Gameplay of StarCraft

The central objective in any StarCraft (multiplayer or single player) game is to defeat opponents (human or computer-controlled) by overpowering them, usually by destroying all of their buildings. Some single-player missions and custom maps feature different objectives.

Race asymmetry
Starcraft is a strategy game based around 3 asymmetrical "races" (Protoss, Terran, and Zerg) designed to vary dramatically in play styles, but retain fair and balanced game play. The mechanics of this design contrast to Starcraft's predecessor: Warcraft II: Tides of Darkness, which has two races with a nearly identical selection of units that differentiate only graphically.

General Differences
Each race derives its unique game strategy though its respective unit philosophy. As such, the player's choice of race is crucial, because each race requires a completely different playing style.

Protoss units are typically more powerful and durable, at the cost of being extremely expensive. The primary Protoss mindset is to use a smaller number of much more powerful units to tank an enemy. For example, the first available Protoss ground warrior (The "Zealot") is twice as expensive as its Terran counterpart, and four times as expensive as its Zerg counterpart, however, even 2 enemy units against one Zealot would side in favor of the Zealot.

Terran units are generally fragile, control-intensive units with specialized purposes. Terran units have been designed to be used in junction with each other, in strategic combinations and formations - often mimicking real-world warfare tactics. For example; a basic Terran combination is to take Marines (ranged gun-wielding units), use an ability called "Stim Packs" (similar to instant steroids - making units temporarily stronger at the cost of health) alongside Medics (able to constantly heal other units) to engage more enemies than otherwise would be possible.

Zerg units are cheap, and fast to produce en masse. The insect-like Zerg are designed around swarm tactics, and while no single Zerg unit could stand up easily to its counterpart, several units can overwhelm and flank an opposing unit. For example, four Zerglings (the first available Zerg foot soldier) cost the same as a single Protoss Zealot, and (depending on upgrades) could make short work of the unit.

Imbalances and Corrections
StarCraft is often praised for its well balanced units and racial abilities: no matter which race is chosen, players of equal skill have more or less equal chances to win a game, even though the races are highly dissimilar. The balance between the races has occasionally been fine-tuned by tweaking characteristics of individual types of units, such as in expense, build time, or duration of a unit's spells (special abilities that a unit may use instead of regular attacks), with the changes incorporated in a software update that is included in new CD prints and that must be downloaded to play online, along with changes made to pre-existing units in the expansion pack StarCraft: Brood War. For example; in an update subsequent to the release of Brood War, the duration of the "Disruption Web" spell (an ability that temporarily prevents ground units underneath the web from attacking air units) cast by Protoss Corsairs was substantially reduced, in response to what became perceived as the extraordinary advantage provided by the Disruption Web in the original Brood War release.

Fundamental Terran Differences

 * Terran buildings can be placed on most normal, unoccupied patches of ground. Many technological advancements, such as Nuclear Missiles, require small buildings ("add-ons") that must be built or attached to larger preexisting buildings.
 * Most large Terran buildings can lift off, allowing them to hover and fly slowly for relocation or defense against ground-based enemies. Floating disables these buildings' production capabilities and leaves behind attached add-ons (should the building land elsewhere). Large buildings that have corresponding add-ons may be built (or may land) next to an open add-on and connect to it. Similarly, any add-ons left behind by a fleeing Terran player can be captured by another Terran player by landing or constructing the required building next to it.
 * Terran units are trained one-at-a-time in specialized buildings. More advanced units typically require more advanced production buildings, or require additional buildings outside of the production building. For example; the Marine is produced from the basic Barracks building, and requires no additional buildings. The more advanced Wraith air-fighter is produced from the Starport (an advanced building you must build up to). The Battlecruiser is produced in the starport, but it requires the Science Facility with the Physics Lab add-on to be built first. Overall this means that drastically changing strategies mid-game is a very costly and time-consuming procedure.
 * Terran buildings that have sustained critical damage (depicted by hit points in red text) will catch fire and slowly burn until the building is completely destroyed or until it is repaired to at least a stable (yellow) condition.
 * While Terrans have no innate healing ability, they can build units with HP-recovering abilities. SCV units can repair Terran buildings, mechanical units, and other SCVs by moving adjacent to them (or directly below air units and hovering buildings). Multiple SCVs can work together to repair buildings and mechanical units faster. Repairing costs a portion of the player's resources. Medics, introduced in Brood War, can heal biological ground units (Marines, Firebats, Ghosts, SCVs, and fellow Medics, as well as certain allied Protoss units and all ground-based Zerg allies).
 * Excluding the SCV, all Terran units are in some way ranged attackers. In addition, Terrans possess the longest ranged ground attacker in the game (the Siege Tank), which can fire beyond its sight range.

