Game Help:Core Mods
What is a core mod?
One of the various types of hacks available for Sims 3 is core mods. These are usually big mods, which change a lot of things, specifically features of the game and the way the game looks or works, as opposed to changing less complex things like objects. Examples of core mods are AwesomeMod, Indie Stone (discontinued) and Extended Game Core (discontinued).
Because of their complexity, core mods need some special attention when you're downloading and using them. There are a few things you need to remember.
Core mods will only work for the patch level they were built with! You should always update all your hacks when you patch, as very often a new patch will be incompatible with a hack. However, as you have probably noticed already, some smaller mods often don't need updating, or will work for a couple more patches even if they're not updated. This is not the case for core mods. Core mods always need to be the right version for the patch.
Remember that this also means that you can't use an updated core mod in a non-updated game! Remember also to clear your caches when you update mods.
You can only use one core mod at a time! The way that core mods work is by replacing a handful of very big game files, called the core files. If you have two core mods both trying to replace the same core file, your game won't work. This is essentially the same as a normal hack conflict, with two caveats: because there are only a few core files, whereas there are lots of other game files, core mods are more likely to conflict with each other than normal mods; and whereas a normal hack conflict may only cause some annoying bugs restricted to one part of the game, a core mod conflict will cause much more serious problems - basically, it will break everything.
In actual fact, this rule - the "Highlander" rule - is a bit of a simplification. Some core mods can be used together, because they happen to replace different core files. However, don't assume that this is the case for all core mods! Usually, core mod creators will state on the download page which other core mods their mod can be used with: if you can't find that information, be cautious and ask.
What problems can occur with core mods?
There are several problems which can be caused by improperly used core mods.
If, when you start your game, all you see is a black screen, then you have conflicting core mods. Pick the one you want to keep, and delete the other one. If you need help finding the mods in your Mods/Packages folder, see:
In-game controls don't work
If some of the options in Live mode, Buy/Build mode or CAS just don't do anything when you click them, then you have an out of date core mod installed. One common culprit is Rez Delnava's CAS skintone UI mod, which causes this problem since patch 1.17. Remove or update the mod.