I love bullet hell games and this was definitely a new twist i loved once i figured out what was going on! the idea that you have to cycle through your weapons to let heat dissipate was really neat idea. One of the things you could have done visually is make the indicator arrow yellow so you could see it better when cycling.
This would be really well rounded out if you had a time survived or a kill score at the end if you wanted to keep this super short. nicely done!