StarCraft II: A Look Back

[Nicol Bolas]

Introduction

So, StarCraft II is out. For those who played the beta, SC2 has been out for over a year now. But SC2 has been in development for much longer than that.

Blizzard gave the Internet rather unprecedented access to SC2 as a game in development. Ever since the initial reveal at the Blizzard World-Wide Invitational in 2007, they have shown SC2 off in various forms over the 3 years before it was finally released. They also released more information in semi-regular posts on Blizzard's SC2 message boards. For those who actively followed the development of SC2 from the very first days public information was available, it was quite an experience to see the game take shape.

With SC2 having been available for some time now, it is worth looking back at some of the ideas Blizzard investigated. Some were retained in their original forms, others were modified and adjusted, while others still were scrapped entirely. Perhaps in looking at what stayed and what went, we can gain some insight into Blizzard's thought processes and how SC2 came into being as it did.

The following information has been culled from a variety of sources. The three races had their own special revelations, complete with a video overview detailing much of the current state of that race. We will be looking at them in the order that they were revealed.

Please note that this information may be inaccurate. All efforts have been made to make this as accurate as possible, but some of the historical records are inconsistent or spotty on certain facts. And of course, this document is based entirely on information that was made public; certainly there was much more that happened behind the scenes than was ever revealed. Also, this history will focus primarily on the gameplay side of SC2's development. While SC2's art evolution would certainly be an interesting topic, that is not the focus of this history.

Also, this is not intended to be a 100% comprehensive history of every known change that happened to every unit. Instead, this history attempts to document the most important changes or those that can give insight into the thought processes and design methadology of Blizzard. Most of the big changes will be touched on, but not every change will be discussed.

Historical Overview

The history of the release of SC2 information itself is rather interesting, and may offer some insight into SC2's development process. The initial reveal at BWWI in 2007 revolved primarily around the Protoss. While a few new Zerg and Terran units and mechanics showed up, the focus was clearly on the Protoss.

2007 saw a great deal of information released about SC2. A second supplementary video for the Protoss was made available, which revealed a number of other units. The fact that almost all of these units disappeared or reverted to older unit forms is telling. It shows that Blizzard clearly wanted to put forth solid ideas at BWWI, rather than more experimental forms and concepts.

Then there was the Terran reveal. And what's interesting to note here is that, if you compare the two reveals, the Terrans changed much more than the Protoss. Units that we now think of as staple Terran units like the Marauder and Medivac were not only not shown in the reveal, they didn't even exist yet.

Another source of information were semi-regular posts from Blizzard's community managers for SC2. These were more likely to update us on more minor changes, those that never made it into major SC2 displays.

In early 2008, we got the major Zerg reveal. This is something best discussed in the Zerg section. At BWWI 08, players first were able to actually use the Zerg. And at BlizzCon 08, we started to see the game really coming together in its final form. Most of the spellcasters had spells that are not entirely unlike the spells they have now, the roster of units was essentially there, etc.

While there were certainly substantive changes between the BlizzCon 08 and release versions, they weren't nearly as significant as the changes between the initial reveal and BlizzCon 08. A few spells were added, removed, or tweaked, and obviously unit stats were changed. But there were no units added or removed from the game (that we know of, of course).

During this time period, the community managers released very little information about SC2, particularly compared to the prior year's releases. Our primary sources of information were the Battle Reports: four internal replays that lead designer Dustin Browder and Matt Cooper recorded commentaries for.

[Nicol Bolas]

En Taro Adun

We will start our look back at the development of SC2 with the first race that was officially revealed to us: the Protoss.

Overall, we see that most of the basic mechanics remained intact. That is, they weren't removed or heavily modified. Warp-In was there and was essentially unchanged from the version we got. The Warp Prism, then called the Phase Prism, had a minor change in the shrinking of the generated field, but ultimately worked exactly as it does now.

The name change of the Phase Prism was interesting and suggests a certain mode of thought from Blizzard. The Photon Cannon was originally called the Phase Cannon, and it had the ability to transform into a mobile form. The mobile form, much like Zerg Crawlers from today, could un-Phase if it was within the range of Psi.

The fact that they used the "Phase" name on two units strongly suggests that Blizzard was trying to make "Phasing" a Protoss thing. Indeed, for a time, High Templar had an ability called "Phase Shift" that would cause a unit to phase out; they could neither attack nor be attacked. There may have been other "Phase" units or abilities that combine well with fields of Psi. Indeed, Warp-In is a big part of that, even though it doesn't use the same nomenclature.

It's interesting to note that quite a few units remained essentially unchanged from the initial. Zealots with Charge and Stalkers with Blink remained throughout the game. The only real change the Immortal suffered was moving from the Gateway/Warpgate to the Robotics Facility. Now, obviously these units changed in stats over time, but the abilities and fundamental nature of these units was not changed.

Now, let's take a detailed look at certain units that changed.

Phoenix: Overload vs. Grav

The initial version of the Phoenix did not have its Graviton Beam ability. The first Phoenix was both AtA and AtG, and it had Overload: an AtA cooldown-based AoE special ability. This AoE ability is really where the "Phoenix" name comes from.

The mythical Phoenix was a bird that incinerated itself, but was reborn afterwards. The Phoenix's Overload caused the unit to shut down for some time after activating it. This doesn't mean much if the Phoenix group wins, but if they lose, you're screwed.

So, why the changes? Well, the Phoenix's AtG attack was taken out in 2008. Looking back, it would be kinda strong to have such a fast unit that could deliver reasonably strong ground attacks. Think about how powerful Phoenix harass can be nowadays, then take away the need to lift units.

As for Overload itself, it seems that it may not have been particularly powerful. While it would be good for Mutalisks, which are rather short ranged, their utility against Terrain air units would be somewhat dubious. That makes the ability pretty one-dimensional.

Graviton Beam makes for a more interesting ability. It can be used with Phoenixes in small numbers to impair certain units, but it can also be used with greater numbers of Phoenixes to directly attack ground targets. And, because the ability is limited, a Protoss player will have to invest fairly heavily in Phoenixes to do lots of damage to ground units with them. This preserves the Phoenix as primarily an AtA unit, but still allows it to be useful when there are no flying units around.

Graviton Beam was initially used on what will become the Sentry (see below). It could have been moved to the Phoenix because it combos much better with a flying unit. Lifting an air unit works much better with a unit that has AtA attacks. Plus, the fact that it flies means that it can more easily flank an opponent, thus being able to lift specific targets.

Rays: Warp vs. Void

The Warp Ray, the original incarnation of the Void Ray, wasn't that much different from its current incarnation. They both fire a beam of continuous damage. They both charge up, dealing more damage the longer they stay focused on a target. But that's where the similarities end.

The Warp Ray had 3 levels of charge, like the Beta-edition Void Ray. But the key difference is that the Warp Ray didn't retain its charge across targets. This is obviously much weaker than the Void Ray we got, so let's examine what happened.

The Warp Ray, conceptually, was designed as a dedicated high Hp unit/building killer. That's what the charging mechanism does. When fired at a high Hp target, it would have time to build its DPS to its maximum level, killing it much faster per-unit-cost than any other unit in the game. When it fires at a low Hp target, it would spend lots of time in low-DPS mode, and therefore be cost-ineffective at killing them.

