Looking for: Shared real-time code editing and execution that's web-based

I’m looking for a safe way for strangers to collaborate over code editing in real-time (multiple cursors) and execute it in a controlled environment with minimal fuss.

HedgeDoc combined with glot.io
Google Docs combined with codepen.io

I don’t know of any services that combine those but i’m looking to produce a guide to give people options for collaborating on the fly so they spend less time stuck on the how. I’d like people to be able to jump into different projects as-when they can to help out or code in parallel.

This’d be partnered with Jitsi / Mumble / Matrix / Discord VOIP.

Ideas very welcome.