Sludge is an official skirmish map from Supreme Commander.
Sludge is a small map where space is at a premium; the small islands mean you will never have enough room to build all of the structures you want to, but the 12 mass points on each island mean that mass is usually not a problem. Sludge puts a heavy reliance on naval units and defense. Land Factories are useless on this map and Air Factories are not recomended. Naval factories are recommended since they don't use any of your limited land space, and navel units are the key to victory since they can freely move around the map. Nuke launchers, Tech 3 Artillery, and most Experimentals are too big to be built on this map unless you are willing to build experimentals underwater. Stealth tactics are only useful early, since a Omni radar will cover the whole map. Your commander is the key to your success on this map. Upgrade to tech 3 as soon as possible so you actually have room in your base for the buildings you need. Remember, build fast and build smart. You don't have room in your base for mistakes. Battleships are often game enders on Sludge, since they are able to attack from behind your island and still hit the other two. Once another player has battleships you have at most a few minutes before your island is levelled.