Mine Shaft

It's business as usual down at the gemstone mines... or at least it was, until your trusty mining robots started going haywire and wrecking equipment. Rather than cut your losses, you decide to stick around: can you excavate the crystals from each mine and make a hasty exit before the dysfunctional robots destroy your mine cart? The action takes you down to the twisty network of passageways inside the mine, where several gems are strewn about waiting to be picked up. Soon enough the robots arrive and start running amok, chasing your mine cart along the twists and turns; any contact with them will cost you a life. Luckily (and somewhat unusually, for a mine cart) you're equipped with a gun to shoot them down. When you either collect all the crystals, or hunt down all the errant robots, the exit will appear: pass through it to move on to the next level. You earn an extra life for every level cleared, and the robots in turn multiply and get faster - later levels introduce new enemy types, including the dreaded (and bullet-proof!) skull.