Valve continues to put in some nice packages for pre-ordering upcoming games from its Steam download service. The latest is for Multiwinia, the upcoming multiplayer strategy game from UK based Introversion Software. From now until September 19, people can purchase the $19.99 game and receive Darwinia for free.

Darwinia, which normally also costs $19.99, is basically the earlier single player version of Multiwinia which has an somewhat retro art arcade art style as you control strange sprites in an odd computer generated world. Multiwinia has these sprites battle each other for control of the world in six different game modes. Introversion is selling special editions of the game at its web site.