12/12 Reaper opening is the most common build in TvP now. Despite its many merits, Reaper opening is very vulnerable to proxy Oracle due to the low Marine count when the first Oracle arrives. Even a top pro Terran player like INnoVation has looked helpless in such situation. This post suggests a counter intuitive way to solve this problem.
Background
Reaper opening allows you to scout and harass Protoss at the beginning. Its main merit is its ability to scout Protoss’ build even if there is a Stalker. It is a macro build that allows you to expand and shape up to a standard macro game. The general build order is 12 Refinery and 12 Barrack.
There are various variations of 12/12 Reaper opening.
Sometimes a scouting Scv is sent at 15 supply to block opponent’s natural with an engineering bay. This is seen as optional. The purpose is to delay opponent’s expansion. It could be effective if opponent does not get a Zealot and wants to expand slightly earlier. Do not complete building the engineering bay and cancel it at the last second to delay opponent’s expansion as much as possible.
Problem
No matter which build order you go for, you will produce the first pair of Marines after the barrack has gone through a round of Reaper production (one without reactor or two with a reactor) and the build time of a reactor. The first pair of Marines will start training at around 4:25 and complete by 4:50. A proxy Stargate Oracle will be done by 5:00 and reach your base by 5:10 – 5:15. Thus, when the first Oracle reaches your base, you have only two Marines to deal with it, and damage is inevitable. This situation happened in Season 1 WCS Final game 2 on Bel’Shir Vestige between INnoVation and sOs.
INnoVation scouted his opening’s base with the Reaper and noticed that the number of pylons and Assimilators indicated a proxy stargate opening. He immediately moved his Reaper to the common proxy location and found the stargate. He then reacted by building a bunker at the mineral line. The Oracle arrived before the bunker finishes and killed the Marines. The Scvs started to picked off and the bunker could hardly complete. Even if it did get completed, there were no Marines.
What if he waited for the second pair of Marines before he engaged the Oracle? It does not help. A full health Oracle can kill five Marines in a face to face battle without dying. So by waiting for the next pair of Marines ( four in total) which should appear by 5:15 does not make a difference. The game could have ended when the second Oracle arrives in the base by 6:00. Terran just look helpless.
Progamers’ reaction
Based on the example above, there is really nothing much you can do even if you scouted it as early as INnoVation did.
In a game in proleague, Flash scouted Dear’s proxy stargate even earlier than INnoVation scouted sOs’. Flash tried to target the pylon down with the Reaper and Marines. However, that still cannot prevent the first Oracle from appearing.
In this game, Dear built the proxy in a weird location which got scouted really early. The situation would have worked out even better if the proxy location is more normal and not get scouted that early.
Let say you scout the typical proxy location once your Reaper appears and find the proxy stargate. You start to attack the pylon with your Reaper. Assuming Protoss does not react, the Oracle may or not may finish in time depending on the location. It will be really close. However, Protoss can just build a second pylon right away with the Probe still idling next to the stargate and there is no way the Reaper can stop the Oracle from appearing. You cannot send Marines to target the pylon as they won’t make it in time. Protoss can also send a Stalker to the stargate to chase the Reaper off, if the probe is not there. I have seen quite a number of progamers react by building a bunker next to the stargate immediately, but none has made it work. In my opinion, it is a panic move which does nothing.
How about building a turret? Sure, there is a +1 upgrade Reaper opening variation with an early engineering bay, which both Flash and Bbyong had used it in WCS Korea. In the Flash vs. Dear game, Flash did start an early engineering bay but the turret cannot finish in time . Even when the turret does get completed, the damage is done.
Proposed solution
The proposed solution is to build an engineering bay and a turret.
What are you talking about? Didn’t you say it doesn’t work?
I am referring the engineering bay that is used to block at opponent’s natural and not the early engineering bay that is part of the build. Usually, you do not finish building the blocking engineering bay and cancel it at the last second when Protoss tries to destroy it and expands. To counter the proxy Oracle, I propose finish building it. This may sound counter intuitive, but I will explain why.
