This is MaK (pronounced "Make"), an upcoming game from indie outfit Verge Game Studio. Primarily a "third-person physics sandbox game with an action focus", it's based around the idea of building, customising and moving around some tiny little planets.
Which means, yeah, you can build stuff out of blocks, but because the game's got a complex physics engine you can also create more elaborate devices like weapons, circuits and even vehicles.
All of which sounds, and looks, pretty damn promising. MaK has a Steam Greenlight page, linked below, you can check out to help get the thing off the drawing board and into people's hands.