I'm not a fan of idle clickers, but even then the game should try adding some animations that show what spamming the 0 btn is actually delivering.
What do I mean by this ?
1. when the player spam clicks the 0 btn there's a bar that fills up as long as you're in the job screen/menu but buying a CPU doesn't change anything except a just number.
2. there should be a function in the game whenever you buy something you're redirected to a page where you see that the upgrade has brought in a new change to whatever you're upgrading.