Rules.ini
The rules.ini (rulesmd.ini for YR) is the core file of C&C Modding. As indicated by the name, it includes the "rules" of the game, i.e. the properties of every object, weapon, warhead, etc. in the game. This is the main file you're editing when you're modding any C&C from RA to YR. For Generals and everything else basing on the SAGE engine, the INI-system was changed to a more complex, wide-spread one.
Keep in mind, though, that there are two sides of the medal: On one hand, you can edit almost everything in the game from the rules.ini, on the other hand, if you can't change something in the rules, you can't change it anywhere. There's a 99,9% chance that it's hardcoded. (Except, of course, it's art-related. Then you still have a chance ;))
File locations
- RA version is in redalert.mix -> local.mix.
- TS version is in tibsun.mix -> local.mix, the patches add a different version to patch.mix.
- FS version (named firestrm.ini) is in expand01.mix. (This mix file also contains rules.ini, which introduces the generic gameplay changes to plain TS as well.)
- RA2 version is in ra2.mix -> local.mix.
- YR version (named rulesmd.ini) is in expandmd01.mix.