Stack-Up (JP: Robot Block) is an early platformer game for the Nintendo Entertainment System. The player directs Professor Hector to jump onto buttons, each of which activates an action for the Robotic Operating Buddy (R.O.B.) accessory. A given sequence must be followed in order for R.O.B. to arrange the colored discs in the correct order on the five pedestals surrounding it. Stack-Up is considered to be a rare game, especially outside of the USA, with the discs being among the hardest to find accessories for the NES.
Like the other R.O.B game Gyromite, the game uses a series of screen flashes to tell R.O.B. what the player wants him to do.