Very cool, love the atmosphere and the mix of 2D and 3D, the mining and improvements feel really satisfying, amazing sound design also. It all feels really immersive and i would consider buying a commercial version of this if it came combined with more of a story and a deeper progression system, just something to break up the main gameplay here and there.
I was unable to further upgrade anything on the right-hand-side after a while, despite having lots of money, and don't know if this was intentional or a bug - i kept playing to try and be able to do that so if it's intentional, maybe that could have been better communicated. Loved this, really good job.