I am happy to hear that you found my comment helpful. If you need more feedback, I can only say that you should put the music in replay, so it doesn't suddenly stops. With walls, I meant like building who could hold the ghosts (and spiders), like cheap (probably wood based) buildings, who would stop the enemies, and make them nice target for towers. Also, probably, make the starting castle able to shoot, so it doesn't get too complicated with trying to expand away from the spiders.