A loyal friend of the Swarm
I think the first game where it really hit me was Flash vs. Jaedong in the MSL quarterfinals (shockingly, it's Blue Storm)
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Being the idiot I am, previously I thought that this kind of non-stop mutalisk mayhem was just [insert zerg player here] being skilled with his muta micro. I can't believe it took me so long for it to really hit me just how awesome Blue Storm is for mutalisks. I am such a noob sometimes (okay, most of the time).
Anyway, the mutalisk harass here isn't perfect, but it's damn good. Flash is forced to spend over 1k minerals on turrets alone. Meanwhile, Jaedong takes a third gas, then a fourth, and then a fifth, and by the time Flash gg's out, Jaedong has 5 fully productive bases, and his sixth base is morphing his 6th gas. This is also the first instance where I noticed the guardian build, and associated it with Blue Storm.
In fact, the idea of using guardians on Blue Storm is older than that. After a bit of research, I discovered that in Blue Storm's very first televised ZvT, YellOw[ArnC] vs. Canata, Yarc gets guardians. Oh, it's not even close to the refined Blue Storm build we see today. But it's clear that even when Blue Storm was first introduced it occurred to zerg that the terrain around the natural was so favorable to harassment, that getting guardians was viable.
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Part 2:
Part 3:
Clearly, this is not Jaedong's trademarked 3 hatch muta harass into 3rd gas into hive tech build. But it's pretty cool to see guardians come into play so early in the map's history. As far as I can tell, the first time this build really took off is when Jaedong used it to beat Flash in the MSL quarterfinals. Now, it is being frequently copied, and Terran has yet to find the best way of dealing with it.
The first attempted counter to this was 2-port wraiths, again Flash v Jaedong. While Flash lost that game, it's not really his fault, because he was really far behind on expos anyway. Later, in the group stages of the GSI, he played against Savior, who also tried the muta harass into guardian build. In a moment of inspiration, Flash redeveloped the "Eraser" (irradiating his own science vessels), and broke Savior's attack just when it looked like Savior had Flash dead to rights. Judging from this, it looks like early science vessels is the best counter to early guardians.
In short, mutalisks kick ass on Blue Storm. I told you I'd be stating the obvious.