This also made for some unique interaction with target firing. For normal units, it's not a terrible idea to have them all focused on a single target. While it can lead to overkill situations for units that don't instantly hit, the wasted shots aren't that bad.

With Warp Rays, there is the notion that you can kill something too quickly. That if you have seven WRs, it's often best to split them up on different targets. Because the charge is lost when the unit dies, the best way to deal the most damage is to have WRs fully charged for as long as possible. And that meant splitting targets.

Blizzard, in one of their various forum posts on the game, admitted at some point that Warp Rays were underutilized in their internal testing. And it's not too hard to see why.

First, most non-Protoss units don't have high Hp. Even something like a Siege Tank with 150Hp is not going to be the most cost-effective use of a Warp Ray. You'd have to be attacking truly high Hp units like Thors, Colossi, Ultralisks and the like to be cost-effective. And quite frankly, there aren't that many of those on the field at any one time. Sure, Warp Rays make great building killers, but you don't build units just to kill buildings.

Second, high Hp units have the ability to run away. And the first incarnation of Warp Rays could not follow units while shooting at them; Blizzard didn't implement that mechanic for quite some time after the initial reveal.

The change allowing the Ray to hold its charge temporarily allowed the unit to become much more useful. At the same time, it also broke the intended purpose of the unit. After all, a fully-charged Void Ray is pretty cost-effective at killing anything it can shoot, while the original concept is supposed to be bad at killing low Hp units. This is why its damage was nerfed significantly (the original WR form did a flat 24 damage at full charge), giving it a bias towards armored and massive units.

However, this change came very late in the process. We were only informed of it around the time the Beta was released. While Blizzard was obviously testing it sometime before then, it's clear that it was something relatively new to the build. I think what this shows is that Blizzard probably tried to hold on to the original design concept a little too long. They were very hesitant to do things that made VRs effective against what were not supposed to be their primary targets.

Tempest vs. Carrier

The Tempest was not in the initial reveal, but it was shown by Blizzard sometime between the Protoss reveal and the Terran reveal. Indeed, there were a number of Protoss units that were talked about between these two events that vanished into the aether. The Tempest is the one we know the most about.

The Tempest was a variation on the concept of the Carrier. It used launched Shurikens instead of Intercepters. This is an interesting change, because Shurikens would be melee while Intercepters are ranged. That may sound trivial, but remember: Dark Swarm was still around at this time. Dark Swarm, Guardian Shield, and similar abilities would not affect the Tempest's Shurikens.

But the major difference was that the Tempest had very tough shields. It didn't have a special ability like the Immortal; the Tempest just had a lot of shield Hp. The gimmick was that the shields only blocked GtA attacks. Any flying units would directly attack the Hp of the unit. The Tempest was also much shorter ranged than the Carrier. One of the only videos of them featured them attacking missile turrets, but only from within the turret's attack range (where Carriers would be able to stay well outside of range).

The Phoenix, Warp Ray, and Tempest show a great degree of creativity from Blizzard. They were looking at ways to do things in new and interesting ways. The Phoenix's Overload attack, coupled with AtA and AtG, was a way of combining the Corsair and the Scout into a unit that didn't suck the way the Scout did, but also didn't make mass air units instantly obsolete the way Corsairs did. The Warp Ray's charge mechanic meant that it worked best against high Hp units. And the Tempest was directed more towards ground units that fired back; they would be much more cost-effective than Phoenixes (which still had their AtG attack), since they had more shields per-unit-costs than Phoenixes.

And yet, all of these ideas failed to varying degrees. The Tempest was the first to go. But why did they drop it specifically?

It's not entirely clear. A lot of people online really hated the Shurikens. There were also a lot of people wanting the Carrier back. Blizzard said that one of the reasons for dropping the Tempest in favor of the Carrier was the latter's popularity.

It may also have been that the Tempest's ground-only shields weren't working out. They may have been too vulnerable, especially considering the version of the Vikings they had to face in those days (mass-produced from a Factory, though lacking the 10 range they have now). Considering that, once you take away the ground shield mechanic, Tempests are basically just Carriers with shorter range, you could see why they would just revert to Carriers if the Tempest's mechanic wasn't working.

Colossus vs. Colossus

The Colossus. Like the Phoenix, it didn't get a name change. What changed was the way its attack worked.

The thinking behind the original Colossus's attack was as follows. Units that do lots of damage in a single shot but have a long cooldown are stronger against units with larger hitpoints. This is because they usually waste a lot of damage by overkilling units. A unit that did 144 damage to a Zergling is wasting a good 75% of their damage. Siege Tanks and Reavers gain their strength against low-Hp units because they have AoE.

The Colossus was originally an attempt to have a unit with high damage and a long cooldown attack that would still be effective against low-Hp units, but without resorting to AoE the way that Siege Tanks and Reavers did. It did 144 damage, but in 12-point packets. If the unit died, it would move its beam to another target. This would allow it to be relatively equally effective against high and low-Hp units.

So, how exactly did this unit become a linear-AoE machine, when the whole point of the unit was to not have AoE? Well, probably because the original idea just didn't work.

The Colossus is a pretty high-tech unit. By the time it comes out, low-Hp units will be out by the dozens. Even if the Colossus delivered its 144 damage spread perfectly over Zerglings, it would only kill 4 of them per shot. That's not a lot. A Reaver could kill 12+ tightly packed Zerglings in a single shot (let alone what they could do to Hydralisks), while still being very effective against single targets. So this version of the Colossus was comparatively not exactly cost-effective.

Indeed, this shows that the idea itself was fundamentally unworkable. You could make the Colossus's attack stronger, dealing 24 or 30 attacks in 12-point bundles per salvo. But that comes out to 288-360 damage per attack. This would make it really effective against high Hp units, thus taking away from the Warp/Void Ray.

The fact that the Colossus could be hit by every unit in the game that can attack made it even less cost effective. At least if you lost your Reaver's Shuttle, the Reaver would survive if you dropped it in time (though perhaps not for long, but it might at least get a shot off).

Blizzard changed this much more quickly than the Void Ray change. By the time of the Zerg reveal, less than a year after the Protoss unveiling, they had already changed the Colossus to it's current linear AoE incarnation. They tweaked it a bit since then, visually going from a wide-beam that was surely a placeholder animation to the laser-sweep we have now. And they changed the area a bit. But it's the same concept overall.

It should also be noted that the Colossus is clearly one of those "artist driven" units. That is, someone came up with the concept of what it should look like (Protoss should have a War of the Worlds-style Tripod that burns things), and then design had to figure out a way to make that work. While the cliff-climbing mechanic makes the unit interesting, the fact that every unit could attack it meant that it needed to be more powerful to compensate. If it weren't for the art, they could have removed the unit's height and reduced its effectiveness to compensate.

The Phoenix, Tempest, and Warp Ray were all units conceived of by the designers for a purpose. The Colossus was given a purpose based on how it looked. I'll leave judgments as to which ideas worked out best overall to you.

Mothership: Awesome vs. Arbiter

And speaking of "artist driven" unit design, say hello to the Mothership.

