Mr. Do's Castle for the Atari is based on the arcade game created by Universal in September 1983. The Asian title of the game is Mr. Do! versus Unicorns. Though marketed as a sequel to the original Mr. Do! released one year earlier, the game bears a far closer resemblance to Space Panic. It is the second of the Mr. Do series of video games, although it wasn't intended to be. It began life as a game called "Knights vs. Unicorns", but the U.S. division of Universal persuaded the Japanese arm to modify the graphics into a Mr. Do! game, taking into account the first game's popularity.
The object of Mr. Do's Castle is to score as many points as possible by collecting cherries and defeating unicorn-like monsters. The game takes place in a castle filled with platforms and ladders, some of which can be flipped from one platform to another. The player controls Mr. Do as he collects cherries by using a hammer to knock out blocks that contain them from the various platforms. Empty holes left by the knocked-out blocks serve as traps for the monsters - if a monster falls into a hole, the player can then defeat it by causing a block above the monster to fall on top of it. If the player takes too long to complete a level, the monsters transform into faster, more difficult forms that occasionally multiply. The game advances to the next level when all cherries on the level have been collected or all enemies have been defeated. The player loses a life if Mr. Do is caught by a monster, and the game ends when the player runs out of lives. The game is an example of the trap-em-up genre, which also includes games like Heiankyo Alien, Lode Runner, Boomer's Adventure in Asmik World, and Space Panic.
The Atari 8-bit version of the game is particularly hard to find. Ours has the cartridge and manual but no box.