Basically, the square box is you, a warrior. Your job is to find a stolen chalice and return it to the yellow castle where you start from. You need to cross multiple screens and find several objects to help you, such as a magnet, a bridge, a sword, and several keys which will unlock several castles. However, you can carry only one item at a time, and there's an annoying bat that flies around and can steal the item you're carrying. In addition, there are three ducks -- errr, dragons -- that will try to eat you, and they can chase you across the screens, so be on the lookout and find the sword. There are three variations of the game. The first is the easiest; it has only two dragons, no bat, only one maze, and two castles. Good luck with the other two games.
The graphics are completely lacking in pizazz as mentioned before). You'll just have to convince yourself that the square box is you, and the duck-like figures are menacing dragons. However, the chalice is programmed with rolling colors, which is nice. Likewise the sound consists mainly of blips and beeps with no in-game music to speak of. The most interesting part of the game takes place in the corridors. They don't seem to have been designed correctly, because you always seem to wrap around when you leave the screen.
This game has historical importance (aside from being the first console 'quest' game). Atari wouldn't let give its designers credit for their games, so Robinett decided to hide his name in Adventure. To find it, you have to find an invisible dot and carry it to the room where you started. (If you need help, the main part of this website has a handy dandy map for you to use.)
The game may not look like much, but don't let that stop you from picking up the joystick and slaying those dragons. Adventure is very enjoyable for gaming adventurers, even if you're not into history.