So, from a technical, UI, user feedback and coding standpoint, this is nothing short of impressive. Namely that it was customized so heavily that this could be made in another engine and nobody would be the wiser. The game is focused on shooting and mining, aspects of combat is also done to spice up the mix. You are given stats to upgrade your parameters as you see fit. Once the tutorial is over, you get this massive sandbox of playground you get to play around in, as per the title says.
For what its worth, the overall game is impressive on all fronts and the story, while comedical in nature and a little simplistic with little depth to it, it works as a game of sorts. But let me just say this, this isn't my type of game. And after playing for a while I started to think it was a chore. Namely that this type of gameplay genre isn't something I particularly liked and thus my patience runs a lot thinner than genres I do like, so my impressions do not follow suit with others.
The other fact that you're given no end point (or proper quest direction) makes me feel like I'm just troggling along to the point where I stopped playing at the sandbox area. There is no emotional investment for me to patiently want to finish the game. Hence I had to put a halt to my progress. Stuff like not knowing the number hotkeys until I check the menu and stuff are all on my end, though it does hamper my enjoyment when there's no indicator of what to use. (In addition to all the whole shooting thing and managing skills and resource management.)
Do not take this as a negative, this is mostly me playing something that isn't for me. I respect the amount of effort done to this, no doubts about that. And considering your background, I don't doubt that its a massive highlight of your skills as a programmer (and artistry to some extent as well). Keep up the great work as always.