This is an example of a game built with metro, a library that gives structure to gosu (the 2D game development library in Ruby).
gem install metro
git clone git://github.com/burtlo/starry-knight.git
cd starry-knight
metro
This is a near duplicate of the tutorial that you create at the end of the ruby tutorial for gosu. However, if you look at the structure of this project you will find distinct differences and that is because it is using metro to take care of a lot of the tedious coding tasks.
NOTE: This state of the game, as is the Metro library, under active development, so it is possible that some of the information within this README is inaccurate and has not kept pace with the latest developments.