You are a block. You grab a yellow arrow and point it into duck-looking dragons. You grab an "H" without the middle bar and you can walk through walls. You open gates of castles with keys and get lost in mazes in order to locate a flashing cup. When you bring back the flashing cup into the yellow castle, everything blinks and it makes firework-like noises. There is also a hidden dot that will allow you to pass over the sidelines and read the names of the developers.
Ahh, my favorite Atari game.