This is a real winner from Stateside and as such should carry health warnings since it is likely to keep you up all night and severely tax your blood pressure and patience.
You must guide Rockford underground searching for Jewels and avoiding falling rocks which have a habit of crushing him. If you collect enough jewels and find the exit, you progress to the next level.
It's not as easy as you think since it is easy to end up squashed or trapped. There are sixteen caves with five skill levels. You can start at any one of five caves. Each has different features and you must develop new tactics for each. Some screens behave differently each time. After four screens, there is a playable intermission, but I can't comment on these since I haven't managed to reach one.
The graphics are first class and the animation and movement of rocks are positively Newtonian. This game surpasses all of its genre and is in a class of its own. This is a must for your games collection.