This book brings together several related exercises in game design. The game of Tetrad itself is the product of an effort to devise a simple game of abstract strategy for four players . . . . The Tetrad board was designed with several considerations in mind: to provide a layout well suited to a four-way game, to accommodate a wide variety of traditional games, and to be compact enough to fit on the cover of the book. . . . The TETRAD playing field consists of 120 octagonal spaces arranged in an octagonal pattern. This pattern is printed on both covers. The game is played on one side of the closed book. The playing pieces and dice are stored inside of the book. The game of TETRAD is designed to be played by exactly four people. —description from the book Each player begins the game with six pieces of the same color. These are arranged in a row along one side of the board. At the center of the board is a group of four spaces. These are each marked with a symbol. The objective of the game is to group four of one's playing pieces at the center. The first player whose color occupies all four of these spaces at the same time, wins the game. The players take turns casting the dice and moving their pieces. A player begins a turn by casting the two dice. The score of the dice is the total number of steps that the player's pieces may be moved in that turn. One step is the movement of one piece from one space into the next. The pieces can be moved vertically or horizontally, but not diagonally. Moving your piece onto a space that is already occupied replaces your opponents color with your own. The TETRAD board can be used to play many other games; instructions for various and adapted games are included in the book. —user summary