No goal is a drawback. Anyway, the realization is solid. Only little problem is collision with wall often hinders movement. Oh, and white text on gray walls it hard to read; be careful next time.
However I rated this entry rather high, there is something that bugs me I have trouble to explain clearly. While you have mechanisms (more than the average LD entries) they feel a bit odd. This sounds like a tower defense but without the clear one-path one-goal of a regular TD. While this is interesting to build a TD in a complex maze, if you have no clear goal, all the mechanisms you will add, as solid as they can be, will fall flat.
Sorry for the long comment.
Anyway, overall very good LD entry.