When Maxis made their EPs and SPs they included a new collection file (the little folder in buy or build mode) for each new EP they made. But they did not think in retrograde, they needed to also include a collection for the base game. Since I wasn't able to find any base game collection files, I decided to make my own. The Maxis icon is the buy mode collection, the EA icon is the build mode icon.
Attention Custom Lot and CAS Builders! You will still need to say that EPs are required if you created your lot or CAS with those EPs installed, even if you used only base game content!
