This was fun.
The normal levels were kind of hard as you need to get through the enemies to the exit (rewarding getting to it).
However I think I cheated on the Boss lol: You can stand just before the spawn and just keep shooting from there. The bullets will kill everything that spawns and they will also get to the boss and damage it. And killing the mobs gives you more bullets, so if you match your shooting with the spawn, then you never run out of bullets. So I’m not sure if I cheated, or if I broke the system! lol