3 1/2 stars = Very good
Ratings explained

There was nothing quite like "Sins of a Solar Empire" when it was released two years ago, and there still isn't.

The game has been frequently tweaked and rebalanced, and has seen two "micro-expansions": the defense-oriented "Entrenchment" last year, and now "Diplomacy." All three elements are packaged together in the new "Sins of a Solar Empire: Trinity" (Stardock; PC; $39.95; Teen). (The expansions are available piecemeal, although "Diplomacy" requires "Entrenchment" to play.)

The game is still about establishing an empire of many planets with one's chosen faction (the money-focused human TEC, the culture-dominating cyborg Advent and the overpowering alien Vasari) and collecting the resources to build mighty fleets of ships that can lay waste to worlds -- and each other -- in fantastic-looking space battles.

With this add-on shoring up its last game-play weak point, "Sins of a Solar Empire" feels complete. As the name suggests, "Diplomacy" adds new ways to interact with others, human or computer-controlled.

There's a new option for diplomatic victory: A player who amasses enough diplomacy points can win the game that way.

Each faction has a new diplomacy technology tree that allows it to research envoy ships that can visit other factions' worlds and improve relations with them, among other things.

The new tech trees feature a variety of other research options, some aimed at directly improving the player's standing with other factions, others at giving or taking resources, still others at manipulating pirate raids further than simply bidding on the next attack target.

The diplomacy menu in earlier versions of the game was a simple affair, with a basic indication of a faction's opinion of the player and a window for any missions they wanted the player to undertake. Now it contains a display that lets players track their relationships between all players at a glance useful for deciding whom to attack or aid, and who might offer help or send a fleet to invade.

With the right research, players can select a task (such as destroying a certain number of ships or structures belonging to a player) and specify a reward in credits, then make the offer to a rival.

Completing missions increases factions' standing with each other, allowing them to eventually make valuable new pacts that provide substantial mutual benefits to both allies.

-- By Justin Hoeger McClatchy Newspapers

Doug Oster writes a blog, "Growing With Doug," exclusively at PG+, a members-only web site of the Pittsburgh Post-Gazette. Our introduction to PG+ gives you all the details.