I like zefquaavius' "holistic summary" of the rules for Daybreak [1]. They've published a bunch of others games rules in this form too [2]. They're not sufficient to learn to play the game but are absolutely perfect for remembering the details of how the game works after you've learned once.

1. https://docs.google.com/document/d/1blJZCDK2A8DC6f6akcCcQ9_M...

2. https://boardgamegeek.com/geeklist/190653/holistic-summaries...