Meh...
Sure it's functional, but it really lacks any action. The bulk of enemies are just taken down by standing out of their range and firing into them until they blow up, there really isn't any significant challenge to it. The bosses especially are rather dull. I just think the player needs to get a bit more involved. Add in some more aggressive enemies and/or some more challenging platforming and this could be good, but from what I've seen it's just... meh.