Fun game. Runs very smoothly and I liked how the upgrading is randomized. As mentioned by others as well, it was fairly easy for me. But I can definitely see how with more enemies and bosses etc. it becomes more challenging. If this is not already the case: maybe make the enemies faster the longer you take to level up (and reset that on level up) so it is encouraged to pick up experience even more. Also it would be nice if there was a way to pause the game. (unless I missed that)