While staring at the keywords documentation in the standard library, it occurred to me that an interactive playground could be a really effective way of explaining/teaching Rust's syntax.
This is barely a proof of concept, it needs way more work to be 100% reliable, but I think it looks neat enough to show around. (Mobile is kind of funky, though)
Very nice concept... I think it could extend to be quite powerful, eg it could inline documentation instead of putting a link, eg. like in an iframe, and it could actually do so for everything and not just syntax, just using docs.rs and the docs of the stdlib to provide docs on everything.
One can also imagine it working as a browser extension so that when reading code on github you could turn it on and get all the docs right there... exciting!