3 Gate Robo Timing Attack (vs. Zerg)
A 3 Gateway Robotics timing attack is a flexible strategy that aims to punish a Zerg teching off two bases before they start producing Lair tech units.
This build culminates in a 1 base attack on a Zerg while they are saving up resources and Larva to spend on Mutalisks or Hydralisks. By getting a quick Robotics Bay and Observer, the Protoss player can adjust his unit composition according to the Zerg as he macros up while being safe from a mass Roach or Zergling opener. When the Zerg Spire or Hydralisk Den is created, the Protoss player moves out and attempts to snipe the tech building or natural with 1 or more Immortals, 2 or more Sentries, and a mass of Zealots.
 Basic Build Order
- The strength of this build is that you can keep tabs on all the Zerg tech and unit composition with your Observer, and have enough Gateways to support a push to counter said units. The main concern is whether to build Zealots or additional Immortals. A brief rule of thumb is 1 Immortal for every 4-5 Roaches or 3 Spine Crawlers. 3 Sentries will give you adequate force field. If your opponent is skipping Roaches or doing a Roach Feint you do not want to make a single Immortal more than necessary as they are quite poor vs Zerglings. If your opponent is going almost solely Roaches, you will want to have more Stalkers than Roaches.
- After the first two Chrono Boosts on your Nexus, the rest should be saved for unit production, especially for Sentries and Robotics production.
- As you move out, leave behind one Sentry at the choke to your main ready to block your ramp in case of a Zergling counter.
- Bring a Probe along with your push to drop a Pylon near the Zerg natural so you can continue warping in reinforcements.
Sacrificing Probes to scout is not as necessary because of fast Observer; however, if you see very early Roaches you may build the first Immortal before the Observer.
The build relies heavily on good micromanagement. Because Immortals are slow and easily surrounded by Zerglings, they must be kept close to your Zealot line and kept focus firing on Roaches, structures, and Queens. Good use of Force Field to funnel Zerglings, block off the enemy ramp, to prevent drones from escaping, and stopping Zerg reinforcements is critical. Picking off their Spire / Hydralisk Den with the Immortal(s) is the highest priority.
How to proceed after the initial attack is dependent on how much damage you did and what tech your opponent is attempting. If you failed to snipe their tech or their natural, or failed to kill a significant number of drones and Queens, then you are at a great disadvantage as you will be stuck on one base. If you did deal significant damage, you have the option of either expanding or get additional tech to finish them off 1 base. If they went Spire, you should add a Stargate and begin Phoenix production to complement your Zealots. If they went Hydralisks, add a Robotics Bay and switch to Colossus.
 Pro features
Short ground distance to your opponents base, such as the 9-12 and 3-6 positions on Lost Temple.
 Con features
Long ground distance and alternate paths to one's main, such as Desert Oasis.
- ForceSC2strategy - ForceSC2strategy explains the 3 Gate Robo against a Zerg.