The ending threw me off-guard haha! This is very neat, but I do have some slight criticisms. For one, you should make the XP gained based on the amount of bullets that hit the boss rather than the amount of damage dealt because damage upgrades are also basically XP upgrades. Additionally, the ground tiles are nauseating at high speeds (which can be fixed by making the tiles bigger). Other than that, this was fun. I especially enjoyed the boss' bullet patterns - they felt fun to dodge :)