I think at its core this is a good game, but there are some issues. However, most issues have pretty easy solutions I think: There really needs to be some instructions in the game of what the goal is and how the mechanics work, because as it stands you just get thrown straight into the action and have to figure everything out on your own in a pretty hectic environment. I'd also like some visual indicator of when you hit enemies, as right now you can't even tell if you hit them or not until they die. It would also be nice with some kind of minimap or radar system to let you know where all the enemies ares, as the arena is quite big and you sometimes have to spend a lot of time at the end of each level just roaming around trying to find the last few enemies. Related to that, it would be great with a clearer indicator of when each level completes, because if you're not near the middle of the arena you can't really tell if the level is done or not.
On the plus side, the game has a good challenge level and pretty good enemy variety that requires you to approach them in different ways. With some more polish and even more enemy variety I think this could be really fun.