It’s interesting but the duplicate sets of buttons are a big waste of space. My favourite free calculator app is Desmos Scientific (by the makers of the graphing calculator) [1]. This app gives you as many entry lines as you like and they all remain live. You can also define variables and functions in one line and use them in another. In effect, it’s like a single column from a spreadsheet.
[1] https://apps.apple.com/ca/app/desmos-scientific-calculator/i...