@JamesWeb, as far as I know, whichever bucket you are in, you can always get the versions that contain the editors by appending the “v=b” URL parameter, like: https://developer.mozilla.org/en-US/docs/Web/CSS/background-color?v=b.
I wonder why you see the editors for the JS pages but not the CSS ones, that shouldn’t happen as far as I know.
Yes, the box shadow generator is very nice. There are a few other pages like this in MDN, that are more full-featured, feature-specific tools. I’d like a way for us to make them generally more visible in MDN - they can be hard to find at the moment IMO. Also to keep the source code in GitHub, rather than embedded in the Wiki page .