Boulder Dash

I played Supaplex as a kid and I didn't know it took its formula from here. It's a really fast paced game that truly leaves no space for error, especially in some of the later missions where you'll need some dead-on timing, provided you already charted out a plan on how to beat the level. You collect jewels underground by digging tunnels, making sure you don't succumb to boulders or accidentally trap yourself. Later on you'll find enemies which are grevious annoyances, but it's an immersive experience, with plenty of levels requiring eye-widening lateral thinking.

It's only 16 levels long, and it is easy enough to manage with some save-states.