I wish there were an option to auto-complete the maps that you bought. They're the best way to upgrade your weapons but having to click on them over and over again is not much fun.
My one critique about this game is that since all items are picked up at the end of the match there should either be no drops in the actual fight, or they don't get picked up at the end. There's no reason to have both there.
On one level I had a skeleton that was invincible, and one of the green leaping things that was stuck on the edge of the map. Couldn't finish the level because of that.
This game would be a four, but for a few small issues. The rocks can't be destroyed by shots, and your enemies can shoot through them. Makes it very difficult to actually beat the game, even with full upgrades. As well, the souls take up too much room on the screen and you can't see the enemy shots. As well, it's very difficult to know what your hitbox actually is, some way to clarify that would be nice.
Yes, we are fixing this for the next version!