The premise is clear: people try to destroy the Halloween spirit of a haunted house, but the monsters won’t let it happen — a simple, but also strong idea which also fun. Core of engagement are finding the effective combinations and abilities / features of enemies and other creatures.
When you made the house in the sub-spaces / rooms, that is something unique and special which not seen yet in tower defense games. You could been use this feature in the game much more - for an example, monsters wander around in the room creeping out whoever interact with them, and some of the intruders dares or manages to get through in the next space.
Reminds "Bloons TD meets Plant vs zombies with some classic halloween spirit" - but also I think this is an interesting title by it's own too. A little bit too much retro style (one-by-one intruders, lack of animations/effects/sounds, and so on), but characteristics still works nice and the concept is actually very ideal.