Mr. Do!, that king of arcade clowns, is in a bit of a bind - again! This time, a pack of pesky unicorns is trampling the bricked hallways of his castle.

Help Mr. Do! rid his dwelling of these crafty, quick-changing (and deadly) creatures with the skillful swing of a hammer. Sometimes a quick clobber to the head will do it. Or maybe a well chosen brick knocked out from above. If you can't stop these critters, then break a hole in the floor to slow 'em down. It's up to you to know when to fight - or when to flee! Tension mounts as you hurry Mr. Do! through the castle's maze, grabbing keys along the way. Only when Mr. Do! has collected all the keys can he unlock the castle door, and open up an extra chance to beat these nasty critters!