The number of bases with working resources is one of the decisive factors for the game's outcome. In several of the Starcraft match-ups, base count is the active goal of the game. The match-ups that emphasize base count the most are Terran vs Protoss and Terran vs Terran. For any Zerg match-ups, the number of geysers a Zerg controls, a sub category of base count, is often used as the indicator of the game situation. Overall, base count and expansion timing is one of the key factors in any Starcraft game.
Terran vs Protoss
The Terran versus Protoss is often considered one of the more mechanical match-ups in Starcraft. There is an intricate balance between the tech level and the base count in these games. In standard play, the Protoss usually sticks to a two unit mix, Zealots and Dragoons. Because a Terran army made up of factory units, vultures and tanks, has superior firepower over these basic Protoss infantry units, the mid-game is often considered close or even if the Protoss controls one base (usually the mineral only) over the Terran. In this style of play, it is up to the Terran to harass and apply pressure on the Protoss so that he does not have more working bases than the Terran. Therefore, each expansion the Terran takes will force the Protoss to react, to either attack or expand again. If the Protoss mounts an assault and fails, the Terran can push out after taking advantage of the new expansion. If the Protoss expands, the Terran still gains an advantage in that the Protoss will have another base that he will be forced to protect.
One of the standard builds for this matchup is known as the one factory expand. This build tries to give the Terran an early advantage and allows the Terran to concentrate on building units for the mid-game, where most of the action in this match-up occurs. The Terran player should build a factory and get tanks and Siege Mode Research from the factory add-on right away. Meanwhile, he should be constructing his command center, usually behind his walled in base before floating it over to his natural expansion. This build works well on maps such as Lost Temple where the cliff of your main base reaches the entrance of your natural expansion. One of the newer techniques for the Terran fast expansion is the Midas Rush or its variants. Because the standard reaction for the Protoss against the one factory expand is to expand twice, the Terran usually gains no real advantage. The Midas rush aims to put early pressure on the Protoss and prevent him from over-expanding. The Terran player will usually still only build one factory, but this time collect a number of marines. Instead of the Siege Mode research, the Terran will usually research spider mine. When the first tank is produced, the small force of marines and the lone tank will push out towards the Protoss base. Meanwhile, the factory with the rally point set to the Protoss base will be constructing vultures. As the small Terran force pushes attacks, the Protoss should only have a few Dragoons and should be forced to retreat back up its ramp. This allows the vultures that follow up to lay mines at the opponent's natural expansion area and entrance of his base. This will briefly contain the Protoss, and help prevent a dark templar harass. The Terran should proceed to build a command center right away.
Terran vs Zerg
Terran vs Terran
Protoss vs Terran
From the Protoss' point of view, this match up requires them to either have an advantage in tech (templars, arbiters, etc...), or in the number of bases controlled. Because of the mobility of the Protoss army in comparison with the Terran, the Protoss can usually expand around the map while having its main army hold the middle of the map. A Protoss player of this match-up should always keep track of the number of working bases on either side. This is a good indicator of the situation. Because of the high number of bases, the Protoss is forced to protect them all from Terran harass which will include vultures and dropships. If the Protoss successfully holds its base count advantage, the Protoss should reach a point where its army is large enough to mount an assault on the Terran. In longer games, a base advantage will also allow the Protoss to start constructing Carriers against a well ground fortified Terran. The standard play of this match-up calls for the Protoss to create fast observers. This allows the Protoss to see what form of harass the Terran will open with, or if he is going to expand early. The Protoss should then be able to successfully defend the harass and expand ahead of the Terran. This build is considered the safest build, since the Protoss will be prepared for whatever the Terran comes with.
A strategy that has become extremely popular recently, much like the Terran rush, is to harass before expanding. This will probably involve a two gateway build and dark templars. The early dragoon pressure will force the Terran to defend its wall and make it hard for him to early expand. The higher number of dragoons that results from this build will also make it safer against Terran rushes. If the Dark Templars do not catch the Terran off guard within his base, they will be able to protect the Protoss' early expansion as well as hinder the Terran's own expansion. Dark Templars are a key to this build because it neutralizes any Terran attempt of an early push or attack.