Players compete to uncover a secret code consisting of three elements, each of which may be one of four colors. They do this by taking actions determined by the roll of three Treehouse dice. Rules for this game were initially released in July 2007 as part of the 3HOUSE booklet; it is played using three complete Treehouse sets. It is unrelated to the Icehouse expansion of the same name released in 2000.

In pre-release, this was called "Secret Project 3H-1".