This is like 3 minigames melded into one! That feature adds balanced variety and longevity to the game, while seamlessly retaining the theme of the game.
I found that the graphics could use a bit of improvement, namely the UFOs have boxes around them instead of being rendered with a transparency mask. It does make them easier to target and hit though! Besides that, the graphics could use increased consistency, meaning the style of the graphics could be more consistent (i.e. some graphics look cartoonish, while other adjacent graphics look life-like and almost photographic). Unless that was the intention, to "collide" or "superimpose" two distinctive styles of graphics clashing together.
Nice job making this game. It is simultaneously both challenging and fun to play, which is not an easy feat to accomplish.