This is XGame, a cross-platform game development framework based on RubyGame and SDL.

You may install rubygame using:

sudo gem install rubygame

or by simply placing it somewhere in your ruby require path.

You may need to install build tools, ruby headers, and SDL
libraries/headers in order to install rubygame.  These should be in your software repositories.

You must also install Chipmunk <http://wiki.slembcke.net/main/published/Chipmunk> in your ruby require path.

To install XGame on your system, just run the traditional:
  ./configure
  make
  sudo make install