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.
This contains file contains the data of the mod. Extract it and place it in your sourcemod folder under your Steam installation. Then restart Steam. You will find the mod under S.T.T.&R. in your game list. Have more information in the release guide in this download section and have fun playing this mod.