Just for the sake of listing, what "alternatives" are available today ? I can think of
1. Codepen (pure HTML+CSS+JS+frameworks)
2. jsfiddle.net/ (pure HTML+CSS+JS+frameworks)
3. Cloud 9 (full ide?)
4. https://anvil.works/ (pure Python)
5. CaptainDuckDuck ?
6. Repl.It
8. Runkit.io (pure node.js)
Other ?