In my last match, I had a group of 10zealots+6stalkers ready to go for that purpose and they were wiped out as soon as I left my base by ~15 zerglings and 6~8 hydralisks that were burrowed just beyond the chokepoint
That was at least partly my fault, I didn't realize how many zerg units could burrow now and didn't have an observer up to go with them yet. But still, it's not like I dallied around...
I get concept ideas and basic execution but I always manage to lose control somehow about 15 minutes in. After that harassing force was wiped I was just beyond help, stayed behind the curve the whole time. Lost another assault group in almost the same fashion (wasn't an ambush though, in fact I technically got the drop on him), and then had a major force (20ish zealots, 10ish stalkers, 6 or so colossi) built up just in time to have his assault group come and wipe me out.
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