Steam, Tracks, Trouble & Riddles (S.T.T.&R.) is a single player adventure mod, based on source engine (Orange Box) by Valve. It combines two types of game play: an adventure game with complex, 3D-interactive riddles in a fantastic environment and a simulator for track based vehicles.
Here some early drawings of the mod concept: Some vehicles are shown you already have seen, modelled and implemented in the mod. Some have still to be build for chapters to come.
Some of the vehicles won't be build, because they didn't made it to the final concept.
And there are some character concepts. I consider to implement them,
if i can find the time.
"Jack on track" looks quite likeable actually