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