Fundamental Zerg Differences

 * All Zerg units and buildings are biological, and will slowly recover from damage over time. Zerg buildings cannot be repaired, and units cannot be actively healed (unless through an allied Terran Medic).
 * Zerg buildings must be created by sacrificing a Drone. The Drone "mutates" into the building at the selected location.


 * All Zerg buildings other than the Hatchery and the Extractor must be built on Creep (a nutritious slime spread by Hatcheries, Creep Colonies and derived buildings). Zerg players may place buildings on enemy or ally-produced Creep, and buildings will remain if the original Creep patch recedes.
 * All Zerg units are evolved from larvae or from other Zerg units. Larva are spontaneously generated every 15 seconds by Hatcheries, up to a maximum of 3 larvae. Advanced buildings do not produce units, but rather allow new types of units to be evolved at Hatcheries. This allows the Zerg to produce many advanced units as soon as they are available. For example, once a player has finished their Spire, they can quickly make a large group of mutalisks. Once they have a Greater Spire, all of those Mutalisks can be morphed to Guardians or Devourers. This is all assuming that the player can afford it.
 * Similar to units, buildings are evolved either from Drones or lesser buildings. More evolved buildings give you more advanced unit options, even more advanced buildings, or may just act as defensive structures. For example, the Hatchery can be upgraded to the Lair and the Hive to enable production of advanced units and buildings. Creep Colonies can also be upgraded to Spore Colonies (anti-air defense) and Sunken Colonies (defense against ground units).
 * Zerg units generally use fewer "Supply Points" (points that determine the maximum size of your army) than the other races, and there are two units that use less than one supply point. For example, Zerglings take half a supply point each. Protoss Zealots, on the other hand, take 2 supply points each, allowing a Zerg player to have 4 Zerglings for every 1 zealot.
 * Most Zerg ground units can gain the ability to burrow, allowing them to hide indefinitely unless detected.
 * Zerg Supply Points are provided by Overlords, flying units that can also be used as transports and detectors.
 * The Zerg is the only race capable of producing kamikaze units: the Scourge, a cheap flying unit, and the Infested Terran, created by a Zerg Queen after using "Infest" on a Terran Command Center.

Fundamental Protoss Differences

 * All Protoss units and buildings have shields that absorb damage and slowly regenerate, somewhat faster than Zerg health points. When a shield is depleted, the unit or building takes permanent damage that cannot be repaired, although its shield will still regenerate over time. Unit shields can be instantly replenished at a Shield Battery. Biological units such as the Zealot can be healed by an allied Terran Medic, but mechanical units such as the Reaver cannot be repaired by allied Terran SCVs.
 * Protoss buildings must be built in the vicinity of Pylons, buildings that also produce the Psi that is used for Protoss supply count. Protoss buildings whose power (Psi) supply is cut off due to destruction of the Pylons powering them stop functioning but remain undamaged. Exceptions are the Nexus, Pylon, and Assimilator, which are self-powered.
 * Protoss buildings are warped in, as opposed to being built, so a single Probe (The protoss construction unit) can continue working directly after a building is begun.
 * Protoss units are trained in the "standard" manner, where a single production building will produce one unit at a time from a given selection. More advanced units typically require more advanced production buildings, and many require additional buildings outside of the production building. For example, the Zealot is produced in a Gateway, and requires no additional buildings. The more advanced Shuttle is produced from the Robotics Facility, which is an advanced building that must be built up to. The Reaver is built in the Robotics facility as well, but additionally requires another building called the Robotics Support Bay.

Resources
Like most real-time strategy games, the game is centered around resources. Resources are needed to construct units and buildings and more advanced units require more resources. In order to win, players need to balance between quickly expanding to resource locations to gather as many resources as possible, defending those locations against the enemy, and preventing the enemy from gathering them for themselves. StarCraft features two kinds of resources: minerals (required for all units) and Vespene gas (required for upgrades and more advanced units). Minerals appear as blue crystalline formations protruding from the ground and are 'harvested' by worker units (drones, SCVs, or probes, depending on the race) while Vespene gas appear as green clouds forming above geysers. Vespene gas, unlike mineral crystals, can only be harvested after a refinery building is constructed over the geyser.

