Original image by Alexey Mikhaylov (Arpeich) 

The mech-bio composition for TvZ is extremely popular among progamers now. It is revolutionary in the match up and readers have told me to make a post for it. So here it is.

The first thing I did when I was told to blog about this is to check if it’s a one game thing or it’s a persistent trend. If you’re a frequent reader of TerranCraft, you probably would have noticed that I tend to analyse trends instead of a specific game. There are reasons. First, it is more constructive to observe trends than cross-sectional games. Second, it is more analysable since I can better deduce and make sense about the choices made. Third, it is more topical, which makes it more interesting. Thus, if I did not make a post for a specific game that you email me, it is not that I don’t care or I think it sucks. I simply mark it down and observe if it’s part of a trend. Hence, this post is directly related to this suggestion by FlaSh (a reader, and not the you know who).

Background

It is best to briefly go through the basics of Terran composition in TvZ in order to appreciate the reasoning behind this new trend. Often you hear commentators say Terran is going “bio” or “mech”. To be exact, it is not exactly a categorical thing in a mutually exclusive sense, whereby you either go bio or mech. The best way to illustrate this is to conceptualise Terran composition in a continuum. That is, it is not black or white, but simply shades of grey. Like the figure below.

The plotting is not done to scale obviously, but it is enough to get the idea across. Also, you can mix in other counter units accordingly in any composition, but the above ones represent the usual core of a Terran army.

On one end, you have the “purest” bio with no units from the Factory. On the other end, you have the full mech composition with no units from the Barracks. Most of the time, a mixture of the units in the middle of the continuum is used. The difference between mixing in Widow Mine, Hellbat or Tank into the basic bio composition shift the position of the composition on the continuum. Widow Mine is “more bio” than Hellbat or Tank because armory upgrades benefit it the least compared to the other two. Although the focus of upgrade is on the Engineering Bay for these three compositions, the relative weighting in the reliance of Armory upgrade is different. Also, the mobility of the composition is another factor of the relative position on this continuum. The bio end represents the most mobile and the mech end represents the least mobile. Therefore, the key factors to determine the relative position of the compositions on this continuum are the focus of upgrade and the mobility.

The new composition, which is of interest in this post, is the most middle of the road of all compositions. Despite many gave credit to FanTaSy’s recent game against Life in Proleague for the rise of this trend, MarineKing should be cited as the first who utilised it in a notable pro level game in 2012 (leave a comment if I’m wrong). He started with a mech composition, then put down four Barracks for a mixed composition (I cannot find the vod). He basically replaced Hellions with Marines in the Wings of Liberty mech composition.

The composition

The mid game main composition is made up of Marines, Marauders, Medivacs, Tanks, Thors and Hellbats. In another words, both the main components of a pure bio and a pure mech composition are used. As for the sequence, you get Mech first, then add Bio into the mix. Importantly, you get upgrade for both bio and mech. Subsequently, you can move along the continuum by adapting to opponent’s composition.

 

Why do this build?

My understanding is limited, so feel free to chip in your opinion in the comments.

Typically, Terran go for either bio or mech focused, and Zerg have very specific reaction based on these two compositions. Zergling, Baneling and Mutalisk is the standard go to composition against bio, and it is arguably not the best answer against mech. Zerg have two main reaction routes against mech. The first is to go for Mutalisk to force Terran to make Thor, then transit to Swarm Host which is good against Thor. The Mutalisks do not only pin Terran in base to buy time for Zerg to transit, Zerg can also spread creep unopposed. This makes Swarm Host even more effective afterwards. The second is to go for Roach and Hydralisk timing attack, but this is restricted to certain maps that have a wide area to form a good concave.

One of the main objectives of this build is to confuse the opponent. As mentioned earlier, this is a mech then mech-bio transition. Thus, Zerg will likely do one of the above two choices that is intended to fight mech. However, neither is effective against a bio and mech mixed in this build. Swarm Hosts are not effective against bio because of their poor mobility. Unlike a standard pure mech build, this build allows you to get close and kill the Swarm Hosts while dropping somewhere else on the map.

The key is to let Zerg think that you are doing a mech build. Therefore, it is important to hide your Barracks and bio units.

How to get there

I’m not going to list the build order as this is not necessary. The key is the convergent points.

You can choose any common opening as long as it can reasonably converge to the first convergent point
– Reactor Hellions
– Banshee
– 3 Command Centre

This is a standard mech early convergent point. Given the current metagame, the most common opening is 12/12 Reapers. A proxy Reaper expand is doable too. The next convergent point is to add two more Factories to make it three. Simple.

Then, you have the first notable cross junction. You choose one of the two choices, add
– 2 Armory + 1 Engineering Bay
– 1 Armory + 2 Engineering Bay

Clearly, the first option is more mech focused and the second option is more bio focused. Eventually, you still need to get full upgrade for everything. Yes, everything.

After you put down the upgrade buildings, start your upgrade and continue mech unit production. This is important. You will not have the resources to build Barracks and Factories, and produce from them simultaneously, and defend the third. The primary focus at this point is to get the key upgrades (stim and the level one upgrades) and defend the third. At the same time, you need to sell the story that you are doing mech by running your Hellions around to clear creep and attacking Overlords with Thors.

Next, when you have enough resources, throw down six Barracks. One less if you are more mech focused.

So the next convergent point is
– 3 CC
– 3 upgrade buildings (Armory and Engineering Bay)
– 3 Factories
– 7 Barracks
– 1 Starport

Prepare to push out with Marines, Medivacs, Tanks, Thors and Hellbats when you almost have +2/+2/+2 (Stim and Combat shield should be completed). Subsequently, just play out a standard game accordingly. With the production structures and upgrades, you can afford to hop around to get the right counter composition against Zerg.

Critique and concern

Although this is relatively new, it is popular enough that the Zerg players will not fall for the composition trap blindly. However, as you can see from the recent games, Zerg have yet to find an answer to this build.

One weakness I can think of is the transition period. Terran is weak between 11:00~ and 13:00~. The resources are being spent on upgrades and multiple Barracks. If Zerg commit to an attack at this point, Terran cannot hold. However, there is mind game in this. The opening is the same as a standard mech build, so Zerg may not dare to hit a timing in this time frame since it is suicide against a pure mech build.

Another weakness is relative early Broodlords and Vipers, which EffOrt used against Maru recently. There is no extra resource to build additional Starports and produce sufficient Vikings to deal with the Broodlords.

Whether the first push with this mixed composition is stronger than a standard mech push is debatable. If it is weaker than a pure mech push or just equally strong, then it is difficult to justify the transition weakness mentioned earlier. The primary concern I have with this composition is the cost efficiency of upgrades. The amount of resource spent on upgrades for both bio and mech is an opportunity cost for the units you can produce to leverage the upgrade value of focusing on just one side. It is like economies of scale. The cost of upgrade is fixed, and hence, the more units you produce that can benefit from the cost spent on the upgrade, the higher value in return you get from the units.

Moreover, even though I mentioned earlier than you can switch between bio or mech focused in the late game. Zerg is likely to be the one with composition advantage in terms of countering each other’s composition. Larva system is the best tech switch mechanism in the game. Therefore, it seems a bit optimistic to suggest that the flexibility to move along the composition continuum is a strength of this build. Nevertheless, there is still much room to improve.

I must say this is a big innovation in the match up. It literally changes the whole dynamic and understanding of TvZ. Starcraft is awesome.

For learning purposes, I recommend watching the following vods as they are more “standard” and capture the essence of this build better.