TvT: 15/16 Reaper Expand Basic Framework

In the last post, I discussed how TvT is a match up of framework, and why there is less emphasis on build orders. This post follows that up and provides a basic framework for the standard 15/16 Reaper expand opening.


The Terran mirror match up requires players to adjust and adapt to each other’s decision, and hence, it is about relativity. This then makes it hard for players to prepare with a planned build order, because you cannot strictly follow one and expect to work. Although it is harder to plan for TvT, there can still be a framework.

A framework is basically a guide that tells you, “if opponent does this, I do this.” It is essentially having multiple build orders based on the same opening, and you pick a build order according to opponent’s openings. This post focuses on the 15/16 gas first Reaper opening.

15/16 Reaper opening

In comparison to other Reaper openings, the 15/16 gas first Reaper expand is developed relatively late. When we talk about Reaper expand, it is usually 16 Barracks and 16 Refinery. Nowadays, both 16/16 and 15/16 are heavily adopted in the metagame, but 15/16 is definitely the more popular one in TvT.


14 – Supply Depot
15 – Refinery
16 – Barracks
@100% Barracks – Reaper and Orbital Command
@400 mineral – Command Centre
@100 gas – Factory
@100% Reaper – Reactor*
@100 mineral – Supply Depot

The above notation is the core of the 15/16 Reaper opening. I put an asterisk on the Reactor, because you cannot afford to make an add-on in certain situations and I will explain it later below.

Comparison with 16/16

The main reason that 15/16 is more popular in TvT is the quicker Factory at the cost of one or two early Marines. The Factory is placed down when the Reaper is not even out yet for 15/16, but the 16/16 does not even have 100 gas when the Reaper completes. Given that it is paramount to get 1-1-1 early in the game as it dictates the initiative and subsequent options, a quicker tech opening is generally favored unless it sacrifices much of the economy. In Legacy of the Void, the Barracks is no longer as delayed as it was in Heart of the Swarm when you go for a gas first opening. Also, as you can see from the vod below, the timing of the Command Centre is almost identical for both openings.

Reality, who used the 16/16, made a Marine after the Reaper, and did not build a Reactor immediately. This is to allow a quicker Factory, which is still later than the 15/16’s. That extra Marine is not useful at that point of time, and the quicker Reactor for 15/16 means that the Marine count for 15/16 will catch up anyway. Therefore, it is safe to say that 15/16 is superior to 16/16 for Reaper expand in TvT generally.

There is a trend that the 16/16 opening makes two Reapers, as there is a small window that you have one more Reaper than the 15/16 opening and you can get an advantage from it. Below are some examples of that.


Like I have said in the last post, 15/16 Reaper expand is the best opening to illustrate how a framework works. As the name suggests, the opening has a Reaper and expands rather early. This gives you the perfect ground to develop a framework. You have a Reaper, which provides you scouting information to decide what to do. You expand early, and that means you have to rely on being able to pick the right reaction to get ahead.

I will discuss how 15/16 can be played against the common openings that I have mentioned in the last post. The framework assumes that you do a normal Scv scout at 17 or 18 supply, and you are able to get information at a normal time.

Multiple Barracks Reaper

You are clearly the defender against a multiple Barracks Reaper opening.

The opponent is doing an offensive opening, so you have to react with your opening and not build order. Obviously, you have already decided to do the 15/16 Reaper expand opening, so you cannot exactly change the opening itself. However, you can make adjustments to the later part of the opening based on the scouting information you gathered.

There are two ways to know opponent is going for multiple Barracks Reaper opening. First, and the most straightforward one, you see more than one Barracks and a Refinery is taken. Second, you see only one Barracks and one Refinery, but opponent doesn’t expand at the one Barracks expand timing. This signals plausible hidden Barracks (maybe proxy), and you should assume it is multiple Barracks Reaper.

What is the timing of the Command Centre for a one Barracks expand? It is usually 1:40. But like I have said, it is a matter of relativity. So when you have 400 mineral for your Command Centre, and opponent has yet to put down one or at least attempt to, you know the mineral has to be spent somewhere (i.e., more Barracks).

How do I know whether it is a two or a three Barracks Reaper? You react more or less the same way for both in regards to production decision making. A way to tell is to look at the timing of opponent’s Refinery. Generally, a three Barracks Reaper uses a 15 gas, and a two Barracks Reaper uses a 16 gas. Since you are using a 15 gas yourself, you can click on your Refinery and opponent’s. If they are almost identical, you know opponent is 15 gas, which means it is likely to be three Barracks. If you mined about 50 gas more than opponent, then it is likely to be 16 gas.

The above two vods are examples of 15/16 Reaper expand against two Barracks Reaper. It is uncommon to see three Barracks Reaper in professional games now. I believe Dream’s reaction is spot on, and I have briefly discussed this in the last post.

