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.
Easy Rider (the big robot, formerly a metal barrel) and
Happy Jack (living in the head of Easy Rider, trying to help him with neurological capabilities) will help and guide the
the player, trying to give some useful hints and guides to solve the riddles.