It is now hard to find CDs of the game, but the PC version is still sold as a download. The game is still played online, and one group of fans has developed a patch, which fixes some bugs and adds more game set-up options, and a few mods which adjust the game balance. The as-sold version of the games sometimes does not run correctly under Windows XP or Windows Vista, but running it under the control of DOSBox is a reliable approach, and also has advantages for playing online against human opponents.
Master of Orion II offers three ways to win - defeating all opponents; get elected as the supreme leader of the galaxy; or lead a successful assault against the homeworld of the Antarans, a vicious high-tech race. There is a wide range of planet types, most of which can be improved by terraforming. The best planets are usually guarded by space monsters, which present a severe obstacle in the early game, when fleets are small and low-tech. The game features 13 pre-defined playable races and allows players to produce custom races. The race design options include abilities that enable specific races to be much more productive on certain types of planet than a "standard" race. Managing an empire's finances is an important part of the game: buildings have maintenance costs, and an empire can be ruined by running a large fleet without having enough starbases, which are expensive to build. The game presents an extensive technology tree to research, and players can also acquire technologies by trading, spying, planetary conquest, or capturing and dismantling enemy warships.
At the start of a game players choose whether space combat should be "tactical", controlled by the player, or "strategic", controlled by the software; but choosing strategic combat prevents players from designing their own ships and disables certain technologies which the game's AI would be unlikely to put to decent use in ship design or combat; "tactical" combat offers an option for the software to take over the current battle. Attacks on enemy colonies can aim either to destroy them or to invade them; invasion is the more expensive but offers long-term economic, technological and strategic advantages. Diplomacy is also important in single-player games against AI opponents, but is often forbidden in online contests between human opponents.
The game can include random events - lucky breaks, disasters or emergencies which are not caused by the player's actions - but these can be disabled in the game start-up menu.
The user interface is mainly mouse-driven, but some screens also have hotkeys for important functions. Players can manage their economies almost entirely from the Colony List. Other screens provide information about the capabilities and diplomatic relationships of enemy empires.
Some time after the start of a game, the Antarans, breaking out of the very prison dimension the Orions have banished them to long ago, begin sending increasingly powerful fleets against players' colonies, simply to destroy rather than to invade. The only way to stop the Antarans and their campaign of terror is to carry the battle to their home universe through the Dimensional Portal.
Despite the game's name, conquering the Orion star system does not automatically win the game.
You can colonize all types of planets, but they vary in several ways, making some more desirable than others:
The most desirable systems are usually guarded by space monsters, much less powerful than Orion's Guardian but still a severe challenge in the early game, when fleets are small and low-tech.
You can change a colony's output by moving colonists between farming, industry and research, except that natives can only farm. You can research and construct buildings which improve a colony's productivity in one or more of farming, industry and research. These game elements came almost directly from an earlier Simtex game, Master of Magic.
If the gravity of a planet falls outside of the gravity range your race is accustomed to, productivity is reduced, but you can research and construct a building that remedies this.
Pollution is a serious constraint on industrial production in the early game, but you can research technologies which reduce or eliminate it (all but one of these technologies require new buildings).
Maintaining buildings costs money and so does running an excessively large fleet. All colonists pay a standard tax to your treasury and in emergencies you can set a higher tax rate, but this reduces industrial production. You can also improve cashflow by researching and constructing certain buildings in larger colonies. You can use surplus money to accelerate production at selected colonies, but not to increase agricultural or research output.
Ships of different sizes require different numbers of "command points", which are provided by orbital bases, which are major construction projects for small colonies. You can research technologies which increase the command points provided by orbital bases. An empire can be ruined financially if its fleet requires more command points than its orbital bases provide, because "buying" extra command points is very expensive. This severely limits the size of empires' fleets; before you research technologies which increase the command points provided by orbital bases, you can have only one frigate (smallest type of ship) per starbase or one battleship (largest type of ship in early game) per 4 starbases without having to "buy" command points.
Each technology area is divided into several levels, each of which contains 1 to 4 technologies. You can only research one technology at a time. To research a higher-level technology, you must first have researched the previous level.
"Creative" races get all the technologies at a particular level by completing one research project at that level; most races must choose only one technology from each level; "uncreative" races get no choice and the game software randomly selects a technology for them at each level. The way in which technologies are spread around the tech tree reduces the risk that an uncreative race will be left in a completely hopeless position, but looks rather odd.
Players can also acquire technologies by trading, spying, planetary conquest, or capturing and dismantling ships.
