Not a bad game...but there are some flaws. The biggest flaw that I see is fuel. I mean when you're dropped on the surface you're told to fill up--which I do--then I start mining...I don't go too deep...yet I always run out of fuel right before I get to the surface. What I would consider is making the starting fuel tank bigger, lessen the fuel consumption rate at the beginning and maybe having the helicopter thing that you use to get to the surface not use up your fuel. It's kind of hard to get any kind of upgrades when all you're doing is refueling.
Also, I find the fact that if you run out of fuel you explode and die (how you can explode with no fuel is beyond me.) kind of annoying...I'd make it so you'd have "lives" if you run out of fuel you sit idle for a few momnents and your pod refuels itself--perhaps it converts what minerals you have into fuel--and you'll loose one of your "lives". It would make this game a little easier and I think a lot more playable.