I’ve been looking forward to Marcia’s tidied up version of OD&D. It’s a straight up retroclone: she hasn’t tried to fix the gaps in the game, the gaps are the best part. Enjoy. It’s free!
If you haven’t read OD&D you should, it’s really wild what they thought was enough for people to play a game. And really, they were right. People figured it out and made amazing things.