Sins of a Solar Empire is a 2008 science fiction real-time strategy 4X video game developed by Ironclad Games and published by Stardock Entertainment for Microsoft Windows operating systems. It is a real-time strategy (RTS) game that incorporates some elements from 4X games; its makers describe it as "RT4X". Players are given control of a spacefaring empire in the distant future, and are tasked with conquering star systems using military, economic and diplomatic means.
The game was released on February 4, 2008, receiving positive reviews and multiple awards from the gaming press. Its first content expansion, titled Entrenchment, was released as a download on February 25, 2009, and its second content expansion, titled Diplomacy, was released as a download on February 9, 2010. A package combining the original game with the first two expansions was released at that time, with the title Sins of a Solar Empire: Trinity. A third expansion, the stand-alone Rebellion, was released in June 2012.
A sequel to the game, Sins of a Solar Empire II, was released on Steam on August 15, 2024.
Gameplay Sins of a Solar Empire is a space-bound real-time strategy game in which players control one of three different races: the industrial TEC (Trader Emergency Coalition), the psychic Advent, or the alien Vasari. The playing field is a 3D web of planets and other celestial objects in the orbital plane of one or more stars. The game features a sandbox mode, allowing the player to choose different types of solar systems to unlock achievements. Players can conquer neighboring planets and explore distant star systems in a "massively scaled, fully 3D environment featuring entire galaxies, orbiting planets, clusters of asteroids, space dust and radiant stars." Notably, there is no single-player campaign mode, but games can be played against AI opponents offline and other players online. Ironclad Director Blair Fraser asserted that the game's Iron Engine is specially designed with technologies that allow it to handle very large differences in size, scale, and distance.
Resources and structures Sins of a Solar Empire has three main resources to gather: Credits, Metal, and Crystal. Credits are the general currency used by the three races in the game, and are gained by completing missions, collecting bounties, creating a trade network, and taxing planets. Metal is the most common resource in the game, and is gathered by building extractors on metallic asteroids; it is used to construct basic ships and structures. Crystal is the rarest resource, which can be mined from asteroids like Metal; it is used for developing new technologies and building certain advanced ships. A Black Market feature allows players to convert unneeded Metal and Crystal into Credits or vice versa. Selling or buying too much of either resource can cause market prices to rise and fall dramatically.
Certain more intangible resources include Supply Points and Capital Ship Crews. Supply Points are used up when ships are purchased, and cannot be accumulated, acting as a population cap for the player's fleet. Capital Ship Crews and Supply Points are both required for the construction of powerful capital ships; regular capital ships require one crew, while the giant titans in the Rebellion expansion require two. A player's maximum Supply Points and Capital Ship Crews can be upgraded, but increased Supply Points require more logistical support, imposing a permanent reduction on the player's income.
Players can construct planet-based infrastructure upgrades and orbital structures on and around habitable planets that they control. Planetary upgrades grant bonuses such as higher tax incomes, better planetary bombardment resistance and access to more orbital structures. Orbital structures are divided into civilian logistical and military tactical structures. Logistical structures include asteroid mines, ship factories, trade ports, research laboratories and cultural broadcast stations. Tactical structures include orbital weapons platforms, repair centers, strike craft hangars, and superweapons unique to each playable race; for example, the TEC can build the Novalith Cannon, a giant railgun capable of bombarding distant planets.
Entrenchment and starbases The Entrenchment micro-expansion adds new defensive options. Defensive weapon platforms and strike craft hangars gain researchable special abilities, and all factions gain the ability to deploy proximity-detonated space mines. The expansion's most notable aspect is the addition of starbases – immense defensive structures with significant firepower and various special abilities.
Celestial objects and anomalies There are multiple types of colony-supporting planets and asteroids, with the expansions and later downloadable content increasing the available planet types over the years. Habitable worlds range from Earth-like Terran planets to frozen Ice planets and water-covered Oceanic planets, with some planets possessing random bonuses such as enhanced factories or better defenses. The player can interact directly with planets in several ways, such as creating trade routes, raining destruction from orbit or spreading "culture" via propaganda platforms, which may cause enemy planets to revolt in the player's favor. In addition, there are pirate bases, which are abnormally durable and well-defended asteroids that have no resources but provide a boost to tax income.
Furthermore, there are several different spatial anomalies (more commonly known as uncolonizable objects) found in the game which serve as obstacles and hazards to all players. These include ice and asteroid fields, which reduce weapon accuracy; gas giants, which can cause dangerous explosions if a ship is destroyed nearby; stars, which allow for interstellar jumps but have large gravity wells that are slow to traverse; and various forms of space junk, which do not affect ships directly. Wormholes link some systems, and once the necessary technology has been researched, they can be utilized for instant travel. In addition, DLCs have added traveling hazards such as plasma storms, random rebellions, economic downturns and coronal mass ejections.
