> Writing the GUI part of the program should not take more time than the actual functionality
I don't understand why this is a rule. I mean, I don't know what the author is trying to build, but in general the GUI is the part that the users spends all of their time interacting with. I don't see why it would be a problem if a little more time was spent there.
Also, in my experience, writing UI code is usually more(!) work than writing the functionality underneath, because
a) styling / layouting has to be learnt from scratch (e.g. because of a proprietary language, e.g. QML or QWidgets for Qt)
b) you have to take care of every frikkin' single user interaction (which becomes worse the more dynamic and custom your UI is), and building proper accessibility is also no walk in the park
I don't understand why this is a rule. I mean, I don't know what the author is trying to build, but in general the GUI is the part that the users spends all of their time interacting with. I don't see why it would be a problem if a little more time was spent there.