Doppelgangers is a four player map in Sins of a Solar Empire consisting of 4 stars and 32 planets.
Official Description: Four empires have laid claim to a star system a piece. When venturing out to conquer a neighbor, be wary - things are not as familiar as they seem.
Tactics: Each player's star system is fairly easy to colonize before other players can jump between stars and attack. Once the AI start exploring into your system, place almost all of your forces on your home star. There, they have a very fast antimatter charge up rate and can attack enemy ships as soon as they warp in. On its way across the star, the AI ships will not defend themselves at all, and your squadrons are safe. Stars are good places to focus all your ships on one enemy capital ship.
The disadvantage to the one star per empire arrangement is that any empire can go straight to yours- they are all only one star jump away.