The squares falling in the background are proportional to the amount of money you get, there's just a limit to the amount of squares to decrease lag. And if you think it's getting boring the circlepocolipce is a background changer. 3 new background types! And in update 1.7 coming out on thursday there will be even more. If you want though in update 1.8 maybe I will add some color changes that you can get through upgrades, being added in 1.7!
I'm glad you enjoy the game and like calculating what shop item is the best deal at the moment! There will be much more to come and comments like this really help the game! By the way if you get to the point where you want to update Time Warp it will glitch and update Space Driver instead, the fix will come in update 1.7!