First, he built his Command Centre on the high ground, and this reduces the area he needs defend. Second, he gets a second Reaper and a Hellion, which are the best units against multiple Barracks Reaper. The goal is to stabilise by having as many units as possible, so you should not make an add-on (refer to the asterisk in notation above). After Dream made a second Reaper, he continues to make Marines as he wants to have more units. The reason to not get a third Reaper is to have enough gas for a Starport to converge back to your standard 1-1-1 set up.

Hellions are the best counter against Reapers, so you want to hang on with your few bio units to get the Hellions out. Once you get two to three Hellions, opponent’s Reapers are less effective. Thus, your opponent will want to target down your Hellion and snowball the advantage with more Reapers. It becomes a battle of micro, so there is nothing much to talk about. With that being said, I recommend pulling three to four Scvs to defend against the Reapers, and it is alright to lose a few Scvs in the process because that is the trade off for the aggressive versus economic openings. Your rally point of the Factory is important, and you can repair your Hellions with Scvs.

The next step is to know whether the aggression is over, and you have to make a decision whether to counter attack. The decision is easy against two Barracks, because you know you have more than enough against that five to six Reapers after you have three Hellions. However, against three Barracks, it is harder to know whether the opponent is still committed to Reapers or s/he started to transit. You don’t want to move your units across, and have the Reapers jump back into your base and destroy every Scv. My rule of thumb is that if it’s proxy Barracks, just keep being defensive and macro. I am already ahead just by defending. If it is not proxy, you will need to make a judgment by how many Reapers you may have killed and how many you see in the next wave. You should also scan in between the natural and main of opponent to look for the Command Centre.

Counter attacking is important against multiple Barracks, because there is a window that you have your 1-1-1 units but opponent doesn’t have the tech. This switches the players’ role, and you are the offender now. A simple way to counter attack is to move your Hellions across and load your Marines into the Medivac. In sum, do something with your Hellions on the other side of the map, because it is hard for opponent to deal with them.

Subsequently, you want to transit into your main composition by putting down additional Barracks for bio, or additional Factory for mech. In the above vod, GuMiho went straight into Banshee, because the Reaper aggression ended early and he wants to go for mech.

In the vod below, although Bunny did not use a multiple Barrack Reaper, Cure wasn’t able to get a normal Scv scout into the main as Bunny built an early second Supply Depot to wall off. It is uncommon to have a second Supply Depot that early unless you go for multiple Barracks Reaper. Consequently, Cure decided to play it safe and treat it as if it is multiple Barracks Reaper. The adjustment he made is similar to Dream’s. The combination of not having Reapers coming to his base and seeing the Command Centre at Bunny’s natural (send the Scv back in) tells Cure that it is not multiple Barracks Reaper, and he then decided to converge to his game plan. He went straight into Banshee, which is a common path for mech. Anyway, I show this game to highlight the similarity of Cure’s and Dream’s reaction.

Gas first fast tech

Again, you are the defender, because you have an earlier Command Centre and later tech.

Unlike multiple Barracks Reaper, gas first fast tech does not require immediate adjustment in opening, so it is a later build order adjustment. Thus, you can carry on with the basic notation above, and build the Command Centre on the low ground. The question is what units you should get to defend the imminent attack.

How do you tell it is a gas first fast tech? When the Scv scout saw a Factory being built right after the Barracks and there is only one gas taken, it has to be a gas first opening without Reaper.

Broadly speaking, there are two types of attacks. One is single Refinery, and the other is double Refinery. Single Refinery is usually a drop with Marine, and a mix of Hellion and Widow Mine. On the other hand, double Refinery has more variations, and they are usually more Tech Lab focused. For example, it can be cloaked Banshee, or early Tankivac harass. A Tank push is also possible, but very rare. The key is to make use of the Reaper and collect information on what type of attack opponent is planning.

There are many ways to play against a Marine drop harassment variation. But in my opinion, there should be at least either a Viking or a Cyclone in the preparation (you can have both). This is because you are fine with trading units more or less equally since you are the defender (i.e., economical advantage), but you don’t want to let opponent keep picking up units to harass. The focus is on damaging the Medivac as much as possible in the exchange (kill it if you can), and that basically ends the attack. A Viking or a Cyclone does that job well. The rest is positioning and having the map awareness to anticipate the drop.

In the vod above, TY was using 15/16 Reaper expand against Maru’s gas first fast tech, and TY knew what he was up against with the Scv scout. He followed the above basic notation, and then made his adjustments to be defensive. TY swapped the Factory onto the Reactor for Hellions, which are good against Marine drop. Since he is making Reactor Hellion, he cannot make Cyclone. Thus, he makes a Viking for defence. As you can see, once the Medivac was damaged enough, Maru had no choice but to stop attacking.

In the vod below, TaeJa was using a 16/16 Reaper expand against gas first fast tech. Even though he isn’t using 15/16 Reaper expand, the relative position against gas first fast tech opening is the same for both Reaper expand openings. TaeJa used his Reaper and tried to deduce what Ryung was trying to do, and the Marines and Hellion signal that it is likely to be a Marine drop variation. He subsequently set himself up defensively against the drop, and had a Cyclone. TaeJa could choose to not make a Viking, because he had a Cyclone.

