UFO shooter

UFO shooter- can you guess what it's about? Go shoot some UFOs, although they may be identified flying objects, so maybe IFO? anyway, shoot the FOs(I guess that's what I'm calling them), beat giant UFO bosses(for the sake of simplicity, I've 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 …