I got fed up with all these complicated calculators and re-implemented the original Mac calculator desk accessory at https://CalculatorDA.com.
It does the simple things I need while giving me a nice nostalgia buzz.
I have been carrying around a copy of the Windows XP calculator ever since Microsoft decided that nobody can do both decimal values and decimal <-> hex <-> binary conversion without having to go through a menu to change modes. With the XP calculator, I use F5-F8 as shortcut keys for changing bases whenever I want. The Windows 10 calculator doesn't even do anything with those keys in scientific mode.
Thanks! That story was part of my inspiration. I gave my Calculator DA a lot of visual toggles in the View menu so you can find your way to the look that makes you happy, like Steve did.