Okay about the UI...
The rolling text on buttons is very annoying, please remove that function.
That goes for rolling text on what each thing do.
When you get an achievment it take up space so you can set the Buy button for Donut shop which is very annoyingm especially in the beginning when you earn a lot of achievments fast.
Add a label so you can see how much money you have, and how many angels you have when you are buying upgrades.
Add a scrollbar and add function so you can use scrolling wheel on the menus.
I personally liked it better when you didnt have the go through all x1, x10, x100, use one click on the one you want, not cycle through them.
I also think the menus need a redone, 1/3 of the screen is for a header or description often. When i click on for example upgrades I want to see upgrades, not a big fancy header.
Some images on menus seems to be scaled down which results in pixalted images instead.
it's a great idea... and it's in the next version.