Played for a decent amount of time. I have to say, pretty good game. But there are always improvements. Here are mine:
1.You should put a timer to make the game more challenging. Also can be a gamemode. It would have the player to be more alert when making upgrades, mining, etc.
2.Put more workers. 3 is not enough. If thats not good, then put more upgrades to the workers to make them more efficient, make them work faster, etc.
3. Make some things cheaper. I am having trouble working had enough to get one upgrade. So, you can also put upgrades to make things cheaper.
4.More needed upgrades and less unnecessecary upgrades. You can put more upgrades like a faster energy refresh or things like that. If you dont like that, you can put more buttons.
Those are all my reccomendations. But, 4.5/5