Calculator App with VanillaJS

I learned a lot about CSS variables and how to switch what values the variables have when working on the color picker. I also learned a lot about edge cases and thinking of every possible issue that may arise. Although I believe I found them all, please let me know if you find any. I also challenged myself to build the keypad using JavaScript instead of html. However, I ran into issues because I wanted each key to have a separate class related to its name (i.e., del-button, reset-button, etc), but given that some keys are already used for other functions in code, it was difficult to accomplish. Is there any better way to go about this?