As in many other RTS games, players cannot create an arbitrary number of units; each unit has a "supply/support" rating that adds to a pool. Each race's main building provides a certain supply capacity at the beginning of the game. If the player is to build more units after reaching this capacity, they must build units or buildings providing additional supply to extend their supply pool (Supply Depots for Terrans, Pylons for the Protoss, and Overlords for the Zerg). The game sets a maximum supply of 200 for each player; beyond this limit the player can no longer create units even if more supply-providing units or buildings are produced. However, Protoss Dark Archons can mind-control additional units even if the supply limit is reached and can allow the creation of a mind-controlled army with its own 200 maximum supply by a mind-controlled Zerg Drone or Terran SCV creating a Hatchery or Command Center, respectively. Smaller, weaker units use as few as a half supply (2 Zerglings are spawned for 1 supply) whereas larger ones, like Battlecruisers or Carriers, can use up to six or eight, respectively. Overlords take up no supply. Supply can be seen as a third resource, because it has to be managed at least as carefully as minerals and Vespene gas, especially at the beginning of the games.

Besides using a Dark Archon, there is one exception to the 200 maximum supply. If a player chooses to play custom or multiplayer mode, the player can change the game settings to "Team Free For All". The player then chooses to make his team the same race. This gives the player 800 as a supply limit. This is not recommended when it comes to zerg or playing with more than two players, since it will probably make game lag very badly when one comes up to those numbers.

Battle gameplay
Starcraft uses distinct attack types and unit size types. This feature gives every unit a distinct characteristic beyond its attack/hitpoint ratio and makes some units much more effective against others. The unit size types are:
 * Small - Zerglings, Zealots, Marines, worker units, etc.
 * Medium - Hydralisks, Lurkers, Vultures, Corsairs, etc.
 * Large - Ultralisks, Siege Tanks, Archons, Dragoons, buildings, etc.

The attack types are:
 * Normal - full damage against all unit sizes
 * Concussive/Plasma - full damage against small targets, 50% damage versus medium and 25% damage versus large
 * Explosive - full damage against large targets, 75% damage versus medium and 50% damage versus small
 * Splash - hits units close to the detonation or blast area for a small radius, with units closer to the center of blast taking more damage--an attack can be both concussive or explosive in addition to doing splash damage.

It should also be noted that Protoss shields take full damage from all damage types, regardless of the unit.

With this system, matchups between the races constantly change over the gameplay time as different units become available.

For example, the Protoss Dragoon, a unit that uses explosive attacks, can be easily destroyed by large swarms of Zerglings because the Dragoon deals only half of its normal damage to small units, but the Zerglings' normal attacks deal their full damage to the Dragoon; also the Dragoon is a large unit, allowing the small Zerglings to swarm around the unit and destroy it with relative ease.

Starcraft is also unique in that all units are useful at all levels. Bottom tier units can be used effectively up to the end of the game. In addition, there is a counter to every unit in the game. This ensures that unit diversity is required to win. That is, simple massing of one powerful unit is bound to fail, as it could easily be defeated with the proper units. For instance, masses of Marines and Medics are a powerful force but can easily be countered by Zerg Lurkers. To counter the Lurkers, Siege Tanks and Science Vessels are used. The Zerg could then employ the Defiler's Dark Swarm technique in addition to spreading its force out to avoid direct damage as well as splash damage from the tanks. The Terran would then focus on using the Science Vessel's Irradiate ability to kill the Defilers, which would cause the Zerg to create Scourge to efficiently destroy the Science Vessels. However, the Scourge could just as easily be defeated by the Marines. This is just one example of how Starcraft can become a game of counters.

Unit movement
Starcraft units also have variable speed and maneuverability, which can be very important in determining whether a unit can strike while the enemy is unready or can allow units to retreat from an uneven battle.

