2 Gate Robo
From Liquipedia Starcraft 2 Wiki
The PvP 2-Gate Robo is an ultra-safe build designed to directly counter the standard 4 Warpgate Rush, the build focuses on getting a very early Immortal while defending against early Zealot and Stalker pressure. The build cleanly transitions in to the midgame, setting you up to get a quick observer to judge whether or not expanding or being aggressive is the correct path.
The goal of the build is to defend the player from the all too common 4 Warpgate Rush while setting you up for the midgame. The build get's out two early Sentries, an Immortal, a Zealot and a Stalker for exactly the 5:45 mark, to defend against the first push of the 4gate. When the player sees that he/she are safe, they can get out an Observer and assess whether or not to expand, attack or tech further. The pros of the build are that it provides safety against the most common of Protoss builds, and provides you with the means of playing in a reactionary style for the midgame. The con of the build is that it requires absolutely perfect timing to get the right amount of units to hold off the push.
 Basic Build Order
- The timings of the Chronoboosts are imperative to the build as a whole, every timing needs to be hit to ensure that all units will be out in time to defend against pushes.
- Important to keep first Stalker on Xel'Naga tower to spot incoming aggression.
When scouting during this build, look for the usual PvP signs. If your opponent is going Forge first, begin scouting and get ready to defend against a cannon rush. If the player is saving up Chronoboost he is almost certainly going 4Warpgate, in this case continue build as usual. If the opponent has immediately put down two Gateways, put down a second Gateway of your own and begin to Chrono Zealots. If you scout a fast second gas and see a very low Sentry count at the ramp, this could indicate a Dark Templar Rush or quick Stargate tech, make primarily Stalkers (for stargate units) and get an observer from the Robo Bay (in the case of Dark Templar). If blink is scouted, continue build as normal, but get an in-base Observer to prevent blinks up in to your base.
In an ideal situation, the opponent will have done a 4 Warpgate Rush, at this point you can either continue scouting and tech appropriately while expanding or build a force and be aggressive. The quick Robo Tech will put you in a position to get much earlier Colossus than your opponent and follow up with a strong 1-base Colossi push. If you have this in mind, stay on 2-gate and a single Robo while hitting every warp cycle. The build leaves the player with many options, even if the opponent did not go for a Warpgate rush, there is access to an early observer and that reactionary period of time. If the opponent is falling back and defending in fear, capitalize on that and expand immediately. Scout actively and check for aggression. If the opponent tries to all-in, halt Probe production again and add another Gateway.
Take an expansion the second you feel you are safe, and if faced with serious aggression add an additional Gateway. In the case of Dark Templar, get a fast Observer. In the case of Blink tech, get an in-base Observer and resume Immortal production, snipe any observers that he tries to put over your base to prevent blink. If he techs to Charge, start making a lot of Sentries. If he you scout Robo tech, you can engage in the ever popular Colossi Wars or if it looks like you have time drop a Twilight Council and tech towards mass Chargelots and Archons while harassing with Warp Prism. If Stargate tech is scouted, make predominately Stalkers while continuing with Robotics tech tree.