2x0ng version 0.5 has been released for Linux and Windows (Mac versions are in preparation.) This new release includes many changes and improvements, including bugfixes, new music, new sound effects, smoother difficulty progression, improved enemy AI, and more.
2x0ng gameplay video 2 - Indie DB
I hope you enjoy the game, and special thanks to everyone who has given feedback thus far.
Just a note---the jerkiness is only in the video, the real game runs at a smooth 30fps.