Some examples:

The Protoss Zealot versus the Zerg Zergling: Four Zerglings cost the same as one Zealot, but Zerglings are much more versatile at the beginning of the game and will kill the zealot, because they move so much faster and attack faster than the Zealot. Later in the game, however, the Zealots can have their speed upgraded to a level equal to that of the Zergling. This makes the Zealot useful both at the beginning of the game, where it is the first combat unit the Protoss can construct, and also at the end of the game, where it becomes the fastest Protoss ground unit. The Terran Siege Tank: With the proper upgrade, it can turn itself into a static defense unit, similar to the "mobile artillery" units of other games. This mode, called "siege mode," increases its range and attack power by about 100% but forces it to remain stationary. Switching between modes takes about 2 seconds, so a Terran player usually moves his tank force in small groups, teamed up with vultures, with one group in siege mode providing cover fire for the group advancing on the enemy. This is strategy is called 'tank-push' (or terran push).

Starcraft also features aerial units that can travel freely over the map without having to travel through choke points to get to enemy bases. A common strategy is to take six to twelve mutalisks and kill undefended workers before reinforcements arrive. Furthermore, these air units have no collision, thus air units can be stacked on top of each other taking up very little space. This allows skilled players to maneuver large airborne armies around anti-air defenses and strike vulnerable areas. Their drawbacks are that they are more expensive and require the player to have built more specialized buildings before they can be constructed than ground units. Generally, they are also somewhat weaker and can be countered by specialized units and buildings, such as the Corsair (Brood War only), Valkyrie (Brood War only), Devourer (Brood War only), Scourge, Missile Turret, Photon Cannon, and Spore Colony.

Unit sight range, visibility, and detection
Players are only able to observe the map areas in proximity to their units and buildings (there are a few exceptions, including parasites, allied vision, and Comsat Stations' scanner sweep). Unexplored landscape shows as complete darkness to the player. Previously explored landscape is "remembered" but covered in the so called fog of war where enemy units may exist unseen. Most units see slightly farther than they can shoot, but there are exceptions (e.g. Terran Siege Tank in siege mode).

Some units are invisible or can become untargetable in certain states. Such units can only be targeted if the enemy player has a detector unit or building present, or if a special ability is invoked. There are many ways to counter cloaked units without detectors, but these may be very hard or risky to execute. Such examples include having a Siege Tank in siege mode attack near a cloaked ground unit, causing the cloaked unit to take splash damage or attacking one of one's units with a Reaver that is near cloaked units and putting the unit inside a shuttle before the scarab hits the units.


 * Protoss Detectors include the Observer, which is also permanently invisible, and the Photon Cannon building.
 * Zerg Detectors include the Overlord and the Spore Colony building.
 * Terran Detectors include the Science Vessel, the Missile Turret building, and the Comsat Station (add-on to the Command Center); the Comsat Station is unique among detectors in that, rather than providing permanent detection in its range of sight, it provides a temporary detection of any arbitrary spot on the map selected by the user but requires energy to do this that can run out and must be replenished. Spider mines are not detectors, but they can attack cloaked units.

Though both units and buildings may be detectors, no building is ever untargetable. Units that can become untargetable are the following:


 * Protoss Cloaking Units include the Observer and Dark Templar, which are both permanently cloaked. The Arbiter also cloaks all friendly units near it continuously, except for other arbiters.
 * Zerg Burrowing Units include Drones, Zerglings, Hydralisks, Lurkers, and Defilers. These Zerg are capable of burrowing themselves to become invisible (though immobile) indefinitely in any terrain.  Drones, Zerglings, and Hydralisks become unable to attack in this state, while Lurkers can only attack while burrowed. Defilers are often burrowed while regaining their energy.
 * Terran Cloaking Units include the Ghost and Wraith, which both consume energy in order to remain cloaked for a limited time. Spider Mines burrow similarly to the Zerg to stay invisible indefinitely. These mines can detect cloaked units and attack them, although the owner of the mines cannot see the cloaked units themselves.

Units frozen under a stasis field cannot be attacked, moved, loaded, or teleported.

"Cloaked" units feature a visual effect of distorting the images of the ground beneath them, most noticeable when the units move, which limits their invisibility to enemy players. But unlike the game's predecessor, Warcraft II, units cannot be commanded to "Attack Ground" in order to manually hit units without targeting them. Untargetable units can still be damaged or destroyed as a result of "splash damage" or "area-effect" spells.