The "Races" (diplomacy) screen also enables the player to allocate spies between defensive duties and spying or sabotage against other empires.
Players can design warships, provided they choose the "tactical combat" option in game set-up. One can design a maximum of 5 classes at a time, but can have an infinite number of classes in operation.
One can refit ships to take advantage of technology improvements which do not provide free upgrades.
Ships can travel to any star system within their range, unlike games such as Space Empires or Ascendancy where interstellar travel is possible only via "wormholes". Hence in Master of Orion II you cannot create easily-defended choke points.
Space combat occurs in two types of location: in orbit over a planet you are attacking or defending and on the outskirts of a system if one side is driving away the other's blockaders. It is impossible to intercept enemy ships in deep space. Limitations on the size of empires' fleets (command points, see above) mean that most battles involve only a handful of ships on each side. Ships do not stack, but move and fire individually.
At the start of a game you choose whether space combat should be "tactical" (controlled by the player) or "strategic" (controlled by the software); but choosing strategic combat prevents you from designing your own ships. In tactical combat the screen has an "Auto" button which makes the software take control of the player's ships and finish the battle. In practice, a human player can usually manage the combat much better than if he uses the "Auto" option, so that option is usually used for those combats where the outcome is not in any doubt. Since combat takes place on a two-dimensional map, and vessels cannot be "stacked" or placed on top of one another, it can be annoying or tedious to advance every single vessel into firing range, and the player may use the "Auto" option to automate the movements of his secondary and/or smaller units. Pressing the "Z" button on North American keyboards results in an "Auto" software controlled battle, but at immensely increased speed and featuring no graphical animations at all, an option for use in battles towards the end-game, where huge armadas of very advanced warships may take upwards of ten minutes to completely destroy each other. As with the "Auto" option, this is usually used in situations where the outcome of a battle is unambiguous, but the player does not wish to wait several minutes for a battle to unfold, even with the game's artificial intelligence taking a minimum of time to decide and execute each move.
You can only invade planets when all defending ships, orbital bases and planet-based defenses have been destroyed or forced to retreat. In order to invade, the attacking fleet must include some troop transports, which will be lost if the invasion fails, and at least one will be lost (deployed on the planet) if the invasion succeeds.
You cannot control ground combat: the result depends on numbers, ground combat technologies, racial ground combat bonuses, and some Leaders (if present), but you see a display which shows the progress of the combat and the ground combat technologies and bonuses used by each side.
Recently-invaded colonies are disaffected and have poor productivity, but slowly improve, and there are ways to speed up the improvement. There is also a risk that recently-invaded colonies may rebel and rejoin the empire which founded them, which can be managed with certain buildings or having extra troops on the ground.
Instead of invading, you can destroy enemy colonies. This is cheaper in the short run but invading has longer-term advantages if successful: you may steal a technology; the newly acquired colony extends the range of your ships; the colony will contribute to your economy and research. Other options include taking the planet but exterminating the population gradually (an non-option for democratic empires), allowing the conquering empire to import their own loyal citizens or manufacture a robotic replacement workforce (once the requisite robotic technology has been developed or stolen), and gassing a planet with bioweapons, which do not damage valuable buildings, but which kill troops and population, making the colony easier to take by invasion. Usage of biological weaponry incurs a substantial diplomatic penalty with most races. Late in the game, highly advanced empires may also completely destroy planets with Death Star-like energy weaponry, an option which deprives enemies of valuable real-estate which may be under contestation if the player is incapable of defending it. This is a desperation measure, and is almost never utilised outside of situations in which the player would be incapable of utilising the planet themselves.
Telepathic races (see "Playable races") can mind-control enemy populations instead of invading with troop transports; but mind-control is thwarted if the defending system belongs to a telepathic race or is governed by a telepathic leader. Telepathic races also assimilate conquered populations instantly, without a period of disaffection or risk of rebellion.
Each player starts with 10 "picks" (race design points). Choosing advantageous traits reduces the number of picks available, while choosing disadvantages increases them, but you cannot choose more than 10 picks' worth of disadvantages.
Most of the options are easy to understand: major or minor advantages and minor disadvantages in farming, industry, research, population growth, money, space combat, espionage and ground combat.
Races from high-gravity homeworlds are fully productive on high-G and normal-G planets, and only mildly handicapped on low-G worlds; low-G races are severely handicapped on normal-G planets and practically helpless on high-G worlds. In ground combat, high-G races have doubled hitpoints by nature, while low-G races get a minor disadvantage in their combat efficiency.
