Well worth the asking price (and then some) just from the hour and a half I've played so far. Solid concept, well implemented, and just a lot of fun to figure out. A few rough spots which would be nice to see cleaned up, but for $4 it's impressively well put together.

EDIT: Dev has been very responsive to feedback (my own and from others) and done an amazing job of improving the game even beyond its initial state. Not the most complex and involved game, but a lot of fun and very well priced for the content!