Firstly, I have no idea how to create slider with three items.
Secondly, I tried to look at a lot of different usages and handle some errors, and only after that I started to search about commas between numbers. I understand how to do it, but my code that I wrote will be broken, so It needed me to rewrite whole code, that's why I decided to skip it for now.
And the last thing, I'm not sure on prefers-color-scheme.
Any additional info, links and especially feedback would be very helpful! Have a nice day!
Hi, I have completed the same challenge just today, and I have created the theme slider, You can take a look at code here, may be it help you to build slider.
https://github.com/Aashar-Mehmood/JavaScript-Calculator
and you can view live website here
https://aashar-mehmood.github.io/JavaScript-Calculator.
Regarding your design, The calculator looks too big on large devices, may be set a max-width to container.