The initial Mothership at the Protoss reveal was a masterpiece of death. With a single spellcast, it could kill any number of air units. It could protect an area for a period of time from all ranged attacks. And it could rain destruction on ground targets at will. The initial demo was rigged with much faster shield and energy regeneration, but it was clear that one of these could ruin someone's day.

The current Mothership... isn't. It's a crappy Arbiter that you can only make one of. That's not to say that it doesn't have its uses, but it's clearly not a unit that sees frequent play.

There are a lot of inherent difficulties with designing any unit that you can only make one of. One of the big ones is that it can't be everywhere at once. You couldn't effectively attack the deathbringer version of the Mothership with anything short of your full army. And if you did, you could expect to lose a lot of it.

Or you could walk around it and just go kill him.

There are other problems, of course. If your army is balanced around having the God-mode unit around, then it will be necessarily weaker without one. So everyone will want to get one. And if your army is able to stand up without the unique unit around, then building it will act as a force multiplier. It's hard enough to find the right balance for units that you can build lots of. But for a binary unit, one that is either present or absent, it makes a hard problem that much moreso.

This is a vast simplification of a complex topic of course.

Blizzard apparently choose to balance the game around not having the Mothership, then reduced the Mothership's powers to the point where it isn't a huge force multiplier. Of course, because it's not a force multiplier, people generally don't bother. It's not integral to their play, so they don't make them.

Blizzard did try a lot of things with the Mothership over the course of development. They gave it powers like transferring energy to nearby units, passively allowing it to be a mobile Warp-in point, and they even took away its unique status to allowing more than one to be built. They eventually settled on the current slate of powers: a poor-mans Arbiter.

From Relic to Sentry

There was once a unit called the Star Relic. Cool name, btw. But there isn't much information about what this exactly was. It wasn't shown off in the initial reveal, and I don't think we even have pictures of it. We do know that it was a unit that was at a comparable place in the tech tree to the Arbiter. And we know it had some abilities that were similar to the Arbiter, though it also had Hallucinate at one point.

The Star Relic does live on, however. Blizzard experimented with a Protoss unit called the Stasis Orb after cutting the Star Relic. The Orb was a ground unit, much lower in tech, and it had an attack that slowed units down (sound familiar, Terran players?). This was quickly discarded in favor of the Nullifier.

The Nullifier was one of the first early-game casters that Blizzard started talking about. It had an ability called Force Field, which is essentially unchanged from the modern Sentry. It also had Null Void, which was an AoE ability that targeted an area; units in that area could not cast spells or activate many kinds of abilities. It's not clear whether this could affect abilities like Siege Mode.

Later, the Null Void ability gained the power to reveal cloaked/burrowed units in the area of effect, in addition to shutting down spellcasting. Much like EMP does now.

Null Void seemed like a powerful ability. But perhaps it was a bit too powerful for such an early-game caster. That may be why it was removed. Mass Null Void, launched the way Protoss players spam Force Fields nowadays, would be exceedingly annoying to deal with. However, it does make me lament the lack of a mid-game Protoss caster. Perhaps something that comes out of the Stargate. It wouldn't require the Fleet Beacon, so you could make them right away. And it would come with Null Void standard. But it would have other researchables from the Beacon.

Null Void was eventually dropped in favor of Hallucination, which again remains essentially unchanged. For a time, Nullifiers also had Anti-Gravity, what would eventually become Graviton Beam for the Phoenix. That was dropped at BlizzCon 08 in favor of Molecular Disruption. AKA: Chain Lightning.

In Battle Report 3, we found that the Nullifier had been renamed the Disruptor. By the Beta, it had taken on the now-familiar name Sentry, as well as having its the chain lightning spell replaced with Guardian Shield. This obviously fit more into the "sentry" mode, since it doesn't involve attacking things.

DOA: Soul Hunter

This was a unit that was pretty much universally reviled. It's not often you see the internet truly united like this. We at least got pictures of it, but that's where a lot of the hate comes from: Zealots on surfboards.

The Soul Hunter's gimmick was that, the more units it killed, the more damage it did. The specifics of this power weren't known, but that was the general idea. People didn't like the idea of Protoss collecting "souls" and being empowered by them; that sounds like WarCraft stuff. And nothing gets StarCraft players in a bigger tizzy than introducing anything that seems even remotely WarCraft-like into the game.

What's interesting is that the modern Void Ray is basically that mechanic: it gets better the longer it is in combat. Granted, it does so by firing and specifically not killing for a time, but the principle is the same.

[Nicol Bolas]

No Matter the Cost

The Terrans were the second SC2 race to be revealed, a few months before BlizzCon 07. A few Terran units were shown at the initial SC2 reveal, but it wasn't until later before we got a real look at the race.

This reveal introduced a number of things that survived through today. We saw the Reactor/Tech Labs, which were mostly unchanged from what was released. We saw the Orbital Command and Planetary Fortress; while the OC was just a ComScan machine at that point, the PF remained basically the same.

Even so, it's clear that the Terrans went through a few more modifications from their reveal than the Protoss. While there were several Protoss units that proceeded essentially untouched from the reveal through to the final release, there were fewer Terran units that did so. And those that did were legacy units like the Marine and Siege Tank.

The Medivac is an interesting example. Obviously, it's a combination DropShip and Medic; that's its purpose. What is interesting is the fusion itself. You will see that with the Terrans, the general policy with changing things was to move abilities and concepts around. And specifically, to not just drop stuff. That's not to say that abilities weren't cut, but its clear that Blizzard spent a lot of time with the Terrans in finding places where things worked best.

Barracks and Factory

It's really hard to talk about units like the Hellion, Viking, and other units without talking implicitly about the others. They all interacted with one another in the year after the Terran reveal.

At the initial Terran reveal, we saw Vikings. They were produced by the Factory. Indeed, they were the base Factory unit, needing neither a Tech Lab nor an Armory. Their flight mode required research from a Tech Lab, and that research needed a Starport. So they didn't make flying units lower tier per-se.

There was also the Cobra. This is a unit that is not unlike the Diamondback from the SC2 campaign (get it? Cobra? Diamond-back? They're both snakes). A hovering, reasonably fast unit that shot stuff. It's claim to fame was the ability to shoot while moving. It took the Goliath spot in the Factory, and naturally, it had the ability to shoot air units.

Sometime later, the Cobra inherited the Protoss Stasis Orb's slowing ability. That is, its attack slowed units down. You can probably see where this is going.

A bit later, a number of things happened. The Firebat was reintroduced. However, Blizzard wanted to try something: have the Firebat be a Factory-produced unit. The Cobra was cut, but this left the Viking in a kind of limbo. So they moved it to the Starport. Essentially, they changed it from a ground unit that could fly into an air unit that could land.

Later still, just before the Zerg reveal, we started to get something more in the vein of what we see today. The Firebat and the final phase of the Cobra were decomposed and adjusted into two new units: the Marauder and the Jackal.

