Tunnels & Trolls, also known as T&T, is a fantasy role-playing game designed in 1975 by Ken St. Andre and published by Flying Buffalo. It was the second modern role-playing game ever published and was developed to be a simpler alternative to Dungeons & Dragons and as a game which would be suitable for solitaire and play-by-mail games.
The 5th edition was first published in 1979 and remained unchanged until 2005 when the 5.5 edition was published. The 5.5 edition added about 40 pages of new material, the majority of which is the Buffalo Castle solo adventure. The mechanics of 5.5 are the same as 5.0 and material written for one edition can be used with the other with little or no modification.