I've written a tutorial for creating a platformer game using Ruby and libgdx. The repository with the tutorial and the project assets is here: https://github.com/kabbotta/LibGDX-and-Ruby

Let me know at 08kabbotta80@gmail.com what I can do to improve it. I will most likely be adding a section on using the Universal Tween Engine along with libgdx and Ruby in the near future.