The Marauder uses a reskin of the Firebat's model. This suggests that the Firebats they were testing were somewhat beefier than the SC1 Firebats, which is reflected in the SC2 campaign Firebat. The Marauder kept that beefiness, but dropped the melee-style AoE in favor of a traditional ranged attack. It also took the Cobra/Stasis Orb's slowing ability, where it remains through today. Lastly, it moved back to the Barracks.

The Jackal is identical to what we know as the Hellion; though it went through a few model and name changes, the Jackal is pretty much what the Hellion is. It fires a relatively long-ranged linear AoE attack. The Infernal Pre-Ignighter upgrade came much later. For a time, the Jackal/Hellion had an attack speed upgrade instead of the blue flames.

Also, due to changes in the Thor around this time, Blizzard moved the Viking back to the Factory for a time. There were also some reports that Vikings had a GtA attack in their ground form at this stage. The nature of this attack was unknown, and the sources are unclear to the point where I'm not even sure if the report was accurate. However, it is known that the Thor also temporarily lost their GtA attack around this time, which explains this move.

Obviously, Vikings were later moved back to the Starport and lost the GtA attack.

What is most interesting to me in this series of changes is how Blizzard was thinking about infantry. The SC1 Firebat was clearly about killing stuff. It had slightly more Hp than a Marine, but it's main purpose was burning down small units (since its attack was Concussive).

In SC1, everything that the Barracks produced had very low Hp. While the Barracks was a cheap structure that produced cheap units, this also meant that any significant AoE attacks instantly nullified all Barracks play. The mere threat of a Reaver in SC1 made the use of any Barracks units in TvP useless outside of rushes. If you were planning any kind of macro game in TvP, you went Mech. The same goes for TvT; Siege Tanks en-masse simply kill infantry too quickly and efficiently to make them effective.

Note that there was no "transitioning" into Mech play. You built a Barracks and then a Factory immediately thereafter. No Academy, no Engineering Bay (save for Missile Turrets), no Bunkers, nada. You only built a few Marines to survive until your first Siege Tank came out to stop the inevitable Zealot/Dragoon harassment of your wall-in.

Looking at the SC2 Firebat, larger in size and higher Hp, it's clear that Blizzard was looking at ways to allow infantry units to not be made completely worthless by any form of AoE. Particularly since they gave Zerg Banelings. Lurkers have AoE, but they're static; you have to walk into them for them to affect you. Banelings can come get you.

The Marauder is essentially that. An infantry unit that doesn't immediately die to AoE. Unlike the Firebat, it has an actual ranged attack. It slows targets down, thus allowing Marine's high damage over time to kick in. They work as meatshields for Marines, while still being able to put the hurt on other units.

Though perhaps giving them Stim was a bit much. There was a time when Marauders didn't have that.

I would say that the unit that suffered the most from these changes was the Viking. The original Viking was meant to be evocative of Goliaths. However, in order to do their fearsome anti-air attacks, they would have to become air units themselves. This also allowed them to become their own Dropships and execute drops on their own, giving them another purpose. Vikings were ground units that could become air units.

The current Viking is basically a super-Wraith that gets a stronger ground attack, but must actually become a ground unit to utilize it. Because they're higher tech, you can't just build some; you have to want them. And ground-based Vikings could easily have taken on much of the role of Marauders, acting as meatshields for infantry. Sure, you would need a Factory to make them, but one or two Factories with Reactors would allow you to make plenty. Plus, investing in a few Factories could make it easier to slowly transition into Mech play if the need arises.

Siege Tanks vs. The World

Blizzard very clearly made the decision early on in SC2's development that certain units from SC1 were sacrosanct. Untouchable. They could alter basic stats, but these units would certainly make it into the final game.

The Siege Tank was just as clearly one of these. It debuted in the Protoss reveal, mainly as a way to show off how Immortals could kill them. Indeed, the Immortal's hardened shield seemed tailor-made for killing tanks.

This decision had a number of consequences. The biggest were on the Banshee and the Thor.

The original Banshee was an AtG AoE attacker. It fired a swarm of missiles at ground targets. Basically, it was a flying Siege Tank that could cloak. It had mobility and AoE, but not the single-shot stopping power and strong single-target damage that Siege Tanks had.

That part was reserved for the Thor. The original Thor was constructed by SCVs (not transportable by DropShips). This form of the Thor had a strong single-target attack that could be used on ground and flying targets alike. That is, no missile GtA attack. The Thor also had loads of Hp. Added on to this was Barrage Mode. This visually is similar to the current Thor's 250mm Strike Cannon, but it instead of being a single-target damage attack, it was a channeling AoE attack. Basically, it does a lot of AoE at an area.

The Thor was a different take on a siege unit, much like the Immortal. Most siege units work by being able to stand out of a building's range and kill it that way. The Thor would have to take fire from its targets in order to attack, but it had more than enough Hp to do that as well as Barrage its targets to pieces.

However, unlike Siege Mode, you can't Barrage forever; it was a channeling, energy-based ability. So if your enemy could survive the initial pounding, they could break you. Thors were also vulnerable to fast units, since they were the one SC2 unit that actually had a turning speed. You could micro against them with fast units, staying ahead of their turning speed, and the Thor would be unable to shoot back.

These units are basically incompatible with Siege Tanks. Either STs would be more cost efficient than them at those tasks, or those units would be. So one set of units or the other would be used preferentially. That meant that either Siege Tanks had to go, or those units had to be changed. And since Blizzard decided that Siege Tanks were sacrosanct...

To be perfectly honest, I would have rather seen Siege Tanks go. Taking the ST powers and spreading it over two other units could have created some interesting dynamics. Then again, considering how accessible Banshees are, maybe it would be a bad idea to have them be AoE units. Of course, they could have simply added a post-Starport building that allowed Banshee production.

The Thor had things much rougher than the Banshee. When the Viking moved to the Starport and the Cobra was cut, Blizzard found that they needed a decent GtA unit at the Factory tech level. So they refitted the Thor for this purpose, giving it an AoE GtA attack.

Because Barrage Mode overlapped with Siege Tanks and would likely have gone unused, Blizzard removed it in favor of something called Mechanical Rebirth. The idea here is that, when you killed a Thor, it would turn into wreckage. It would still be on the battlefield, and still be targetable. The wreckage would have a certain number of Hp; once those were exhausted, the Thor was fully destroyed.

Wreckage could be repaired by SCV, causing the Thor to come back. However, the Wreckage could do this by itself as well, costing a fraction of the build-price of a Thor. The idea with this is to allow a Thor to remain a priority target even when it's not actually able to deal damage. Thus the Thor can effectively have more hit points without causing it to be truly longer lived.

Why was it replaced with 250mm Strike Cannons? No idea. Maybe it was too strong? Or just not particularly important.

From Nomad to Raven

The unit we know of as the Raven started its life as the Nomad, a Science Vessel replacement. The original idea behind this unit was to be analogous to an SCV. It was a unit that built things, and initially it could even repair flying units. The first art for the unit was similar to this concept; it looked like a flying construction apparatus.

The auto-turret was the first spell we learned of for the Nomad. This obviously was retained through release.

The next ability we learned about was a cloaked mine drone. The idea was that the drone would place cloaked mines in an area. This was eventually replaced with just building SC1-style Spider Mines. If Ravens still had that power, I bet they'd see more use now (unless it required research).

