[G] Zerg Sim City for Spire protection in ZvP

Greater Spire is the most important tech structure to defend because
1. Broodlord(BL) is essential for late game army composition vs Protoss.
2. It takes 100sec to make spire, additional 100sec to morph into Greater Spire =200sec to remake greater spire. Most other tech buildings take only 60 or so seconds to remake.
3. It costs 200 200 + 100 150 = 300mineral 350gas to remake. Gas cost is significantly higher than other tech buildings when you remake.

2nd one is probably the biggest reason. It also takes 34sec to morph from corruptor to BL, so it actually takes 200+34 =234sec=almost 4minutes before you can remake BL. Not having to worry about BL remax for as long as 4min is a huge advantage for Protoss. Sure, losing Spawning Pool, Roach Warren, or Infestation Pit hurts as well, but not nearly as badly in terms of both building time and cost.

As simple as it sounds, walling-in your greater spire is the best and easy way to defend it from melee units. Without surface area, melee units such as Zealot/DT cannot attack it. Recently, some Zerg players started to do so. However, very few seem to understand walling mechanics in SC2. It is important to know that a 3X3 building DOES NOT occupy area covered by 3X3 square. It actually occupies area covered by the octagon inscribed in 3X3 square.(Footprint Type A in the image below) Spine crawlers and spore crawlers use even smaller octagon(Footprint Type B) unlike similar 2X2 pylon/depot which use Footprint Type A.



Because corners of building grids are NOT blocked by buildings, relatively small units like Zealot/DT can get through in between badly placed 2 buildings, which sometimes go against intuition and graphics. Your walling experience with Protoss/Terran play does not help either because spine/spore are smaller than pylon/depot.

After hundreds of experiments, I found some common combinations of buildings that fail to completely wall-in greater spire. Hole 4&5 in image must be counterintuitive to most players.



These wall-ins are probably good enough in real game situations. A hole that lets only 1 zealot attack is hardly a big problem. However, there is a better way to wall-in without having to invest more. When there is a better way, why bother trying suboptimal wall-ins?

There are 3 ways to completely wall-in your greater spire that I could find.
One is what I call “Windmill Arrangement,” the best way.
The other 2 are asymmetric way with spine/spore as a part of the wall.



In-game images
Clockwise Windmill Arrangement
+ Show Spoiler +
Counterclockwise Windmill Arrangement
+ Show Spoiler +
With spine/overseer
+ Show Spoiler +

Those 3X3 buildings looked like sails of a windmill with greater spire as its axis, so I thought windmill arrangement was a nice way to denote what I consider will be the standard play in future. Windmill arrangement is the best way because of several reasons:
1. No spine/spore is used as a part of the wall. Least health for 3X3 building is 750 for evolution chamber, which is still much higher than spine/spore(300/400). 850 health is standard for Zerg tech buildings with 1000 for Spawning pool being the exception and highest.
2. Any 3X3 building spawns 6 broodlings when it dies. These 6 broodlings buy time for as much as 8 seconds unlike spine/spore which doesn’t spawn any broodlings. Extractor doesn’t spawn broodlings, but gas location is impassable anyways.
3. One of the 4 3X3 buildings can be an extractor. In fact, I recommend using extractor as one of the 3X3 buildings because defense for greater spire around the wall-in also defends hive/mineral line/gas effectively.
4. If you do a build that makes a 3X3 building after spire anyways, then literally no additional investment is required to complete this wall-in. Baneling nest, Ultralisk Cavern, or 2nd Evolution Chamber comes to my mind for example.
5. Complete wall-in prevents protoss from target firing greater spire. If he does, then AI gets confused and zealots/DTs dance around the wall. Also, shift-click target firing doesn’t work well either. Shift-clicking one walling buliding first to greater spire second lets those 6 broodlings buy full 8 seconds before zealots/DTs can start attacking greater spire because shift-clicking beforehand prevents them from killing broodlings that push them back.

Whenever there are pros, there are cons as well. However, I believe pros of windmill arrangement outvalue cons. Following are possible cons and my answer.

Con No.1: Your spire location becomes predictable once you prepare other buildings for it.
When you want to do hidden mutalisk tech switch, then probably hiding your spire now is more important than making at better defendable location for later. Other than that, going broodlord in lategame ZvP is no secret. An observer or hallucinated phoenix can find a “hidden” spire location in your base quite easily as well.

Con No.2: Having multiple tech buildings at one location has a risk of losing them all together.
I agree, but at the same time, you only need spine forest at that particular location rather than everywhere in your base. Also, non-greater spire tech buildings are much easier to rebuild. Losing them is not as big of a problem.

Con No.3: You need to invest in a 3X3 building to complete the wall-in after making spire.
Yes. If you have no plan to make any more 3X3 buildings after spire, then it is the investment you wouldn’t have to make otherwise. I usually make 1 evolution chamber to complete the wall even if 3-3 upgrades are already done because evo chamber is the cheapest 3X3 building. In fact, evo chamber is cheaper than 1 spine crawler. I believe 1 evo chamber wall investment is more worth than 1 spine crawler at that stage of the game. If you are rich enough in mineral, making 2nd spawning pool isn’t that bad of an idea for extra 250 health and vs pool snipe.

Con No.4: When extractor is used as a part of the wall, a 3X3 building next to it partially blocks gas mining route.
You always need to carefully choose clockwise windmill arrangement or counterclockwise one depending on the angle of the gas. Sometimes, wrong choice delays gas mining by a lot. I found that counterclockwise version works more often than clockwise version because of current map making tendency.

As long as you have decent response, windmill arrangement + spines around are usually enough to deter small Zealot/DT attacks. However, greater spire does die if you don’t have enough spines for DPS or you couldn’t respond in time. So, let’s find out how many seconds windmill arrangement buys compared to exposed greater spire.



When only 2 zealots fit in vs greater spire at Step 2, then it dies in 48sec. (this happens more often)
When 3 zealots managed to fit in vs greater spire at Step 2, then it dies in 38sec.
Unlike 4 Zealots experiments that resulted in either 38sec or 48sec and nothing in between, 8 Zealots experiment results were more diverse. 34sec was the best record among them.

Depending on the number of Zealots, they take around twice or 3 times more time to kill protected greater spire = about 20-35 sec additional time. As long as you have lings/roaches on your side of the map, it is usually enough time to get back in time. DTs significantly speed up the process, though. This is a little known fact, but not only do DTs have better DPS, but also DTs are smaller than Zealots which make them better when attacking from 1 side. At Step 2, DTs are far more likely to attack greater spire in trio than Zealots which usually work in duo and rarely in trio.

I do this windmill arrangement whenever my ZvP gets into lategame. I am nowhere near pro level, so my opponent is as terrible as myself. They don’t do zealot/DT harass as often as those pros. Even so, I hardly ever lose my greater spire when it does happen because this wall-in buys so much time for my horrible response time. Therefore, from my perspective, I have always thought pro Zerg players are just too lazy(?) to this simple sim city. I don’t know. There might be actually reasons not to do this, but from what I’ve seen, even pros lose greater spire way too easily with no wall-in or failed wall-in with spines.

I actually came up with this idea when I was playing a custom game called phantom mode. When I turtled in my base with 500 supply in 1v3 situation, my greater spire was sniped by DT warp-ins and I couldn’t remax fast enough because of it. Then, I started to do research on careful tech building placements, during which I found this to be very effective even on ladder.

I hope this helped some players. I did as extensive research as I could think of and my time allowed. Feedback/counter argument is much appreciated.