One thing to note about gas first fast tech drop builds is its follow up attack. In both vods above, there were another follow up attack with Banshee, so you should not assume the aggression is over after the first drop attack. If your Reaper is still out there, sneak it into opponent’s main when the first drop moves out. This allows you to know what the follow up is.

I cannot find any recent vod that has gas first fast tech into two Refinery, so it shows its low popularity. Anyway, the most common build is Banshee, and you can make a Viking and Missile Turrets. Alternatively, you can also get a Raven, and use Marines.

Gas first double Reaper and Hellion

Another popular but less discussed opening is the gas first double Reaper and a Hellion pressure, and it is a mini snipe build against the common Reaper expand openings. It goes with a gas first opening, then a second Refinery at 17. The extra gas allows you to put down the Factory and make a Reaper when the Barracks completes. The aim is to take advantage of the superior unit count with two Reapers and a Hellion in that small time frame. Therefore, you are the defender in the opening phase.

The vod below shows you why it can work well against Reaper expand.

The two Refineries basically give away the information about this build. TaeJa played it out well after he scouted it in the vod below, but I think there is room for improvement. He sent the scouting Scv and Reaper to the bush in the middle to anticipate Ryung’s Reaper, and I think that is good move. However, once he didn’t see the Reaper coming, he should have moved the Reaper back to his base. In the game, Ryung’s Reaper took another path to TaeJa’s main, and the Reaper could be a problem because TaeJa only had a Marine. TaeJa made the right decision to keep making Marines rather than a Reactor, and in my opinion, he could follow the same approach used against multiple Barracks Reaper. The key is to have your units in the main, and don’t allow the Hellion to get into the main. If you can isolate the Hellion, you are not worried about the Reapers jumping into your main because you have the same units.

Reaper expand

I group both 16/16 double Reaper expand and 15/16 gas first Reaper expand as Reaper expand in this discussion. The key is to not lose your Reaper, and you will be fine to carry out with your build order. The interesting thing is either of you can take the initiative and be the offender.

If you choose to be the offender, the most extreme attack you can do is six to eight Marines, three Hellions, one Reaper and one Medivac attack. TY used this attack in a 15/16 Reaper expand mirror against Ryung in the vod below. He loaded up six Marines in the game, but you can wait for that few seconds and load up eight.

However, things can get messy if both sides decide to do the same thing, and it comes down to who has the better engagement. In my opinion, it is better to switch the second of the three Hellions for a Widow Mine. In Heart of the Swarm, gas first Marine Hellion drop variation also has this minor thing that you can either go for three Hellions or two Hellions and a Widow Mine. The reason I think the Widow Mine variation is better is not to have a better engagement, because I think three Hellions should do better in general. The reason is to allow you to do a Widow Mine Marine drop, and defend with your Marines and Hellions in case opponent is attacking too.

A drop with six Marines and a Widow Mine is more of a harassment than an attack like the three Hellions version. It definitely can do lots of damage if opponent is going to attack everything they have and leave nothing at home. You can use the two to three Hellions, Marines (continue production) and Viking to defend your side using your defender advantage. In my opinion, this is the best production and tactical choice for this mirror situation, and I have talked about it in an old post.

In the vod below, TY adopted more or less the same approach by attacking with only a drop of a Widow Mine and Marines, and set up defensively after that. He chose to use a Tank instead of Hellions, but the general idea remains the same.

If you are going for mech, Reality’s choice in the vod below is a solid choice as well.

What to do next

The above discussion provides a framework of how you can approach the match up with a 15/16 Reaper expand opening. After you have deal with the early stage of the game based on your planned framework options, you can simply converge back to your convergent point by adding the necessary structure. Like I have said, it is difficult to have a detailed build order in TvT, so it is very hard to suggest the best way to move to the convergent point.

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4 thoughts on “TvT: 15/16 Reaper Expand Basic Framework

  1. This is such excellent work, again! I am speechless how much effort you put into it. You also pointing out who is the defender and attacker while helping the reader to learn it himself by showing him your reasons. Please, let me donate. TY gg wp

  2. Thanks for the support as always. I took your advice and put up a PayPal button at the side. Please don’t feel obligated to contribute, as it is completely voluntary.

  3. Max, can you make a complex post about scout in TvZ and TvP. Almost the only reason I am loosing games is a bad scouting, I feel like I understand really a little in that area so I loose often to protoss all-ins or any un-standart play. Maybe some “scouting-patterns” will help for beginners: like if you see theese buildings, 2 base, 3 gas and such units probably he goes for… and a few good decisions would be… I’m watching A LOT of streams and premier tournament games, would probably guess that it’s enough to understand what and how to scout and react but… not really, I feel just powerless in scouting. Such a post would help a lot. Thank you very much.

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