Neutral forces, known as militias, guard and may own colonizable planets not occupied at the start by any of the players. Their forces are an assortment of TEC frigates, cruisers and defensive structures. They do not venture outside the gravity well, but will attack anything owned by non-militia forces that enter their gravity well. Pairs of pirate ships sometimes similarly "guard" uncolonizable gravity wells.
Diplomacy and bounty The diplomacy options of the original game allow players to forge and break alliances and place bounties on their enemies or allies (depending on the game setting) without anybody knowing who placed it. Players can trade resources, establish trade routes between empires, manipulate the commodities market to hinder enemies by utilizing supply and demand, and issue optional "missions" to allies.
Most planets are "guarded" by neutral TEC fleets, who will attack anyone that ventures near; this is especially true for the Pirate Base planets, which are settled by pirates and are heavily fortified. In the game's start-up screen, players can also choose to enable "Pirate Raids". This mechanic allows players to anonymously place "bounty" on other players, with the goal of inducing the pirates to attack that player. The more bounty is placed on another player, then the larger the attacking fleet will be if the pirates choose to attack that player; pirate raids also gain strength over time, and to deal with them, the player has to find all the pirate bases, which are the spawn points for raids in their respective star system, and wipe them out. Pirate forces are, with one exception, TEC frigates, cruisers, orbital defense platforms, and mines (and the only exception still bears a similarity to Trader ships), but they are all unshielded, have heavier armor, often have their armament switched to autocannons, and are heavily customised with spikes and stylized holographic "Jolly Rogers". Rebellion also has voiced responses for pirate units (which can often found in the service of TEC Rebels).
Sins of a Solar Empire: Diplomacy expands upon the Diplomacy mechanic. The relations system is more visible, and players can give missions to each other, as opposed to the original's NPC-only mission issuing. Diplomatic envoy cruisers can be used to further improve relations, and the researchable pacts can significantly strengthen both sides of the alliance. The expansion also sees a noticeable increase in pirates' strength, and their bases are now outfitted with mines and TEC-issue repair platforms and strike craft hangars.
Tech tree and artifacts In the base game, each faction has two technology trees, divided between military and civic improvements. These two trees in turn branch off into three race-specific categories. The Military tree contains upgrades to armor, shields, and weapons and unlocks units and defensive structures. The Civic tree contains upgrades to resource gathering and unlocks civic buildings, PSIDAR (Phase Signature IDentification And Ranging, which allows incoming enemy ships to be detected), planetary upgrades, diplomacy upgrades, and terraforming. In Entrenchment, several elements of both trees, as well as new elements such as starbase-related technology, are merged into the Defense tree. In Diplomacy, the diplomatic elements from the civic tree, as well as new technology that focuses on upgrading the race's diplomatic Envoy cruiser and various other bonuses, are merged into the Diplomacy tree. The Rebellion expansion grants additional unique technologies to each sub-faction of the three races.
There are many different hidden artifacts that can be found by exploring colonized planets. There are a total of nine (twelve in Entrenchment) artifacts, each giving the owner a unique and powerful bonus. For example, an alien artificial intelligence can increase economic efficiency across the player's empire, while an ion field technology can fortify planets against attack. When an artifact is discovered, all other players are notified of its location but not its type.
Units There are five main categories of ships in the base game: capital ships, strike craft, cruisers, frigates and civilian ships.
Capital ships are large, powerful vessels and the cornerstones of any fleet; they can gain experience in combat and "level up" (to a maximum level of 10), thus unlocking new abilities. Each race has five different classes of capital ship (six in the Rebellion expansion), including battleships, support battlecruisers, colony ships, strike craft carriers and heavily armed dreadnoughts. A player's first capital ship is free, but subsequent capital ships cost large amounts of resources. In addition, each capital ship requires a large amount of Supply, and one Capital Ship Crew.
Strike craft are small, agile ships that launch in squadrons from capital ships, carrier cruisers and hangar-defense structures; they are divided into fighter and bomber classes. Fighters are strong against bombers, other fighters and frigates, while bombers are strong against cruisers, orbital structures, and capital ships. Strike craft do not require any resources to construct, and cannot travel through phase space unless carried by their mother ship.
Frigates are small, cheap and, individually, weak vessels that fill basic combat and reconnaissance roles, including long-range support, planet-bombing, and the colonization of new worlds.