Like many open source games, it has that distinctly 'alpha' feel to it right now, but I do enjoy NodeCore on occasion. It's a zen minimalist block game with a unique diagetic crafting system. Instead of a traditional "recipe book" or "crafting grid", you produce new materials through in-world transformations. For instance, to make glass, you have to surround sand with fire, and to control fire, you basically want to build a deliberately-shaped dirt or stone pit... the whole thing feels a little like minecraft and a little like a sand physics sim or cellular automata.