Needs feedback from the game. Something like a bar that empties when you manually mine, and fills up over the cooldown.
The first manual mine needs to also trigger on click AND/OR needs something to draw attention to it in the first few seconds (red arrow with a circle should work).
Needs tooltips or some other way to show what the heck does each upgrade do.
Needs to work while not in focus.It's really bad for an idle game when it has to be at least somewhat on the screen in order to passively gain currency as it practically shuts down the entire monitor from active use.
Also yellow text on green background is evil. At least use a black shadow.
Good work so far.