In year 20XX, aliens came to Earth to invade us humans. Instead of showing massive artillery, they sent viruses to infect and kill all populations. A few people could hide themselves in caves to prepare for counterstrike. Scientists created NanoMechas to fight infections from within the contamined people.

Thanks to http://www.nintendomax.com/viewtopic.php?t=12386&f=54 for the news.

http://www.eviltroopa.com/