When you get to the Upgrade screen you see the Upgrade button. Clicking on it shows the new quantity selection buttons. Switching between upgrades it does not go back to the single button. When I exit and return it does. Is there a reason to keep the basic Upgrade button? I think it would be better to just show the quantity buttons all the time. When I press Upgrade the first time I expect it to purchase the first one, but it just shows the quantities. If keeping it, it would be nice it the first press did purchase 1. I also will plan to buy multiple and be used to the old system so I'll click on Upgrade twice, planning to buy 2, and perhaps ending up with 11, depending on where I clicked.
I really like the design you have for the cats and upgrades, with the top and bottom bars framing an image. The top and bottom do a great job of giving you place for text that fits the styling.
I got the (non-single use) upgrades up to level 10+, and then let it sit on the side for a while. I think the extra interactions and the effects from them help to keep it more interesting having it just running in the background. There is plenty of movement and things happening. I left it going for a while as I played other jam games. Coming back to buy upgrades and such from time to time. I got the upgrades up to level 100, with a cafe level of 521+. I played around with the mini-games. They work well, and you'll quickly have enough money to do them as often as you want. I certainly like the ability to purchase many at a time for these. It is also nice for the regular upgrades, but especially the consumables.
I don't really have much else right now from this playthrough.