Stack-Up (also known as Robot Block and simply Block (ブロック, Borokku?) in Japan) is a video game released in 1985 for the Nintendo Entertainment System, designed for use with R.O.B. the Robotic Operating Buddy. Stack-Up is one of two games in Nintendo's Robot Series, the other being Gyromite (AKA Robot Gyro). While Gyromite was a pack-in game with the R.O.B. itself and therefore came with all the parts needed to play the game, Stack-Up came in a large box containing additional bases and colored discs. Because it was marketed to children and the set came with many small, plastic parts, complete copies of the game are very hard to come by. All Stack-Up cartridges contain the 60-pin circuit board from the Famicom version attached to a 72-pin adapter like the T89 Cartridge Converter for the NES, causing a number to be dissembled. This is one of the rarest first-party games for the NES.