I used this calculator app for years since I have used RPN since the introduction of the HP-35 calculator. This version is now locked in light mode when my phone is, whereas it used to look like the current dark mode. Also, we in the US use a . For the decimal point. So, I suggest you (1) allow the user to pick dark or light mode from the app settings, and not tie it to the phone’s overall dark/light setting, and (2) allow the user to specify . or , as the decimal point indicator. As far as function, this app works great as a replacement for my worn-out HP-41CV.