I hope you are still working on this game. it is quite fun for me. i found something that may make it significantly more playable for other players. it seems that the bullets are causing the game to lag over time. i have done a few tests and during level 10 you notice it the most. if you have a single bullet it will almost always hit a target. once you have a split of 3/5/7 bullets some of them don't hit a target. i believe that you are experiences an instance overload where the bullets are still processing outside of the playing field. if you dont already have this setup, please add it. make 4 boxes on the outside of the playing area. call these edge or deadzone or something like that. when the bullets collide with the boxes, they will destroy themselves causing no damage to anything. i believe this will help the playability of your game and allow user to go much further past level 10 without the game lagging so much. you can test this by intentionally gaining bullet shot speed and bullet splitting. keep damage as low as you can. the more bullets you have per second in level 10 will show you the lag. do it again and dont split the bullets just focusing on speed alone. limited damage increase to make it through the level but just enough to kill things relatively quick so you can see that the monster instances are not the overload factor in level 10. I hope this helps, the game is fun and has potential .i hope to see an unlimited level game in the future. great job!