Mr. Do!'s Castle is an arcade game released in 1983. It is the sequel to Mr. Do!. It was ported to the Atari 2600, the Atari 5200, and the ColecoVision.
Mr Do!, the clown, moves around six floors interconnected by ladders -- some fixed, some whose top can be pushed left or right. The clown is armed with a hammer that is used to knock out floor stones. Some are marked with a cherry, collect all these to finish the level. The unicorns (baddies) fall into holes that you knock into the floor. Some fall through and survive, whereas some get stuck in the holes. If left they will climb out, leaving a block in the hole, and become nastier baddies. The way to kill the unicorns is to knock a block from the floor above onto their head. When all are killed, the level is complete. The hammer can be used against them, but merely pushes them away a little. On the nastier ones, this does not work at all! There are sections of floor marked at each end with a skull block, which when both skull blocks are knocked out, all the blocks fall to reveal 'wooden floorboards'. Good for killing multiple monsters! There are three blocks in the floor which contain keys, knock them all out to open the doors at the top of the screen. Behind it is a shield, which when collected, turns the unicorns into Alphamonsters. The Alphamonsters flee from Mr. Do!, and can be killed with his hammer or by knocking out a floor stone onto them. When you kill an Alphamonster, its letter appears on a flagpole at the top of the screen. Collect all five letters to obtain another Mr. Do!
The ColecoVision version was originally developed by Coleco.