I've been playing as 'toss and have been doing fairly well (6 wins 3 losses so far today) but every time I get rushed by marine/marauders I always fail. I can't seem to spot it in time and never have enough Zealots up to defend from it.
Any tips for repelling a marine/marauder rush?
Really depends on the map. For something like Lost Temple where you have reasonably narrow locations, get a few sentries in your army mix so you can throw down some forcefields and cut their army in half. Taking advantage of choke points and not letting the terran army get any sort of reasonable surround is essential if you're only using gateway units. On more open maps you need to be careful with positioning, as terrans are unreasonably good at kiting, especially with concussive shell on marauders. That's where sentries come in to block off any retreats.
Also be aware marauders eat through stalkers like paper, so it's useful to tailor your army accordingly. Heavier on zealot for more marauders, or a few more stalkers vs marines as a very general rule. (be aware that concussive shell can effectively nullify even charged zealots without sentries to back them up).
I personally enjoy a 2 gate robo opening vs terran, so you have the option of getting out some immortals to help deal with heavy marauders and observers for general scouting and detection vs banshees/ghosts etc.
Either that or just DT rush


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