Yes, this is the good-old game that even is a difficult challenge to everyone who plays it - Digger!
You have to control a digging machine in a mine and collect emeralds and gold while you evade nobbins and hobbins, the minemonsters who are coming to get you! Your goal is to collect all emeralds in the mine, or to kill all nobbins or hobbins. When it's done, you go to the next level, each level becomes harder, of course. There are also gold bags, which fall and cruch everything under them, including you, if you are not paying attention. However, these bags are very useful to crush minemonsters below you, and if they fall two or more spaces, the gold falls out from the bags and you can collect the loot. Also, there's the bonus cherry. If you have killed enough (4; in the first level, 3) monsters, you get the cherry, which if you collect, you can eat the monsters and get big scores for a small time.
The gameplay is pretty interesting. You control the digger with the arrow keys, and shoot with the F1 key. There are usually four monsters opposing you. After getting periodically 20,000 points, you get an extra life. Levels get harder and harder - more emeralds to collect, faster nobbins and hobbins, hobbins remain hobbins for a longer time, slower fire recharge rate, less bonus time, etc.
You think it's too simple? Bah! This game has one of the best artificial intelligence I've ever seen! Here, all the monsters work as a team, and they'll most likely surround and get you, or they work together to become hobbins for a larger chance. It's extremely hard to dodge them.
You need a genuine CGA card or...
...you need to set the machine string to 'machine=cga' at the DOSBox configuration file to play the game. The recommended CPU cycles are 450 to 500, or else it will be too slow or fast.