GraphicsDeviceManager graphics;

。。。。。。。。。
  /// <summary>
        /// This is called when the game should draw itself.
        /// </summary>
        /// <param name="gameTime">Provides a snapshot of timing values.</param>
        protected override void Draw(GameTime gameTime)
        {
            GraphicsDevice.Clear(Color.Transparent);  
            
            base.Draw(gameTime);
            if (splashScreen.Enabled)
            {
                splashScreen.Draw(gameTime);
            }
        }

            GraphicsDevice.Clear(Color.Transparent);  的效果是背景是酒红色，不是透明的。