In the past, Protoss players used to say that when in doubt, you should just use 4-gate. However, due to the all-in nature of the 4-gate opening, Protoss players have then opted for a safer 3-gate opening which balances economy with early unit count. This allowed for various transitions, including one to Robotics Facility for Immortals, which are solid in almost any matchup. Due to its reliability, the 3-gate robo has then become a standard opening for Protoss players everywhere.
This is a standard Protoss build order that has proven quite useful in all three matchups, letting the player defend against early pressure in close positions while still allowing him to tech up and then expand once the enemy attack has been thwarted. It does quite well against mass unit openings from the opponent, especially if Immortals prove to be a hard counter against armored units in early engagements.
The goal of this build order is to be able to tech up safely while having the option to churn out units when needed. It’s also a good way to get Colossi fast while not being caught unprepared. You may also get Immortals when up against armored units. If up against anti-air, Colossi can be delayed in favor of more Stalkers. This build order can be seen as a solid way to play a standard game as Protoss, and can be a variation of your 3-gate openings.
9 – Pylon (1)
13 – Gateway (1)
15 – Assimilator
16 – Pylon (2)
18 – Cybernetics Core
19 – Zealot
22 – Pylon (3)
23 – Stalker
25 – Research Warpgate Tech
25 – Assimilator (2)
26 – Gateway (2)
27 – Sentry
30 – Pylon (4)
30 – Gateway (3)
31 – Robotics Facility
This strategy is great for maps with narrow choke points where you can use Force Fields to split enemy armies up. It’s also good with the Colossus’ Thermal Lance in that it will kill of bunched-up units quickly. Most map features that favor the 3-Gate Robo tend to be centered around the Colossus due to its unique features, one of which can be taken advantage of with multiple elevations like that in Shakuras Plateau. You can micro Colossi to high ground and back in order to hit hard and not get hit.
This isn’t as good in maps where there are wide open spaces. Units with high DPS like Terran Marines can easily get surrounds or concaves around your units and kill you off quite easily in such maps. You also wouldn’t want to do this in maps with fairly large air spaces where air units can thrive and harass the hell out of you until you just GG out of absolute frustration.
Check if your opponent is mining gas to determine their approach in that game. Not mining gas at the usual time may mean that he’s going for a rush with mineral units like Zerglings or Marines. If you do see a rush coming, cut probes and don’t build the Robotics Facility yet and deal with the threat accordingly. Sentries are great in resolving such situations, but they do cost quite a bit of gas. You may build a Forge if necessary and put up Photon Cannons for additional defense.
You should usually scout with your 9-Pylon Probe to scout out cheeses. You can also make sure that you can actually get into the Terran base before it gets completely walled off. You must then keep the Probe alive as long as possible in order to see whatever he’s doing. Remember that if he’s too afraid of having you see whatever he’s doing and delays building just to either kill your probe or make it go away, then you’re effectively slowing him down. He has no other choice but to build anyway, and you’ll see it if you keep your scoutin Probe alive.
Save up your Chrono Boosts for Warpgate Research so you can warp in as many units as you can early on. While your Robotics Facility is building, make mostly Zealots. If you’re going for Colossus, make an Observer as soon as you get your Robotics Facility and put down a Robotics Bay as soon as you get the resources to do so. You should do this at around 45 supply so you can do some shock and awe on your opponent with your Colossi.
You may delay Colossus tech for Gateway units and perhaps Immortals if necessary, but you can’t just stay on Gateway units for too long since you’ll be overpowered once your opponent techs up. Once you do get Colossi, never let them engage the enemy without support from Gateway units. They’re actually quite fragile on their own, so don’t let them get caught being on their own.
If your opponent gets counters to your Colossi like dedicated anti-air units, switch to Immortals or Archons temporarily to render them useless. Once you can kill them off, make Colossi again and catch your opponent flatfooted. The problem is the long build time required to get Colossi out, so you have to get your timings right. This build is somewhat vulnerable to air units, so scouting is crucial to spot an early Spire or Starport with Tech Lab.
Take note that on one base, only 225 gas can be mined within a minute, so gas intensive air units and your Colossi will have to come rather slowly. At best, you can come up with one Stalker and one Colossus every minute. Take note though that this applies to your opponent as well, especially if it’s some one-basing Terran. Your Colossus production will be delayed by one when you get the Extended Thermal Lance upgrade, but it will be worth it.
In PvP, it’s safe to say that your opponent will also get Colossi, so you should get Extended Thermal Lance as default in order to not lose out to his range. Once you get to a third base, construct an additional Robotics Facility to increase production. If you notice that your opponent is not adapting well to your strategy, go nuts and give him the finish. If he does get things like Siege Tanks though, switch to Immortals.