I have been messing around with on my Starcraft 2 online game ladder matches lately trying out new builds and SC2 strategy. After watching one of Whitera's 'Secret Tactics' replays, I have been captivated by one of his Starcraft 2 tactics of getting a fast expansion followed by 2 Stargates and massing Void Rays for the Protoss vs Zerg PvZ matchup. It is very surprising how strong and effective this sc2 strategy is.
This is probably an old build first done by GuineaPig in the early season of GSL (probably season 2) where GuineaPig showed the world how effective it is going for a fast expansion on maps such as Shakuras Plateau and then massing Void Rays and eventually switching to Colossus.
It's been around for a while, most zerg are well aware. The grand scheme of 2-stargate play is that you end up with couple colossi to pwn ground army and tons of void rays to defend from corruptors. Infestor with fungal is counter. Also, baneling bust can severely cripple this opening.
As for mid-game void-only push, will only work if zerg is turtling and blindly building roaches, or going double expo. Otherwise, 2-base void ray push has same timing as 2-base hydra or muta, which owns just voidrays.
There is a timing window to punish a droning 2-base zerg with 3-gate+void push @11 min, but it is way different from what you are suggesting.
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