An abstract strategy game for 2 to 6 players created by John Cooper. It's played using Icehouse pieces.
Briefly: Homeworlds distills the experience of playing a classic "4x" space-empire game like Master of Orion into a chess-like game small enough and simple enough to be played on a pub table. Even more briefly: It's space chess. Homeworlds looks and feels like the kind of game you'd see starship captains playing in the background of a science fiction movie.
Icehouse pieces are small, plastic, multi-colored pyramids sold by the Looney Labs game company as a kind of "open-source board game". Like a deck of cards, these pyramids can be used to play many different games. They used to sell Icehouse sets in "stashes", plastic tubes which contained 15 pyramids of the same color: 5 small, 5 medium and 5 large. More recently, the pieces were re-marketed as "Treehouse" sets that contain 15 pyramids in five different colors: 1 small, 1 medium & 1 large for each color (plus a special die and rules for playing a newer game called Treehouse).
To play Homeworlds, you'll need at least 3 Treehouse sets, and 5 sets to play the classic four-to-six-player game. (The traditional four colors are red, blue, green, and yellow, but any four colors will do.)
Each color represents a different technology, which governs the basic actions that you can perform (green: build, blue: trade, yellow: move, red: attack). Pyramids placed upright are star systems. Pieces placed on their side are spaceships, with the direction they're pointing indicating who owns them. All of the pieces come out of the same "global stash", introducing an ingenius element of resource scarcity.
Each player begins with a "Homeworld"-- a binary star-system containing two stars of any size & color-- and a single spaceship. If your two home stars are destroyed, you lose. If at any point you don't own any spaceships in your home system, you lose.
There are three major variations of the game: "Classic", "Sinister", and "Binary".
In Classic Homeworlds (3 to 6 players), each player is secretly given an "alignment" card at the start of the game, either Good or Evil. The goal of the Good players is work together and eliminate all the Evil players. The goal of an Evil player is to work alone and eliminate any other player (Good or Evil, doesn't matter). Since the alignments are secret, Evil players must lie in order to stay alive.
Sinister Homeworlds works just like Classic Homeworlds, except that it removes the Good-vs-Evil mechanic entirely. Instead, your goal is to destroy the player on your left (and, inversely, not get destroyed by the player on your right).
Binary Homeworlds is simply the two-player head-to-head version of the game. For Binary Homeworlds, the global stash is reduced from 60 pyramids down to 36, allowing "stash control" to play an even greater role in the overall strategy.
Andy Looney, the guy who invented Icehouse, now calls Binary Homeworlds "my very favorite Icehouse game". Perhaps not coincidentally, he's also the reigning champ of the game, having won the official Binary Homeworlds tournament at Origins Game Fair in '05, '06 and '07.
Complete rules for the game can be found online at IcehouseGames.org. You can also play the game online (for free!) at SuperDuperGames.org.