It is important to highlight that it is not a blind counter by finishing the blocking engineering bay. Here is how you do it.
Send a scouting Scv at 15 supply and build an engineering bay at opponent’s natural. The blocking engineering bay starts building at around 3:20. Note that it takes 35 second to complete. Pause building the engineering bay when it reaches around half of its required build time (around 3:40), and use the Scv to scout opponent’s base. Count the number of pylons and assimilators to look for sign of a proxy stargate. If there is only one pylon and two assimilators with three probes each, it is [extremely likely] going to be a proxy stargate. Move the Scv back to the natural and complete the engineering bay if you think it is a proxy stargate. It should complete by 4:30 depending on the time that the Scv took to scout. Then, build a turret in your mineral line, which completes in 25 second. It should finish at around 5:00, which makes you safe from the Oracle (arrives at 5:15). Although you do not get the 94 mineral back from cancelling the engineering bay, the amount of damage reduced in your base is much more significant.
Furthermore, the Reaper appears at 3:30 (assuming it is not reactor then double reaper build). If you move the Reaper to scout the key proxy locations straight away, you should scout the stargate. This can help to confirm if it is indeed a proxy stargate. To make things better, rally your barrack to the turret to prevent the Oracle from picking them off before you have more than five Marines.
Summary
It is possible to not take serious damage from a proxy Oracle build using a 12/12 Reaper opening.
Step 1: Scv scout at 15 (can be 14)
Step 2: Build an engineering bay at opponent’s natural
Step 3: Pause building the engineering bay at around half of its build time and scout opponent’s main base
Step 4: If there are signs that indicate a proxy stargate, complete the engineering bay.
Step 5: Build a turret in main base.
TerranCraft 
This seems like a very interesting response! but would’nt it have a lot of problems with an opponnent going Zealot into proxy Oracle, and Wouldn’t it be better to scout first? Otherwise you would always have an ebay, even against someone going Zealot stalker expand
If there is a Zealot, and I think it will work on the engineering bay at the natural, so probably it may put stress on completing it. However, I have not experienced it yet.
If you scout right away and not put down the engineering bay, then it lost its purpose. Let say, you scout that he’s doing a proxy stargate, you would rather build the engineering bay at home instead of going back down to the natural to build it.
The main strength of this reaction is that it doesn’t affect your build order. It is an option that you can do if you scout that he’s going for a proxy stargate. If he doesn’t, just cancel it as usual.
By scouting I was just meaning poking in the main to see if he makes a zealot btw
I think this has a lot of genius to it. I didn’t expect it to be the solution! Cool thinking and I hope this gains some traction and I see it in a WCS game.
If he makes a Zealot, it will attack the engineering bay. So you’ll know.
What I propose is to build the engineering bay to block first, then go into the main to scout.
So, why don’t build engineering bay at your base and stop it at a half? Scout opponent. If he proxy stargate. Finish EB and go for fast upgrade 1-1. If he doesn’t, continue EB for 1-1 or cancel it for factory go on.
First of all, the purpose of the engineering bay at opponent’s natural is to delay his expansion. When you build that engineering bay in your base, it won’t have that advantage.
An engineering bay at that timing (before your command centre) will delay your expansion. To have it built at opponent’s natural, it delays opponent’s expansion more than yours. It is a trade.
When you build it at that timing in your base, you’re behind since it delays your expansion. The point is that if you blindly build an engineering bay at your base, and opponent is not going for proxy stargate. It doesn’t seem like a good trade. The proposed solution is a reaction and not a blind counter.
This build is used against me so often that I’ve been throwing the engineering bay down in my base as soon as my reaper scouts the base and notices something fishy… there have been a few times where it wasn’t proxy oracle and I was wrong…but most of the time my turret gets completed just in time and even sometimes I kill the oracle with the 2 marines
When you said you killed an oracle with marines, is the oracle taking damage from the turret? This is because it takes 6 marines to kill a full hp oracle.