UFO shooter (owlandwolf)

UFO shooter- can you guess what its about? Go shoot some UFOs, although they may be identified flying objects, so maybe IFO? anyway, shoot the FOs(I guess thats what Im calling them), beat giant UFO bosses(for the sake of simplicity, Ive switched back), play in the normal mode, rush mode with extra enemies, no bosses, and swarms of tiny enemies, or you can challenge yourself to the limit with the near-impossible nightmare mode, where bosses spawn every 2 seconds, enemies cover the screen almost fully at all times, and visibility is low. Then again, maybe stick to a slightly less-challenging bo...