We’ve been busy working on technical documentation to share with you on best practices for Custom Content and Mods and details about how the game works. We’re happy to announce that this can now be found here: TS4_Custom_Content_Guide.zip
The Sims 4 is a large game, so we can’t document everything about it, but we’ve included information about a few key things we thought you’d appreciate.
We hope this accelerates your progress. Please continue to ask questions in the forums, and we will do our best to answer them.
For updates and discussion see that thread and/or the sticky in Modding Discussion – locking this one so we don’t have two parallel threads.