Go nutz and beat the crap out of everything.
This is the export version of one of my entrants into 8bitrocket's 16KB Retro Remake contest. I've always been disappointed that the oldest games are always about shooting and not breaking faces. I look at them and shout "How hard could it have been to break faces in the 1980s???" The answer: not very. :Earth Zone isn't very long, but there will be sequels that are longer and harder, because everything should get longer and harder.