Great game, and the fact that it's open source makes it even better. Bugs don't exist, and the developer is always active, making sure the game is at it's best. As a side project, I wanted to build the .jar from source and the docs on the GitHub made it fool proof. The game itself plays amazingly and is smooth as butter, even on testing some lesser machines.
TL:DR The game is well developed, on top of being an amazing step for open source games,