Very nice! It has a good vibe to it.
I played the web version (https://itch.io/embed-upload/16150683) in Firefox. I had no issues with the bookshelf.
I was never fast enough to get more than two gems on any of the minigames, and I was never *slow* enough to get *fewer* than two gems. That was true even when I had never seen a minigame before and was still figuring out how to interact with it.
One note: At the very beginning, the Manager says, "Nice job! Hey, i can already see our first visitor." But the first visitor is not visible at this point. After you dismiss the dialog, there a short delay before the first visitor appears outside the building, where they are visible to us, but still not yet visible to the Manager. So I was pretty surprised by the dialog. (Also the "i" should be capitalized in that message.)
I really liked the way you could see the effects of the upgrades in the behavior of the customers. The music was nice. There was very little stress, but it kept you engaged. It was nice. Thank you.