Got stuck on the third level because I couldn't find the key to get to the next one. I can only assume it's because I didn't buy the suit to mine harder objects. In these kinds of games, I always upgrade the items that make it go faster first so I can breeze through my way to the other items. But by the time I mined all the minerals in the third level (and in the two before it), I didn't have the money to upgrade my suit. I didn't think that would be a problem because I assumed I would be able to level up/upgrade the way I wanted. But clearly the key was behind one of the walls I couldn't mine. I even went through and mined all the dirt in every level for good measure just in case. This game has great potential, but I wish I was able to upgrade the way I like instead of needing to upgrade the suit first and not finding that out until I've played for about an hour. Maybe I'll come back some other time and restart with the suit upgrade first, but I'm too frustrated right now. I will not be getting that hour back.