By the end, we were quite pleased with what we'd managed to put together!
Alterations in the code ensured we could generate and display a maze of good size, despite early setbacks.
The controllers worked out just fine, giving a much better interface than the pushbuttons we used for testing, although the B button signal occasionally doesn't fire on the first try. We think the problem is with the controller, but it's not too much of a distraction, since B is only used in initial menu navigation.
Adding in the 'monsters' and 'keys' to our initial specifications was what really made the game. After finding out the limits on maze size imposed by the SRAM, the maze by itself was too quickly run to be much fun, and making smaller mazes no longer made any sense as a 'difficulty' adjustment. Possibly being chased into a corner by a monster just before you get that last key on level 6 makes sure that there's challenge enough to make the game interesting.
Two-player co-operative mode works well, and prompted much laughter when one or both players failed to escape.
The scoring system tracks progression mode's high score across chip resets, providing additional incentive to making it to the elusive Level A.