At BlizzCon 08, the Nomad was renamed the Nighthawk, and it was given the model it currently has. Sometime after that, it was renamed Raven. I have no idea why they picked Raven over Nighthawk; I much prefer the latter myself. The Nighthawk lacked the Nomad's repair abilities.

Also at BlizzCon 08, we saw the Targeting Drone. This allowed the user to select a particular target, and all attacks against that target got a 50% damage buff. This was probably dropped due to not being nearly useful enough. Especially with the later Hunter-Seeker Missile, which at least did AoE damage.

The Nighthawk gained the Hunter-Seeker Missile (later renamed Seeker Missile) sometime later. Point-Defense Drones came later still.

Reapers and Explosives

The Reaper was the first new unit we saw from the Terrans in SC2. They were featured in the initial Protoss reveal, as a harassment unit that killed Immortals and could jump cliffs. The Reaper only underwent one major change in SC2's development: D8 charges.

In the Terran reveal, D8 Charge was a cooldown-based ability. It caused the Reaper to throw a timed explosive on a selected location. After a short duration, it would explode.

This was eventually replaced by a special anti-building attack. Why? I have no idea.

The D8 Charges were a theoretically cool ability. Reapers could force enemy targets to temporarily vacate an area by essentially mining the area. Of course, D8 Charges don't discriminate, so you couldn't move through and claim the area yourself. They also allowed Reapers to be able to quickly take out buildings (unless they're flying buildings). Obviously that part was retained.

The other thing was that, at one point, D8 Charges were targetable. Thus, an enemy could negate this effect. Perhaps that made them essentially useless. But it's clear from Battle Report 2 that they later became untargetable. So this couldn't be the reason for the change.

It's also interesting to note that the D8 Charge change seems to be relatively recent. The last of the Battle Reports, released in late 2009, shows that Reapers still had D8 Charges as a researched ability, rather than as a special attack. They also had Stim.

Another change was how Reapers were produced. In the initial Terran reveal, Reapers were produced, not from a Barracks, but directly from a building called the Merc Haven. The idea was that you could build Reapers in clusters, rather than one at a time. This meant that you could fairly quickly gets 3 or 4 Reapers, but building 12 would take some time.

Giving Reapers their own production building was a nifty idea, but I can see why they scrapped it. It could easily be over-complicated. And it didn't fit very well with the standard Terran production scheme.

Sensation

Just as with the Protoss notion of "Phasing," it is clear that the Terrans were to be given a dimension involving "sensing" other units. This was an extension of the whole ComSat thing from SC1.

The Sensor Tower is a part of that. Originally, the Sensor Tower only allowed nearby Missile Turrets to detect; the Turrets couldn't do that by default. This was obviously a way to make cloaking more effective against the Terrans.

A Sensor Tower could be upgraded into a Radar Tower. In addition to allowing Turrets to detect, the Radar Tower does what the Sensor Tower does now: detect the presence of units in the Fog of War.

The old-style Sensor Tower/Radar Tower was probably taken out for two reasons. One, detecting things in the Fog of War isn't worth that much money (building plus upgrade). And two, needing Sensor Towers to have static detection on top of the cost of Missile Turrets was probably too much. Ironically, it would have had the opposite effect: it would have made the Terrans more vulnerable to cloaking. Kill the Sensor Tower, and it doesn't matter how many Missile Turrets they have.

Ghosts even had an ability for a time to sense the presence of units with energy up to a range of 30. I'm not sure how good of an idea that is, and Blizzard may have agreed, as it was yanked out of the build fairly quickly.

Drop Pods

Speaking of Ghosts, they once had another ability that factored into a scheme that Blizzard was looking to exploit. Namely, lots of mobility. Protoss Warp-In allowed them to produce units in arbitrary locations. And while Blizzard wasn't going to give every race that particular kind of mobility, they did investigate doing something somewhat similar for Terrans.

Enter Drop Pods. These were produced like Nukes: directly from the Ghost Academy (or whatever they called it back then). Ghosts could call down a pre-constructed Drop Pod, and it would create 5 Marines at the target location. The Drop Pod model was later reused for MULEs.

Later on, Drop Pods were changed to be able to load any infantry into them, rather than simply creating Marines from whole cloth. Imagine how scary a double Drop Pod bristling with Marauders would be in your main. Which might explain why they took it out.

Would Drop Pods have made for a good mechanic? Well, with Medivacs being a virtual necessity in Infantry-based builds just for their healing abilities, the utility of Drop Pods may simply have waned. The main advantage of Drop Pods over regular drops was ensuring that, so long as the Ghost survived, the Marines would actually show up on the field of battle. Probably not really worth it.

Weapon Refit

That's an odd name for the Yamato Cannon upgrade for BCs, isn't it? That's because, once upon a time, Battlecruisers had many different possible powers.

The way it used to work was simple. You researched one upgrade at what eventually became known as the Fusion Core. This would give each BC the ability to permanently pick a special power that they wanted. You clicked on each individual BC and gave it a refit. The refit time was pretty short, and thereafter, that BC was stuck using that power.

In the beginning, there were two powers: Yamato and Plasma Torpedo. The latter was an AtG AoE attack, much like Psi Storm only stronger. It didn't have much range on it, so the BC would have to expose itself to fire to use it.

The difference of course is that Psi Storm comes from an 80Hp ground unit, while BCs are 500Hp flying units. And are repairable. You can flank someone attempting to use Psi Storms in an attempt to kill their HTs before they can cast it, while you can't really do that with BCs. Neural Parasite wasn't around at this point, but even that is a Zerg-only ability.

So Plasma Torpedo was scrapped in favor of Missile Barrage: an AoE, AtA missile attack. And later, they added a third option: a self-only Defensive Matrix.

Personally, I liked the idea of BCs having multiple options that they choose from, though I was never particularly happy with the powers they choose. It's hard to give high-Hp, high-cost units like BCs powerful spells, for similar reasons as the Mothership. Defensive Matrix might have been somewhat nice as a way to forestall death, but getting the quantity of extra hitpoints right would be difficult.

DOA: Predator

At BlizzCon 07, there was a flying unit called the Predator. Much like the Star Relic, very little is known of it. Not even pictures exist.

What is known is that it was an AtA fighter. It had an AoE AtA attack; indeed, it was the only AtA unit that we know of that ever had an actual AoE attack (the Phoenix Overload was an AoE special ability). But it's main claim to fame was that it could enter Intercept mode.

In this mode, projectile-based attacks made nearby would be intercepted. So yes, this was the precursor to the Nighthawk/Raven's Point-Defense Drone. It's not known if it was an energy-limited ability, time-limited, or if there were any limitations on it at all.

Once the Viking became a flying unit that can land (rather than a ground unit that can take off), the Predator lost much of its reason for existence. It was not seen since BlizzCon 07.

[Nicol Bolas]

Eradicate and Evolve

The Zerg were revealed in early 2008. And their reveal was quite revealing indeed.

The Protoss reveal was very formal. It was at a major event, and Blizzard clearly wanted to impress. And impress they did. They showed off big units, impressive abilities, and so forth. The Protoss reveal video was captured and posted online for download, with voiceover by lead designer Dustin Browder explaining all of the new stuff.

