It had to happen: in-chat multi-player #Quake III Arena #webxdc app, running over @n0iroh and using the fine work of https://ioquake3.org/ folks. Quake3 app is 1.2MB but you need to download once a game file of ~50 MB. It's only one level.
Realtime-P2P-networked multiplayer gaming arranged through securely end-to-end encrypted email, from a group chat!
Both Quake3's in-game chat as well as game play messages have forward-secrecy. What a weird future, eh? :)
Screenshot of in-game quake with a player looking down on a situation where a rocket launcher just exploded.
screenshot of an in-game quake situation where the player just "fragged Holga, 1st place with 16" (kills)
A screenshot of a Delta Chat group chat where a quake3 webxdc app is posted, showing the Quake logo, and there is a "start button". Wofwca (the author of the quake webxdc app) immediately is ready and joins the game. A short while later there are three people from the chat playing.
screenshot of Quake app at https://webxdc.org/apps/#wofwca-quake3