Swaps all of the units and visual effects around so that all three factions can be played. The balance changes included in the mod address numerous long standing complaints about the original game while the faction swap provides a fresh experience to the gameplay. The mod has been built from scratch with full compatibility on all maps and missions in mind: Any map that worked with the original game will work with this mod. The campaign can also be played either as it was in the original (with the new balance changes included), or by using the previously inaccessible Terran units instead.
Here we can see some of the new Terran weapon effects coming in Version 3, although these still pictures don't really do them justice.
Nice, but how can you make changes like this? I thought its hard to mod GC2, because theres no tool for it.
Massive released a SDK (Software Development Kit) for the game after it came out, in there are a whole host of tools for editing the game data. A few unfortunate items (like factions) are still locked away in the source code though. Making new weapon effects like this was actually pretty simple once I figured out how the code for them worked. The SDK does come with some pretty good documentation, but particle values is not included in it.
I've uploaded the SDK here on moddb because finding it through search engines has become something of a pain: Moddb.com