The Terran reveal happened outside of a major event. It didn't have as much fanfare. Even so, the video was released with Browder's narration explaining the new mechanics. In both cases, the videos represented all of the features that they were willing to talk about for that race at that time.

The Zerg reveal was much more clumsy and haphazard. The demo video had no narration with it (note: if you remember differently, you're remembering the BWWI 08 video, not the initial Zerg reveal that happened before then). It was just a series of clips of units doing things.

What was worse was the textual information that came with it. It described things that weren't shown in the video (mainly dealing with the Queen), thus showing that the video was incomplete. The big problem was that the information didn't seem self-consistent. It suggested that the Zerg had 4 kinds of defensive structures, which doesn't really make sense.

The Protoss and Terran reveals really felt like polished presentations. In both cases, there was hidden information, units and concepts that were still in tumtuous development. Sure, the whole game was subject to change, but they were showing things that they were at least somewhat confident were decent ideas, even if they didn't make it to release.

The Zerg reveal felt like someone took some random footage of a random build of the game and threw it out the door. My theory on this is that Blizzard was still operating under the premise that SC2 would be released in 2008 at that point. So they were making a big push to get things done; a polished demonstration would be taking time away from the task of, you know, shipping the game.

Despite the haphazard nature of the release, almost all of the units shown in the demo survived. Furthermore, there were no known extra Zerg units in development: Blizzard had already boiled the Zerg line up down to these particular units.

That's not to say that the Zerg didn't undergo any major changes, of course. There are several units that are barely recognizable from their former incarnations.

Upgrades

In the Zerg reveal, upgrades worked very differently from other races. Rather than having +1 upgrades for melee, ranged, armor, air attack, and air armor, each individual Zerg unit had 3 upgrades. Also, those other upgrades that Zerg units get, like Zergling speed? They were also folded into the individual unit upgrades. So you upgraded Zerglings Level 1, and all your Zerglings got faster. Along with +1 attack and +1 armor. If you made it to Zerglings Level 3, you also got the Adrenal Glands attack speed boost.

This change has such potential for being utterly broken. Obviously, it depends on how much these upgrades cost. But at the same time, there was a big weakness. When you upgrade +1 ground attacks as Protoss, all your ground units benefit. Zerglings Level 1 might give your Zerglings +1/+1 along with speed, but it does nothing for Banelings. Or Ultralisks. So there is an inherent downside.

The main idea with the Zerg is that, due to the centralized production mechanic, you only need one building and you have access to a unit with your full production capacity. This means that switching to units is about as painless as it can possibly be (not that it isn't without pain). This encourages being able to vary your unit composition.

This individual unit upgrade idea seems to work against that. Zergling Level 1 means nothing to Banelings; they have their own upgrade stack. So even if you decide you need some Banelings, you have to start over with their upgrades. This makes tech switching more expensive. But at the same time, it means that Zerg units could cost less or be stronger, since some of their cost would be eaten up by having to upgrade them individually. Maybe Hydralisks wouldn't have to cost 100/50 if you couldn't upgrade them until you built a Hydralisk Den.

High tech units would probably be the biggest problem. Ultralisks, for example, having to start at +0/+0 would have to be made stronger to compensate. But then, what would happen if you got them up to +3/+3?

I can see why they cut this. This is one of those ideas that you understand intuitively is probably broken, but it would have been great if they could have made it work.

Her Royal Highness

The Queen is probably the best example of a unit that is virtually unrecognizable from the modern perspective.

The Queen at the time of the Zerg reveal was a unique unit; you could only have one of them at a time. When this was revealed, people immediately started suggesting that she was a hero unit, particularly since she got upgrades at Lair and Hive levels. And as previously stated, anything that even slightly resembled anything from WarCraft was attacked by the community.

The truth is that the original Queen was an anti-hero unit. She's about as unheroic as it could get.

The idea behind the Queen was very simple: the Zerg need larva to make units. But Zerg also use larva to make buildings, by using up a drone. While Protoss and Terrans get their workers back, the Zerg lose theirs completely. And while that's fine overall, it mean that the cost of base defense for Zerg is substantially higher. It has more economic impact than simply losing a few minerals worth of mining time.

The Queen was in part a way to fix that. Drones didn't build any base defenses or creep-expanding structures. Instead, the Queen built those. Now, that didn't mean that these buildings didn't cost money; they still did. But what it did mean was that they didn't cost drones or precious larva.

The Queen was a very defensive unit on top of that. It had the restriction on its creep movement speed. And all of its spells only really worked within a Zerg base.

The Queen had Deep Tunnel, a teleportation ability that worked exactly like the Beta Mothership's ability to teleport to any Protoss structure. It had Toxic Creep, which allowed it to cause a patch of Creep to damage units on it. It could cause Zerg buildings to regenerate health faster with Regeneration. And it could cause Zerg buildings to become mini-turrets that attack nearby units with Swarm Infestation.

Not exactly a palette of powers that are useful in the field.

In order to gain those powers, the Queen needed to be upgraded. She upgraded with the Lair and Hive, with each upgrade providing her with an additional power. Deep Tunnel was a Lair-level power. If the Queen was killed, she could be rebuilt at the previous level of power.

The possibility of losing the Queen is probably why most of these changes didn't stick. If something came in and killed the Queen (not easy in those early builds, since she started with Burrow), that meant that no more Zerg defensive buildings could be constructed until she returned.

The first thing to go was using her to construct defensive buildings. And the next was her unique status, along with most of her powers. At BlizzCon 08, the first build of the game we saw with a non-unique Queen, she pretty much had the suite of powers she has now. More or less.

I had a great deal of affection for the original unique Queen. She would have made for some interesting play mechanics.

Defense

The defensive structures available to the Zerg at the time of the initial unveiling were... confused. So confused that I think someone at Blizzard might have simply copied stuff from two separate builds. Or that Blizzard was transitioning the Zerg from one thing to another and the Zerg reveal got caught in the middle of some kind of horrible Frankenstein's Build. None of this was featured in the demo video, but they were talked about in the documentation release.

Sunkens and Spores were still around. They weren't crawlers yet, but you'd think that they would cover the Zerg's defensive needs.

There were also Creep Tumors. Laid by the Queen, Creep Tumors did not self-replicate. Instead, they could be upgraded into Shriekers. These could detect (maybe. It's not entirely clear), but they also gave added range to Swarm Clutches.

What are Swarm Clutches? They're another kind of defensive structure laid by the Queen. They were an egg that hatched when enemies approached within their range (or the range of an associated Shrieker). They could attack both air and ground.

It's not known if the egg was effectively expended if they were hatched; we never actually saw a build with this stuff in there. Indeed, if the Clutches were expended, or had some number of attacks they could make before running out of ammo, then having two kinds of defensive structures makes sense. You use the Sunkens/Spores if you think that the enemy is going to attack a location repeatedly, but you can use the (presumably) cheaper Clutches in locations where they may not. Similarly, if a Zerg player is relying on Clutches to defend, you can try to tank all of their Clutch-based fire to power through their defenses.

