Calculator App - HTML + CSS + JS, tried to focus on accessibility

Please try it out and if there's any errors please let me know so I can fix them. Copied most of the behaviour (when it comes to input, display and navigation) from Windows system calculator. I tried to make it accessible so keyboard navigation can be used (numbers + operators or use arrows to navigate keypad). Color themes can be switched with keyboard too. However! I found out that NVDA screen reader hijacks arrow keys however so things don't work as they planned, and overriding that seems counter productive. I also checked with Thunder and while the navigation works fine, it doesn't read out much - but I've only just installed it so haven't had much time to get used to how it operates. Lots more to learn I guess :)