"Creative" races research all the technologies at each level by completing one research project; all other races must choose one technological application to develop out of a given research project; "uncreative" races get no choice and the software randomly selects an application to be developed out of each research project undertaken. "Creative" is the third most expensive option, and typically confers greater advantages the longer a given game lasts, due to the fact that there exist technologies to modify and enhance almost all abilities and aptitudes (as such, a race with every technology researched by the end-game point can generally outperform all other races in their own specialisations).
"Subterranean" races have a higher population limit on colonized planets, and have a bonus in ground defense.
"Tolerant" races have a higher population limit on colonized planets than most other races, and their industrial productivity is not reduced by pollution. This is one of the two most expensive options.
"Aquatic" races have more productive farming and higher populations on "wet" planets (Tundra, Ocean, Swamp, Terran) than other races. Note: although quite a lot of types of planet are "wet", at the start of a game the great majority of planets cannot support farming at all.
"Lithovores" feed on the natural minerals of a planet, and do not need to farm. This is one of the two most expensive options.
"Cybernetic" races need half as much food as non-cybernetic races, but each population unit also "eats" half a unit of industrial production. They can also repair ships during combat from the start, while other races must research Automated Repair Units and install them in their ships (reducing the space available e.g. for weapons) if they want their ships to repair themselves during combat.
"Transdimensional" races travel through space a little faster than other races at the same propulsion technology level. They can also travel through space (very slowly) without researching any ship drive technology, or when all interstellar travel is otherwise prevented by a hyperspace flux.
"Charismatic" races receive a large advantage in diplomacy, and more opportunities to hire leaders and at lower cost. "Repulsive" races have disadvantages in diplomacy and in choice and cost of leaders. Repulsive races cannot form alliances, sign treaties, or do any diplomatic contracts aside from declaring war, surrenduring, and suing for peace.
Telepathic races have advantages in diplomacy and espionage, and can also conquer planets by mind control when they have overcome the defenses, instead of having to use troop transports to invade. Mind-controlled populations are instantly assimilated into your empire. Telepathic races also can instantly control captured ships and starbases in combat. Thus optimal in conjunction with the cybernetic trait.
Omniscient races can see all planets and ships (even those with cloaking devices).
"Fantastic traders" do better out of trade treaties than most, and make double income from trade goods.
Lucky races get more favorable random events than most and far fewer disasters or emergencies, and tend to be overlooked by marauding Antarans.
Warlord races have the advantage in space combat and defensive troop production and produce command points per colony.
You can also choose your empire's form of government, which has almost as much influence on how it performs as the choices described above, but the "best" governments cost a lot of picks. Dictatorships are the most common governments for the pre-defined races, and cost no picks. Democracy provides major advantages in research and money, but is the most vulnerable to spying and sabotage. Unification government provides advantages in farming, industrial production and spy defense but does not benefit from morale. Feudalism provides a large reduction in spaceship construction costs, but suffers from very slow research; the race design menu treats it as a significant disadvantage. Each government can be upgraded once by research, but the upgrades mostly increase the advantages of each without decreasing the disadvantages.
As a result of the wide range of choices, quite a lot has been written about race design for Master of Orion II.
This is mainly mouse-driven, but some screens also have hotkeys for important functions.
The main screen consists mainly of a zoomable (not scrollable) map of the galaxy. Stars have names which are color-coded to show which empires have colonies round them. Clicking on a star that you have already visited produces a pop-up window which shows the planets round that star. Clicking a fleet allows you to give orders and displays a pop-up which shows each ship in the fleet. Dotted lines show ship movements. The buttons along the bottom give access to various menus. The icons on the right provide information about the status of the empire and access to additional menus.
Players can manage their economies almost entirely from the Colony List, which can be sorted by any of one of: Name, Population, Food production, Industrial production, Research production, the item currently being built, or Cash (BC) generated. The Colony List allows the player to access any colony's Build Menu, and to change a colony's output by moving colonists between Farmers, Workers and Scientists.
The Build Menu allows the player to queue up to 7 items (buildings, ships or spies) for construction at a colony, to refit ships in that colony's system and to design ships which may then be built at any colony.
At the end of each turn Master of Orion II shows a report in which items link to the appropriate display, usually to a colony's Build menu when a construction project has been completed.
The Information menu gives access to: a History Graph which shows how the player's empire compares with rival empires; the racial characteristics of all empires with which the player is in contact; the technologies the player has researched; and descriptions of all technologies, including the exotic ones which the player cannot research but may gain by beating Orion's Guardian or by capturing an Antaran space ship and scrapping it afterwards.