Any computer program can be designed to run from a single file if you architect it wrong enough! I wanted to create the simplest possible Fediverse server which can be used as an educational tool to show how ActivityPub / Mastodon works. The design goals were: Upload a single PHP file to the server. No databases or separate config files. Single Actor (i.e. not multi-user). Allow the Actor to be followed. Post plain-text messages to followers. Be roughly standards compliant. And those…