RuneScape
I don’t personally play it anymore but it having still players to this day and thriving proves it.
Edit: On second thought it’s probably Java Edition Minecraft. Thing spawn an industry around it. Now people’s livelyhood depend on it. A generation learning java programming just to make plugins or mods. I bet this also what increase the number of java developers. Probably inadvertently also introduced to Blender. Being accessable and sandbox made that possible.
The prisoners themselves are the tune. They would be electricuted if they go out of tune. This is recorded for all the viewers to see.