Psi

Psi is a protoss gameplay counter limiting the number of protoss units. The counter (available psi) is increased by constructing pylons and the maximum is 200. New units may be produced so long as the cumulative psi "cost" of all active units does not exceed the available psi.

Terran supply and zerg control serve the same purpose.

In strategy discussions, psi levels may be denoted as x/y, where x is the psi used, and y is the total available psi.

StarCraft

The 200 point limit may be exceeded through the dark archon's mind control ability; this is legal and no new units may be built until consumption falls back below 200. The counters for supply, psi, and control are kept separately; a 600 point force may be constructed by capturing SCVs and drones and building up the non-protoss tech trees.

Producers

	Building/Unit
9	Nexus
8	Pylon

Consumers

	Units
1	Probe Observer
2	Zealot Dragoon High templar Dark templar Shuttle Corsair
3	Scout
4	Reaver Archon Dark archon Arbiter
6	Carrier

StarCraft II

Producers

	Building/Unit
11	Nexus (LotV)
10	Nexus (WoL/HotS)
8	Pylon

Consumers

	Units
1	Probe Observer
2	Zealot Stalker High templar Dark templar Warp prism Sentry Phoenix Mothership core Adept Zealot Ascendant Avenger Blood hunter Centurion Corsair Dragoon Energizer Havoc Mirage Sentinel
3	Void ray (Wings of Liberty) Oracle Disruptor
4	Immortal Archon Void ray (Heart of the Swarm) Annihilator Arbiter Dark archon Destroyer Vanguard
6	Carrier Colossus Reaver Tempest (Legacy of the Void campaign and multiplayer) Wrathwalker
8	Mothership