One of my favorite games of all time is a little-known gem called Silhouette Mirage, a game made by Treasure, which was originally released for the Sega Saturn in 1997, but only in Japan.

In 1998, the game was ported to the Playstation, and one year later it was released in North America. The game is similar to Contra in gameplay, in that it is a platformer and you shoot enemies with a variety of magical powers. The game takes place in a post-apocalyptic Earth where every living creature has mutated into beings that are known as Silhouettes or Mirages.

The idea here is that the society is split in two, as the two attributes repel each other. The plot implies there is a civil war brewing between the two factions on the planet, but it never really goes past it being casually mentioned.