Prelude of the Chambered (PoC) is a java game by Markus "Notch" Persson from Mojang.
PoC is an opensource freeware which has been made on Aug 2011 from scratch in just 48 hours for Ludum Dare 21.
This C# port of the original PoC has been created on Aug 2011 by Romain Lods.
peterc has been working on a JRuby port of the game : https://github.com/peterc/potc-jruby
Original game and graphic assets are copyrighted 2011 to Mojang