Psi

In StarCraft, each Protoss player has two Psi counters - the first refers to the amount of psi being consumed by the player's units and the second refers to the amount of total psi available. The difference in the two numbers is the amount of psi that is still available for constructing additional units. Once the difference in the two numbers reaches zero, a player will not be able to construct any additional units. Hidden is a 200 point psi max, the limit beyond which your production structures can no longer turn out units no matter how many psi production objects you create.

Here is a list of how much Psi each unit takes:

1 Psi: Probe, Observer

2 Psi: Zealot, Dragoon, High Templar, Dark Templar, Shuttle, Corsair

3 Psi: Scout

4 Psi: Reaver, Archon, Dark Archon, Arbiter

6 Psi: Carrier

A Pylon provides 8 control, Nexuses offers 10 control.