Mine Shaft

The Good
The gameplay is standard arcade fare; you can shoot to protect yourself against the mine robots while trying to collect the gems and reach the exit. This is easy to pick up and learn.

The Bad
The mines that you have to navigate are generated completely randomly, which would normally be a good thing because you'd never play the same mine twice. But a particularly nasty behavior of the mine creation process can create some very tight diagonal passages, which are incredibly hard to navigate through because the game doesn't process diagonal controls. The bad guys can navigate these tunnels effortlessly, of course. This is unfair.

The Bottom Line
Use this game as a demonstration of how cartridge games work on the PCjr, but otherwise avoid it.