Since that version You can play against aside from own Relax chess engine also against any UCI (eg. stockfish, komodo) chess engine. Just with one click You can select the engine or change it even during the game !
Other changes include much faster game thanks to much better performance of human moves (now You can play even faster the computer).
Also the clocks run now as Swiss ones guaranteeing the equal chances for both parties.
You can try the trial versions available for (Windows or Linux), or purchase one (Windows only).
Try it out http://22.214.171.124