Style Alertbox / notification popup Woocommerce

Hello everyone,

Curious if you guys do style the default ugly unfriendly alertbox / notification popup from Woocommerce or Wordpress that you get when the visitor for example does not select a variable for a variable product. Then you get a warning in the alertbox telling the visitor to make a choice.

I used some ancient code snippet that doesn’t work anymore in certain browsers (with certain extensions) and if it did work the alert was acting as a popup and could be ignored (with alertbox you need to click ‘ok’ before you can continue).

Would things like https://alertifyjs.com/ be a good option or is there an easier option with some new code snippet and basic css styling?