Foreword: Let me be very candid! This is going to be another guide from Terran perspective because the author is a dedicated Terran player. But I promise in the near future, I will take time out to compose strategy guide from the perspective of other players (hopefully that will slake their bloodlust against me :P) but for now bear with moi and read on!
Zealots are thy enemy!
At a glance the heading above seems to be a quote from some religious scripture but its just me trying to sound eloquent and giving a warning to watch out for Zealots.
While playing as a Terran and facing off against an opponent who has chosen Protoss, the thing to bear in mind is that Protoss players can overwhelm you early when your defenses are bare minimum by sending in a lot of zealots. Terran players can counter this situation by having around 4 barracks for speedy production of marines and using bunkers to safeguard the barracks while they are still in production.
Vigilance is the key to success.
A Terran player has to be vigilant and proactive throughout the face off and it is highly recommended to send out scouting parties on regular intervals to check for enemy troops heading towards your base and to see if the Protoss are trying to climb up the tech tree to produce Reavers. So how can you tell if Protoss are ready to produce Reavers? Carefully scout the base for cybernetics core building or robotic facilities, if you see one of these buildings than you can rest assured Reavers will be coming your way soon.
Repealing Zealot attack
But first you have to prepare for the most basic zealots attack. Now it is entirely up to the player’s discretion to play offensively to repel the attack or adopt a defensive stance to safeguard their base. If you decided to take the offensive approach you should have around 4 barracks and 3 supply depots ready while continuing production of SCVS. The key to surviving this round is placing bunkers around your key buildings so make sure your barracks and supply depots are not spaced out, they should be close together in a group formation with bunkers surrounding them. Don’t forget to place at least 3 to 4 marines inside the bunkers and conserve the minerals to continue building marines, bunkers and SCVS.
As mentioned before vigilance is the key to surviving this encounter. It is imperative that you send out a few marines for scouting purposes and keep abreast of what your enemy is doing, whether it is expanding its reach or more importantly sending an attacking squad towards your base. It is also advisable to build bunkers and populate them with marines in the path of the most probable enemy route.
Firebats to the rescue!
Assuming you have survived the first wave of attack get ready to mine gas and quickly establish an academy and research stim packs. Like the Zerg rush counter strategy you would need a substantial amount of Firebats to kill the rushing zealots and when your Firebats are backed by the stim pack research they will wreck carnage over zealots. Stim packed marines and firebats combination will let you hold off and even gain an upper hand over the enemy if your forces are outnumbered. The Protoss will be put on back foot and forced to retreat and research Dragoons to counter the firebats but till they do that you would have plenty of time to refortify.
Defensive playing under such circumstances might be a little tricky as you would find yourself hard-pressed to harvest enough minerals to afford to build bunkers. Bunkers are essential for protection of your SCVS.