The patent for this game was filed in 1982 by Charles F. Reed, and granted in 1984 (US patent number 4,470,602). Two players each have six cubes with the sides colored in three different colors (opposite sides matching). One color is "vulnerable," a second color is "blocking," and a third color is "aggressive." Each player's six cubes are alike, but some pattern distinguishes one player's cubes from the other. On a three by six horizontal rectangular grid, each player's cubes start with "vulnerable" on top all along the nearest side and "aggressive" on the left and right sides of each cube. In turn, each player rolls or tips one of his/her cubes up to two spaces, possibly including an orthogonal turn in the middle. If a piece started the turn as "aggressive" it can capture by landing upon an opposing "vulnerable" or "aggressive" piece as any part of this move. No piece may move through a "blocking" piece. Adjacent captures are mandatory. The first player to capture or immobilize all six opposing pieces wins. A necessary house rule to avoid fortress defense stalemates is to only allow vulnerable pieces to move two spaces.