Ground-level note: Units at the bottom of a cliff cannot see anything on the top of the cliff. If the player with units below uses an aerial unit to reveal enemy units on the high ground, however, the ground units on the bottom can also attack targets on the top (with 70% accuracy). There is an exception to this, which is when the units on the top attack the bottom level: the units can be seen for a while, enabling counter-attack (again with 70% accuracy).

Special-ability notes: Detector units lose their detection abilities when they are Blind (affected by the Terran Medic's "Optical Flare" ability in Brood War). Invisible units can sometimes be forcefully de-cloaked by invoking EMP Shockwave or Feedback (on energy-consuming cloakers only) or by casting the area-effect spells Ensnare, Plague, or Stasis Field or by a Devourer's Acid Spores. Many spells leaving effects on units will keep them continuously visible to every player (e.g. Maelstrom, Lockdown, Defensive Matrix, Acid Spores, Irradiate); these abilities do not require the unit to be visible while the spell is cast. However, the Zerg Parasite only enables vision to the caster of the spell. Zerg Parasites not only can keep otherwise invisible units visible but also can make enemy detectors relay their detection to the player. The ComSat Station's satellite scan reveals an area of the map, including cloaked units.

Single-player game
There are two modes of play for solitary players: a series of single-player missions, divided into three episodes (one for each race, plus three more episodes in StarCraft: Brood War) and the possibility to play custom games either allied with or against up to 7 computer-controlled opponents.

The single player missions serve the double purpose of telling the game's story and introducing players to the units and specificities of each race. These missions mostly require the player to destroy several different enemy bases; sometimes additional objectives like protecting certain "heroes" (special units) or destroying specific buildings (such as a Confederate Ion Cannon in the last Terran mission of StarCraft), bringing units to a specified position, or defending a base against incoming assaults for a given period of time. Since they are also intended to gradually introduce the units unique to each race, many missions place restrictions on the units and technology the player has at his/her disposal for the duration of the mission. For example, in the first missions of StarCraft, the player cannot build advanced units like Battlecruisers or "research" powerful upgrades like the Siege Tank's siege mode (which enables Terran Siege Tanks to do more damage). Usually, the player already has a more or less established base and a number of combat units at the beginning of the single-player missions.

Custom games in the Melee mode (the mode most often used) against computer opponents are very similar to online games against other human players, with the exception that computer controlled players often display very characteristic behaviors (like the ability to give several orders simultaneously, or distinctive building and expansion patterns). Both the players and any computer players (up to 7 can be set up) start with only a main building (the building used to produce workers) and four workers, regardless of the race selected. No combat units are provided at the beginning. Players, human and computer-controlled, must then set up a base as quickly as possible and start producing combat units in order to overpower enemy forces. The game is won when all enemy buildings are destroyed (this opens up the possibility of crippling an enemy by destroying all units, but not the buildings.)

Multiplayer game
StarCraft users can play against other players via a LAN or the Internet, using Blizzard's free Battle.net gaming network. The most popular game type is a 1 vs. 1 duel played in Melee mode. This game type is won by destroying all of the opponent's buildings. There is a game type called "One on One." but for most players don't use it, because it takes time to switch between types, whereas "Melee" can do free for all and 1 on 1 death matches as well as more than 2 team games. However, other, less commonly played game types also exist. From StarCraft.org:
 * Types of multiplayer gameplay include:


 * One on One (Deathmatches)
 * Team (Two or more players controlling a single team civilization)
 * Melee (Free For All or Separate Player Team Play)
 * Capture the Flag (Capture all the enemy flags to win)
 * Sudden Death (Destroy any enemy town hall, [Command Center, Nexus, Hatchery/Lair/Hive] built or existing for instant win)
 * Slaughter (Race to see who can get the most kills in an allotted time [buildings and units])
 * Greed (Race to an allotted amount of minerals and gas, eg 5,000 minerals and gas)
 * Ladder (Ladder matches to determine World Wide Ranking)

A One on One duel with reasonably experienced players (played at highest game speed), typically lasts between 8 and 30 minutes, the average being about 15 minutes. Traditionally the game does not end with the utter annihilation of one party. Instead, the losing player, when he does not see any chance of winning, sends the message "gg" (good game) and leaves the game, resulting in an automatic victory for their opponent.

