TREG is a game for training in Requirements Engineering, specifically in the Workshops technique. It was created in Second Life using its building and scripting possibilities. This works presents an exploration in the use of a prototyping process and techniques for developing the game. The prototyping process of the book Effective Prototyping for Software Makers is an iterative process which was customized for the development of the game in this virtual world. Branching Stories is a simulation genre that gives an overview of all the possible paths the player can take in TREG. Scenario is a Requirements Engineering technique used for the specification of the simulations modeled in the Branching Stories graph. The design of TREG used the Scenarios specifications for modeling the software perspectives. The state machine diagrams shows the dynamic behavior of the TREG objects, a class diagram represents the objects created in Second Life and the communication diagrams shows the relationships and the flow of messages between objects. This work also shows the results of the evaluation made and the difficulties presented by the participants whereas TREG was used.