I think it would have made for an interesting dynamic with defensive structures. Especially with Shriekers around with their range enhancing abilities. But I'm not Blizzard, and I never got to play a build with this stuff in it.

Roach vs. Hydralisk

Roaches did not have the best introduction. They weren't featured in the initial reveal video, but they were talked about in the textual information.

The original concept for the Roach was creative. They wanted to give the Zerg a unit that could absorb lots of damage, but the Zerg are supposed to be all about having lots of low-Hp units. So they made its tanking abilities based on fast regeneration.

The Roach then proceeded to go through a lot of incarnations. There were versions of the Roach that were Tier 1 with relatively low Hp, but strong regeneration. There were versions of the Roach that were Tier 2, with more Hp and less regeneration. Then came versions where they had decent regeneration above ground, but very fast burrowed regeneration. The latter part is how they came to the current form of the Roach, with its burrowed movement. Burrow-move synergises well with enhanced regen while burrowed.

All of these changes affected the Hydralisk. In order to make room for the Roach, the Hydralisk had to change into something else. When the Roach was Tier 1, the Hydralisk had to take on more of an anti-air role. When the Roach was Tier 2, the Hydralisk needed to be more of a generalist ranged unit, with Roaches primarily used to absorb damage.

The Roach is a lot like the Colossus: an idea that just failed. It was supposed to be a Zerg-style unit that could absorb damage. But it turned into, let's face facts, a Protoss unit in a Zerg skin. The odd part is that, unlike the Colossus, the Roach wasn't an artist-driven unit. The reason it survived was because Blizzard kept trying to make it work.

They moved it to different Tiers. They changed how much it regenerated. They gave it burrowed regeneration. They gave it burrow move. They kept trying to make an unworkable concept work, until their successive changes led to something that was antithetical to the original concept.

Nydus Worm

The Nydus Worm is one of those things that it is very unclear about how it originally worked. We know from the initial Protoss reveal that this form of the Nydus Worm unloaded multiple units at a time. Outside of that, it becomes less clear.

There are indications that, at the time of the Zerg reveal, the Nydus Worm was a unit. A burrowed ground unit that could move anywhere. When on solid ground, it could transform into a Nydus entrance, at which point it acts more or less like what we have now.

Blizzard scrapped this idea, and they may have done so for several reasons. First, there are visual concerns. What exactly does a burrowed unit that's flying through empty space look like? Does it just look like a flying unit? And how exactly do you burrow through empty space, anyway?

But there are also gameplay concerns. Because of this form of Nydus, there was no need to have Overlords carrying units. So they didn't; Nydus Worms were the Zerg transport mechanism. Given that, how do you deal with a ground unit that is still technically on the ground when it is in places that no other ground unit can go? Vikings can't shoot them; they're not flying, and a Viking can't drop down over empty space. Only AtG attacks can hit them, and that's only if they have detection. Again, there's that whole confounding notion of burrowing through empty space.

By BWWI 08, the Nydus Worm was somewhat more recognizable. They were built from the Nydus Network, and they could be placed on the Creep. Thanks to Overlord's being able to drop Creep, this wasn't a huge limitation of their use. Of course, since Nydus Worms were limited in their use, Overlords had to be able to transport units again.

At BlizzCon 08, Blizzard decided to try a different tactic. Once you built a Nydus Network, Overseers would be able to deploy Nydus Worms. This meant that your Overlords didn't have to expose themselves to fire by dropping Creep, but it also meant that you needed to use Overseers to do Nydus play.

The solution they shipped the game with was to be able to spawn Nydus's anywhere that the Zerg had vision. It should be noted that, in order to make this workable, they had to give Nydus's an incredibly long spawn delay. The earlier versions were fairly quick to pop up, while the shipped version takes long enough that just a few workers can slaughter them before they pop.

Infestor

The initial Zerg reveal for the Infestor was clearly a unit that was in transition. It had burrowed movement and the ability to infest buildings, causing them to produce a number of Infested Terrans. It's not known exactly how this worked on Protoss or Zerg buildings. That is, did Pylons start making Infested Terrans or something else? Could a Creep Tumor be infested to make Infested Terrans?

Other than these powers, the Infestor was basically a Defiler. It had Dark Swarm and Disease, which was basically Irradiate.

It wasn't until BlizzCon 08 that the Infestor came into the form we know today. It lost everything except burrowed movement, and gained essentially the powers that we know it for. It could create 5 Infested Terrans. It had Neural Parasite, which was not a channeling ability at the time. And it had Fungal Growth. A few of these abilities had some minor changes, but that's about it.

What this really shows is that Blizzard had gotten much better at designing units over SC2's development. They were able to basically scrap a unit's spell list and give it an entire new suite of powers. Ones that worked reasonably well overall.

Corruptor

Ahh, the Corruptor. It's easy to see that the Zerg counterpart to Protoss "Phasing" and Terran "Sensing" was infestation/corruption. The idea here was to, in some way, use the enemy's buildings or units against them. And it's not a surprise to see that this, like the others, mostly failed, only giving rise to the Infestor in the end.

The original idea behind the Corruptor (well, the first idea we saw. The original original Corruptor was a ground unit) was to have an AtA unit that could be stronger against masses of air units without resorting to AoE. When a Corruptor killed a unit, it would turn into a corrupted unit. This corrupted unit would fire out attacks against other enemy units. Thus, the more units the Corruptors kill, the stronger the group gets.

Well, unless the enemies run away. Since the corrupted units are frozen in place. And flying units aren't bound by terrain. I don't know if Blizzard really thought this plan through...

That's probably being unnecessarily harsh to the ability. If you need the air units to vacate an area, so your Mutalisks can come in and dispense death from above, then it's fine. Even so, this is not exactly the most common occurrence.

The tech position of the Corruptor was moved around a lot as well. In the initial reveal, it was actually at the Lair. That is, you needed only a Lair for Corruptors, so they were readily available. Later, they were moved to the Infestation Pit, which tied into the whole infestation/corruption thing. Eventually, Blizzard gave up and just put it in the most obvious place: the Spire.

In the Beta, the Corruptor was given the power to shut down certain buildings. This synergized at least somewhat with the Corruptor, in that you could use it on static defenses. Blizzard decided to move that over to the Overseer (with a nerf in that it doesn't stop static defenses). And they gave the Corruptor its current ability, which at best makes it more useful against the kinds of targets it was already useful against.

Compare any incarnation of the Corruption ability to Graviton Beam. GB makes Phoenixes very versatile units. No version of the Corruption ability did. At best, it acts as a force-multiplier: making Corruptors stronger against their preferred targets.

MIA: Lurker

The Lurker was the last SC2 unit to be removed from the game (that we know of, of course). It's anomalous in this regard because it was removed relatively recently. When exactly it was taken out is not entirely clear. We know it was in the game at BlizzCon 08, and we know it wasn't in the game at the SC2 Beta. So it vanished sometime between those two events. However, mention was made of an improved model for Lurkers during this time, so there was still at least some intent to keep them around. So it's probably safe to say that the Lurker was removed relatively close to the Beta.

