I recently played a game online where I was rushed with cloaked Banshees. While I was able to fight it off, it ultimately cost me the game because I was not prepared for it.
What are the most effective ways to scout early as Protoss? What scouting methods can be used when the opponent walls off his base so you can't get a probe in? Terran and Zerg seem to have it easier with scanner sweeps and overlords being ubiquitous.
Yeah, the best way to scout is to try to keep your initial probe alive for as long as possible. Unfortunately right after your probe dies and your observer gets to your opponent's base there is a crucial time where you don't know what your opponent is doing above their ramp. It's unlikely that your proxy assimilator will be in a good position to see your opponent's tech.
I feel like this is a huge flaw to the game as protoss just have to play blindly. However it's not much better for zerg, they can only suicide an overlord in this early in the game. The overlord dies relatively quickly to marines too so it can be easy to hide one's tech such as in this game between Idra and Silver:
Terrans have the option of using reapers to jump through cliffs, using floating buildings which are either immune to the other races basic unit or have enough life to fly through them, or using a scan, which although it isn't a surefire way of seeing your opponent's tech, it does have a large radius and therefore likely can spot it.
Sucks not knowing whether your opponent is teching or has a mass marine ball :/
One thing protoss can do to even things out though, is to build a pylon in a hidden location far away from both players bases and to hide their tech there.
In the early game, scout with a probe.
In the mid or late game, you can build an observers from your robotics facility and scout with that.
You can also research hallucination in the cybernetics core, then using a sentry, hallucinate a phoenix and send him in to scout.
A real nasty trick, use a probe immediately and go to their base. Then drop two assimilators on their gas... It does two things, lets you watch their base, and tells you when and what they have early as they frantically try and destroy the gas to get to lvl 2.
If you know you are facing a terran, get a probe in their base early and keep it there, running around until they finally kill it off with marines. You should be able to see if they are getting a lot of gas early. If so, then you know they may be rushing banshees or Thor. If you see them wall off, you should be going stalkers or higher tech. In fact, never get zealots against terran anyway since the marauder slow absolutely negates zealots. If you can rush a robotics, you can get an early observer for scouting. Keep 1 probe in front of their base so you can see if they leave it.
