Patterns: building and exploration in a world of triangles, physics, and more triangles
Patterns lets you play a man made of triangles as he combines triangles into non-triangle shapes to build mega structures like some sort of mad triangle god. It's being developed by Second Life creators, Linden Labs in partnership with Free Range Games. It'll let you "explore caverns and valleys, while you harvest substances with real world densities." You can use those harvested substances to construct
the greatest triangle in the universe bridges and the like.
There is a beta, which you can sign up for on this Linden Labs page. Linden Labs CEO Rod Humble provides a visual introduction to the world of patterns in this debut trailer.