There is a limited amount of resources at each location, and only a limited amount of resources can be gathered in a specific time frame from one location. Depending on what race the players choose, one player might need to expand to considerably more resource locations in order to win the game.

Measuring mastery
Many StarCraft players recognize three skills essential to becoming a good player: micro-management, macro-management and multi-tasking.
 * Micromanagement refers to unit control, especially in battle. Having this skill means to attack only when it's cost-effective, retreat fast enough in case you see it's not (effectively doing more damage with fewer units), while preventing the enemy from doing the same. Combat maneuvers such as flanking, concentration of force, and luring enemy units into a trap fall under this category of skill. It requires knowledge of the units, their shooting range, speed, abilities, strengths and weaknesses, as well as some knowledge of the terrain and map.
 * Macromanagement means to keep your economy running, expanding at the right moments to the best locations, picking the right upgrades, building towards and producing the right units in time, spying on the enemy, predicting his moves and, hopefully, outsmarting him. It requires knowledge about the tech-trees (for prerequisites), the map (where to defend, where to attack, where to expand) and potent unit-combinations (which units are most effective against enemy unit combinations).
 * Multitasking refers to being able to do many things at the same time. StarCraft enables the player to use a variety of shortcuts to jump to a specific position on the map and give fast orders. Having this skill means, for example, to defend and attack at the same time, while not neglecting your micro-management and still working efficiently towards your long-term goals. If the opponent is confident, he might try to distract you with something, usually surprise unit drops, for you to take care of in order to 'steal your time'.

Sometimes Actions Per Minute (or APM) is used as a quantitative indicator of one's ability to micro- and macromanage. A player's APM rating is determined by calculating the average number of actions that a player performs during each minute beyond the first 80 seconds of a game. An action in StarCraft is defined as selecting a unit/building or giving an order to a unit/building. The way you select the action does not matter, i,e. selecting attack and left clicking on a target is the same as right clicking it, since it is the default action, it is just 1 action (the orders are recorded complimentary with their intended target, if one is required, so it counts just as one action, so if you select an order and cancel it nothing will be recorded in the replay file); creating a building does not count as 3 actions, but just 1, although you have to select the appropriate sub menu for basic or advanced buildings, select the building needed, and designate the building location.

Having a high APM rating does not necessarily mean that one is a skilled, or even decent player; but a high APM rating usually indicates a fast, active player. In other words, though a high APM does not guarantee success, a very good player almost always has a high APM. Professional gamers (such as those in South Korea) have been known to achieve average APM ratings of over 300, and peak APM ratings, such as during a battle, of over 600 and sometimes, although during a splitsecond their APM can rise higher than 1000. Even the "slowest" progamers have an average of 250 APM during a game (more than 4 actions per second). The computer program BWChart allows StarCraft players to determine their APM rating for a recorded game.

A typical multiplayer game
Even though new tricks and tactics are still being discovered despite the game's age, it is possible to outline what usually happens in a "one-on-one" between experienced players.

The map and thus the resource locations are known to both players. However, many multiplayer maps have several possible start locations. In a Melee game, each of the players is randomly placed on the map at one of the possible spawn points, unaware of their opponent's position. Everything out of the sight radius of their units appears black, any buildings or terrain that has been seen at least once by a player's units will be shown grayed out in the last known status — this effect simulates fog of war. Each player starts with four resource-collecting units (SCVs/Drones/Probes) and the structure needed to build more workers (Command Center/Hatchery/Nexus), near a resource location.

General theory
Generally, Starcraft strategy depends on effective spending. There are three areas to focus one's spending: unit quantity, technology, and economic strength. Skilled Starcraft players generally have a keen grasp of when to invest in each, depending on their race and the opponent's. For example, in the early game, a Protoss player may construct two Gateways relatively quickly in an attempt to seize the quantitative advantage. He could also construct a quick Forge instead in an attempt to 'tech', or possibly expand rapidly with some combat units for defense, in order to gain the economic advantage.

In each case it is important for the opponent to make an educated decision on what to do depending on their races. For example, it is difficult for a Terran to defeat a teching (focusing on technological development) Protoss through sheer quantity of first-tier units - if the Terran cannot win with his superior numbers of marines and medics by the time the Protoss technology kicks in, his troops will quickly die to reavers, psionic storms, or a good number of speed-upgraded zealots/well micromanaged range-upgraded Dragoons (depending on what the Protoss researched). The Terran will not have an advantage in any of the three areas. Therefore, the Terran's best bet is to upgrade technology as well. If the Terran, however, sees the Protoss expanding quickly, they may be better off upgrading technology initially (perhaps dropping tanks on a cliff overlooking the Protoss expansion base, in an attempt to nullify the economic advantage).

