public Engine(int width, int height, string assetsDirectory = "./")
: base()
{
MP.Width = width;
MP.Height = height;
MP.currentWorld = new World ();
Window.AllowUserResizing = true;
graphics = new GraphicsDeviceManager (this);
graphics.SynchronizeWithVerticalRetrace = false;
graphics.PreferredBackBufferWidth = MP.Width;
graphics.PreferredBackBufferHeight = MP.Height;
graphics.ApplyChanges ();
this.IsFixedTimeStep = false;
//graphics.IsFullScreen = true;
//graphics.ApplyChanges ();
Content.RootDirectory = assetsDirectory;
Engine.currentEngine = this;
}