Taking advantage of the GBA's processing muscle, Fortress adroitly mixes a Tetris-type puzzler with strategy and action elements. Choosing one of four themes (cavemen, medieval, pirates, outer space), you build a fortress by placing geometric shapes.

The catch is that your human or CPU-controlled rival is also building a fortress. Once you're done building, you can place weapons, which then shell your rival's fortress. Of course, your rival is attacking you, too. By cleverly placing tetrads, you'll be able to activate monsters that will attack your rival or rebuild your own fortress. Fortress exploits the GBA's wide screen, since you build a fortress that sprawls sideways toward your rival's.