I don’t really see any websites that allow you to practice webdev skills asides from JS. Maybe ask the user to make like a project or a simple website with the things they want implement and have them rank it and stuff?
Small update: So I found something that may help you out a bit. It’s a resource with 40 challenges (code is provided if you choose to look at it) for different effects.
URL: https://blog.bitsrc.io/40-html-css-projects-for-beginner-2021-5bd01ff62361?gi=119d34df83af
There’s a lot in here that I haven’t experience in producing on webpages, so I may use it when I feel inspired to take another crack at it. Still not a Project Euler, unfortunately. Most people seem to just freestyle their web development to gain experience and practice.
Again, I apologize if this isn’t quite what you’re looking for.