In another sense, however, unit quantity matters less and less as numbers increase. When both sides only have 2 dragoons, it is unwise to spend minerals expanding because the extra 3 dragoons that could have been trained will be sorely missed in a battle against a numerically superior foe. However, if both sides have 24 dragoons, the value of additional troops is severely diminished, and the minerals are better spent increasing one's advantage in another area.

Furthermore, battles are a key factor in the gameplay. After winning a decisive battle, it is generally unwise for the victor to immediately try to finish off the opponent, because they are most likely concentrating all their resources on constructing troops to match the victor's army, or constructing a powerful defense around their main base. Instead, it is more important to expand, while making sure that the opponent doesn't. Although the loser of the battle may end up with a slight troop numerical advantage, the victor's economic strength is so great that the loser cannot possibly hope to match the massively increased flow of units. This is why many players frequently exit before all their buildings are destroyed - they realize after losing several critical battles they can no longer maintain map control and can do nothing to prevent the victor from securing a massive economic advantage, to be converted into superior troop quality and quantity.

Early game
Both players start collecting resources immediately after the game has started. Zerg players, controlling the only race starting with a movable unit not usable or required for resource gathering, will often use their Overlord to scout (look for the enemy) right from the start. Other players will wait a minute or two before sending one of their workers to scout, so as not to lose any resource collection capacity during the crucial beginning phase. Scouting to keep informed about incoming threats and weaknesses of the opponent's strategy is a vital part of the game. Throughout the game, players position cheap and/or cloaked units (ie. burrowed Zerglings), or fast-moving units at strategically important positions in the map.

As players start scouting, they also start building the structures needed to accomplish their first goals. A player can prepare for an early attack ("rush"), fortify his base against such attacks, focus on building his "tech-tree" to have advanced units earlier in the game, or expand his base in order to outmass the enemy in the long-term. Each strategy has its strengths and weaknesses. Temporary advantages can be gained at the cost of longterm disadvantages and the other way around. This creates a pressure to be informed about the enemy's movements and use the edge while it exists.

If the player chooses to attack early, then he will start doing so after 4 or 5 minutes. There are several known tactics for early attacks and how to best protect oneself against them. When two "gosu" (skilled players) play against each other, early attacks can be as dangerous for the attacker as they are for the defender. Indeed, a large economic commitment must be made in order to have any hopes of succeeding in defeating the opponent in an early attack, and the attacker must neglect other parts of his economy. This decision can later put him in a difficult position, should the "rush" fail. Very short games usually are the result of a successful or unsuccessful rush.

Expansion and struggle for resources
If both players survive the first 10 minutes, they start the battle for space. The players will try to get and hold as many resource locations as possible as well as prevent their opponent from doing so. The players start this quest with the handicap or the advantage they acquired during the early game. During this part of the game, the players will stock up their army and try to weaken their enemy by various attacks on resource locations, tech-buildings (structures required to research upgrades and build advanced units), as well as production facilities.

Different races typically require different amounts of map control. Zerg, for example, is usually played to dominate the map quickly, due to their cheaper expansion bases, whereas a good Terran player can often get by on one mid-game expansion and just deny the enemy from getting more expansions of his own. The battle for map-control often depends on the racial matchups.

During the rest of the game both players will try to obtain resource domination. A considerable resource control advantage can still be broken by finding weaknesses in the opponent's strategy, a come-back. A simple example of this is to build a lot of air units, when the opponent has little anti-air defense, because they had built units for large-scale ground combat. Another common example is using a transport to drop units in the center or back of the opponent's base, far from the frontal defenses and units. Sooner or later one player will start dominating the game, winning more and more ground. Because small advantages tend to increase over time and players will prevent each other from harvesting, the total length of a game is rarely limited by the amount of resources, but rather the amount of resource locations on the map. Long games are rare.

