Official guide for game mechanics?
Game mechanics evolve over time. This is the way. When kits change, the in-game kit description is updated accordingly. When a game mechanic changes, we get a dev post and/or update release notes. ...
Forum Discussion
The honest truth for me is Discord. There are a lots of great servers with people who have a fantastic knowledge of the game mechanics. It is where I have the most interesting conversations about SWGOH.
