This looks pretty interesting, but Cairn is already pretty rules light, so I was curious as to what the major differences are between the two.

The rules and procedures match those in the Cairn Second Edition Player’s Guide, but this version removes the implied setting and structured creation process. It assumes a generic fantasy world, embracing full randomness, much like the original Cairn. It retains full compatibility with Cairn Second Edition adventures but offers an even more minimal, flexible framework for old-school play.