Ending
In a typical ending the stronger player sends a massive amount of combat units towards the other player's main base. The losing player tries to delay the attacker in order to collect his troops for defense. The attacker will push the defender to the outskirts of the base, still with enough troops to defeat the enemy on his own ground. The defender, having almost no troops left and the opponent's army at the outskirts of his main base, surrenders. However, players often surrender before a massive attack happens, because they realize they won't be able to get a resource advantage anymore.

Games also come to an end if one player can force another into a position where they can no longer function. One example is when a player destroys all of the enemy's workers at a time that the enemy has less than 50 minerals (the cost of one worker). Another example is destroying all of an enemy's main buildings (Command Center, Nexus, Hatchery/Lair/Hive) at a time that they have fewer than 400 minerals (300 for a Hatchery), the cost of one of these structures. Both of these scenarios effectively cripple a player's economic ability. However, it is generally a fluke to have this happen, so it should not be intentionally played for.

Longer, drawn out games usually end in a battle for the last resource location on the map, where the attacker desperately launches an offensive with his last forces to capture the location, while the player currently controlling it, fortifies it, by whatever means possible.

Matchups
These descriptions are meant as a general guide to human competition. Actual games, especially at lower levels, often involve 'cheese' strategies, such as dark templar rushes, placing tanks on cliffs, rushing with cannons/bunkers/sunken colonies. Map structure and player skill play far larger roles in determining imbalances between races than the races themselves, so statistical analyses are typically skewed by which maps were most popular at the time. Most maps tend to follow a T > Z > P > T pattern.


 * Terran v Terran - The slowest matchup, this mirror matchup frequently depends on effective drops, macromanagement, and controlling the map. Most high-level games revolve around mechanical units from the factory or starport, like the tank, goliath, wraith, battlecruiser, and dropship.


 * Terran v Protoss - This matchup generally centers around the ability of the Terran player to 'push' across the map with vultures, siege tanks, and missile turrets. The Protoss player normally counters with zealots and dragoons, occasionally mixed in with some spellcaster/dark templar support.  Late game frequently sees the Terran player shifting to goliaths instead of vultures as the Protoss player shifts to air units like the arbiter or carrier.


 * Terran v Zerg - On the Terran side of this micro-intensive matchup, the units almost always start off as a mix of marines, medics, and possibly firebats, later mixed in with tanks and science vessels. The Zerg player may counter with either mutalisks, transitioning into guardians, or lurkers, or occasionally mass hydralisks.  Late game, however, most experienced Zerg players begin production of defilers for the Dark Swarm spell while attacking with a mixture of ultralisks, hydralisks, zerglings, and/or lurkers.
 * Protoss v Protoss - This mirror matchup is heavily dependent on macromanagement. Early game may see a zealot production race, but more often than not, midgame transitions into dragoons mixed with either reavers or templar, with much of the game revolving around effective drops.  Lategame frequently sees a shift into production of zealots, archons, and high templar instead, or occasionally arbiters and/or carriers.


 * Protoss v Zerg - A very demanding matchup for the Protoss player, as at the pro-level Zerg fares noticeably better. The Protoss player's unit force is heavily dependent on what the Zerg player produces. Generally, the Protoss starts with zealot production and from then on counters lurkers with dragoons and observers, zerglings with archons/zealots, and mutalisks with archons/corsairs.  The key units in most games for the Protoss are the templar: the high templar's Psionic Storm spell is effective at dealing with large masses of troops, and 2 high templar are needed to create an archon; while the permanently cloaked dark templar can either serve as an attack unit or be used to create dark archons that offer a variety of spells.  The Zerg side usually sees either mutalisks, hydralisks, or lurkers midgame, and a late-game transition into ultralisks and zerglings, occasionally under cover of Dark Swarm.  In addition, because of how easy it is for Zerg to change their unit strategy, Zerg often attempts to force the Protoss into a passive position, thereby allowing the Zerg player to out-expand the Protoss and win through sheer volume of troops.


 * Zerg v Zerg - Of all matchups, this is seen as the most volatile and an exception to the general rule that one should always produce workers. Due to the nature of Zerg's unit production, constructing too many workers uses up larvae and results in a depleted army.  This matchup is almost always fought with an early game zergling battle, traditionally transitioning into mutalisks and zerglings, often with scourge support.  Occasionally the midgame sees hydralisks with queens, but lategame usually transitions into mutalisks, devourers, zerglings, and defilers.