The ghosts are attacking your castle! Fend them off as long as you can. Just use your mouse to aim, and click to fire. Sorry for the lag... ALSO: The cannon needs to reload! There is no need to spam the mouse button; it is reloading. Once the ghost stops moving, it's dead. Even if it is still on the screen, it's dead.
This does have a lot of lag. This uses a couple of variables, but I have very limited knowledge of them, so try and look past the errors...