With the advent of antibiotics, platinum credit cards and thermal underwear, the purist's notion of natural selection remains a long-forgotten, useless ideal -- at least until the aliens attack. Sequel to a 2002 Half-Life mod, Natural Selection 2 will act as a survival-of-the-fittest simulation for both sides: Players will inhabit the bodies of aliens and Marines to see which traits will be passed on to the following generations. We're guessing large teeth and precise trigger fingers will make the cut, but not necessarily on the same species.

Natural Selection 2 is set to launch this summer, but those who pre-order will get early access via the beta on Steam.