Wonderful game. There's a glitch in the "Assorted Player Pack", however. On level three, if you fail to land on the black square in the lower level to shift to the door, you have no choice but to restart. If you do, your man is permanently locked into the lower level by checked blocks and you can't continue.
Giving players the ability to replay at the bosses would be very much appreciated. It is incredibly frustrating to be defeated and have to replay the entire level over again.