Better layout on small screen

**Is your feature request related to a problem? Please describe.**
In split screen, the layout (buttons position) is not usable and it missing the basic operations (add, times, ...)

**Describe the solution you'd like**
A perfect solution would be to adapt the layout according the size of the app (responsive).
Another alternative would be to hide advanced operators in small screens (root, modulo, ...)

**Describe alternatives you've considered**

**Additional context**
I use a lot the split screen to show, at the same time, a logic game and this calculator.