The original carbon journey game (below), is a paper-based activity that requires printing and setting dice playing pieces for different "reservoirs" and "flux" processes for carbon. For a good background material, read pages 31, 53, and 57 of this lesson plan.
Below is a Scratch online version of the game created by Katherine Johnson NASA IV&V Education Outreach Specialist, Josh Revels.
How to Play the Virtual Game
Discussion Videos
(Watch both after you've played)