In idle mining you made a lazy forever option in the form of a demonic stone. Now you have this demonic bench. This game only has 3 upgrade options.
Is this a test or a game?
The best part of idle games is the flavor text and unlocking new options to play with.
Flesh it out, you have a missed opportunity here to do some funny cho-aniki style graphics here.
Why not add some mini games or make the supplements appear more often.
The code is solid but the game is weak.