Here is My fantasy game post Swords& Wizardry the retro clone of OD&D.
There are three versions all of them good and differing in complexity.
White Box this is a basic 1974 Role playing simple rules small rule book needs lots of Imagination. Not a bad thing because I started with OD&D back in 1974 OK so I am old.
the next part of the S&W line is the Core rules this is D&D with the supplements and some more mechanics
than we come to Complete this set is a retro clone of the best of the first seven printings of the original rules.
I use all three sets for different game groups and each works well. There is a reason for these posts that I will make clear a little later.