Love the presentation and felt satisfying to play. It took me a little over 2hrs to reach the final depth and have everything upgraded.
The main things I'd like to see adjusted is some of the UI/UX. Having the UI elements covered and the player needing to chip away the rocks is fun to star but having to do this every restart gets very tedious, even more so for the skill tree. I'd also have the skill tree nodes left uncovered as another user said as it can lead to mis-purchasing them.
It may also be a good idea on the cursor to have a point indicating where the exact cursor is. When mining rocks I can see a little + so I know this is implemented however on some menus it was a little awkward at times clicking slightly off as the pickaxe cursor doesn't display the exact click spot.
The talent tree nodes could be spaced apart slightly more as it did feel a bit cramped but that's more personal preference!
A+ job overall