A very nicely polished game with a heap of potential for further development that I encourage you to do for some of those features from the original concept (particularly an upgradable player). What is there however is still excellent, it is satisfying to destroy the enemies, and there is good variation in the types -- the ufos that lift you up are particularly terrifying. A lot of polish here, you've done well--but would have appreciated a bit more balance as the game tends to get ramp up in difficulty in the same spot a bit too quickly, with nothing the player can do about it without upgrades.