Notrium is a survival game where you can pick from one of four different bodies: human, alien, robot, and psionic, and where you have to survive on a planet by being resourceful, by hunting for food, energy, and other resources, and by combining items you find. The world appears to be randomly generated, and the difficulty is very high (even on easy mode). There also appear to be a good variety of interesting mods for it.
FAQs / Walkthroughs
Here is a FAQ I found.