoidGame {
    export class ControlStick extends Phaser.Group {
        controlField: Phaser.Sprite;
        stickCenterPos: Phaser.Point;
        stick: Phaser.Sprite;
        game: Phaser.Game;
        isUp: boolean;
        isDown: boolean;
        isLeft: boolean;
        isRight: boolean;

        constructor(game: Phaser.Game, group: Phaser.Group, x:number, y:number) {
            super(game, group, 'ControlStick');
            this.game = game;

            this.controlField = this.game.add.sprite(x, y, 'hud-control-field', 0, this);
            this.controlField.fixedToCamera = true;
            this.controlField.anchor.set(0, 1);

            var centerX = this.controlField.x + (this.controlField.width / 2);
            var centerY = this.controlField.y - (this.controlField.height / 2);
            this.stickCenterPos = new Phaser.Point(centerX, centerY);

            this.stick = this.game.add.sprite(centerX, centerY, 'hud-control-stick', 0, this);
            if(!this.game.device.desktop){
                this.stick.scale.set(1.15);
            }
            this.stick.anchor.set(0.5);
            this.stick.fixedToCamera = true;
            this.stick.inputEnabled = true;
            this.stick.input.enableDrag();
            this.stick.events.onDragUpdate.add(this.dragStart, this);
        }
        dragStart(sprite, pointerDirection) {
            var deltaX = pointerDirection.x - this.stickCenterPos.x;
            var deltaY = pointerDirection.y - this.stickCenterPos.y;

            var maxPixel = 50;
            var minPixel = -50;
            var threshold = 30;

            if(deltaX > maxPixel){
                this.stick.cameraOffset.x = this.stickCenterPos.x + maxPixel;
            }else if(deltaX < minPixel){
                this.stick.cameraOffset.x = this.stickCenterPos.x + minPixel;
            }else {
                this.stick.cameraOffset.x = this.stickCenterPos.x + deltaX;
            }
            this.isRight = false;
            this.isLeft = false;

            if(deltaX > threshold){
                this.isRight = true;
            }else if(deltaX < -threshold){
                this.isLeft = true;
            }

            if(deltaY > maxPixel){
                this.stick.cameraOffset.y = this.stickCenterPos.y + maxPixel;
            }else if(deltaY < minPixel){
                this.stick.cameraOffset.y = this.stickCenterPos.y + minPixel;
            }else {
                this.stick.cameraOffset.y = this.stickCenterPos.y + deltaY;
            }
            this.isUp = false;
            this.isDown = false;
            if(deltaY < -threshold){
                this.isUp = true;
            }else if(deltaY > threshold){
                this.isDown = true;
            }
        }
    }
}