What happened? Well, Blizzard has maintained that the Lurker was cut due to overlap with the Baneling. This doesn't quite pass the smell test. Banelings and Lurkers were both in the game since the initial Protoss reveal in 2007; it could not possibly have taken Blizzard 2+ years to realize that they overlapped.

Part of the issue with the Lurker is that it was associated with the Hydralisk. So every time they moved the Hydralisk/Roach around, they had to move the Lurker with it. A Tier 2 Hydralisk must mean Tier 3 Lurkers. In theory at least; there's no actual reason for that, but that's how Blizzard seemed to work with it.

By that point in a game, detection is pretty readily available. While Lurkers aren't completely dependent on being undetectable, that is a big part of how they work. Blizzard seemed to realize this, so they gave Lurkers a range upgrade that gave them range 9. Even so, being that high tech makes getting them very difficult. Lurkers, even with 9 range, wouldn't have as big an impact as Ultralisks or Brood Lords.

The other big problem is that there is no Dark Swarm in SC2. And while Lurkers aren't dependent on Dark Swarm, it really helps them out. Ranged units can't shoot them, while Lurkers can shoot back just fine. They would work reasonably well with Fungal Growth, but not nearly as well as with Dark Swarm.

The sad thing is that, as the Roach evolved into its current state, the Lurker could easily have been made into a Tier 2 Roach-morph instead of a Hydralisk one. The shipment form of Roaches gain strength from being burrowed, as do Lurkers. It makes sense thematically and from a gameplay perspective.

[Nicol Bolas]

Macro

Sometime in early to mid 2008, Blizzard came to a realization about StarCraft II. They realized that in modernizing SC2's interface, they had also reduced SC2's mechanical complexity. I'm pretty sure they knew that before then, but it took until then to realize that the reduction was not a positive.

Rather than return the interface to 1998, Blizzard decided to use this as an opportunity to add mechanical complexity ways that didn't make the interface feel like something that was made in the Paleozoic era. Enter the Macro Mechanics.

Extinction: Gas Mechanics

Their first attempts at macro mechanics were... kinda sad to be honest. They first started playing with gas geysers.

Version 1.0 of this mechanic was shown at BWWI 08. There, gas geysers provided a relatively small quantity of gas, about 600 units. Workers still gathered depleted gas. However, you could spend 100 minerals to add another 600 gas to the geyser. This process took about 45 seconds or so, during which time geysers were inactive: they couldn't be mined from at all. There was probably a limit on the number of times you could do this, but it's not known what exactly this was.

This was also the introduction of the double-geysers. And that is the only remnant of the gas mechanic experiment that survived.

Version 2.0 was shown off at BlizzCon 08. They did away with the whole paying for gas thing. Instead, after pulling 400 gas from a geyser, it simply shut down for about 45 seconds. Depleted mining was also stopped.

In both cases, the "macro" was about putting your workers to use. During the 45 seconds the geyser spends non-functional, a good player would be able to put those workers to use. So it was about going back to the base, putting workers back on minerals, and then remembering to put them back on the gas after the geyser reactivates.

What we see with this is the most basic idea of a macro mechanic: something that makes you go do something. No more thought was really put into it except for that. This was an obvious and artificial way to make players come back to their base to poke and stuff.

Of course, the fact that workers mine so efficiently in SC2, such that over-saturation of workers on minerals isn't very useful, means that this was almost completely worthless in most cases. What's the point of taking workers off of a deactivated geyser, just to put them back on the next one? If the mineral lines are saturated, you don't get any additional money from it.

So not only was this not a very imaginative idea, it also didn't actually do its job.

Evolution: Spawn Larva

At BWWI 08, the Queen was given a new power, one I didn't mention in the Zerg section. She could cause a larva to become a Mutant Larva. A Mutant Larva was a giant larva that could move around. It even took up supply. But, as with a normal larva, the Mutant Larva could be used to produce any unit. And it did so with a modest build time improvement, much like Warp-In for the Protoss.

This was fairly interesting. The fact that they were produced one at a time directly from regular larva meant that you couldn't really use them to enhance current production speed. Turning a larva into a Mutant Larva didn't give you more larva; you still had just one. The ability was primarily about locality of production.

However, it did allow you to trade current production speed for future production speed. You could stockpile Mutant Larva, so that you could have sudden bursts of production. Since Mutant Larva cost supply themselves, you couldn't stockpile them forever. But it was a nice sentiment: being able to preserve some larva for the future. Granted, you'd still die by doing this, since current production speed is almost always superior to future production speed in an RTS. Those Mutant Larva could have been Drones, after all.

BlizzCon 08 showed us a version of Spawn Mutant Larva that would be much more familiar. The new version is cast on a Hatchery/Lair/Hive. This causes the building to (eventually) create 3 Mutant Larva. Though these guys no longer took supply, they still retained the other benefits: movement around the map and a small production speed buff.

I can just imagine the day that this change came through in Blizzard's offices. David Kim loads up the latest SC2 build, reads the changelists for what new toys he has to play with. He sees this ability, immediately switches to Zerg, and starts destroying everyone.

It's Zerg day in the Blizzard offices!

What's interesting here is that this wasn't originally intended to be a "Macro Mechanic;" it was simply appropriated as such later. Indeed the abuse of Spawn Mutant Larva may have been what inspired Blizzard to move to race-specific macro mechanics in lieu of those horrible gas mechanics.

Punc-E: Proton Charge

The Terran macro mechanic doesn't really need much discussion; it shipped in the form it initially took. The Protoss mechanic very much did not.

The first Protoss macro mechanic was called Proton Charge. It was an ability of a building called the Obelisk. Blizzard said that they had been playing around with something called a Dark Pylon for some time; they tried to give it various cloaking-related abilities to no avail. So they repurposed the building for Proton Charge.

Proton Charge was an AoE ability that was cast on probes; this caused them to glow. While they were charged, they would gather an additional mineral from mineral patches. The charge didn't last too long, so you had to regularly recharge your probes.

Comparing this to Chrono Boost shows how limited Blizzard's early thinking about macro mechanics were. CB has many uses; when and how to use it is an integral part of Protoss build orders. Maybe you save some CB and double-Forge to fast upgrade. Do you save some CB for your first Colossus, or use it for Thermal Lances and have a later but stronger push? Or maybe you just boost some Probes and power your economy.

Proton Charge was just something you did to keep up; Chrono Boost is something you do with a plan. Chrono Boost is really the gold-standard of macro mechanics in this regard. And I don't think it's a coincidence that CB is both the best and the most recent of the macro mechanics to be implemented.

Over the course of the latter part of SC2's development, Blizzard learned not just to make macro mechanics, but how to make good ones.

[Nicol Bolas]

Conclusions

So, what can we deduce from all of this information about how Blizzard designed SC2?

Zerg Fail

It is conventional wisdom that the SC2 Zerg are the least interesting of the three races. They have the fewest units, they have a lot of returning (or slightly modified) units, and they have the least interesting mechanics and spells.

What we can see from our look at the Zerg is that this didn't happen because of a lack of imagination by Blizzard. After all, we saw that Blizzard had plenty of ideas for the Zerg. The problem is that most of these ideas failed.

Corruptor? Failed. Roach as non-high Hp tank? Failed. Nydus Worms as the only transport mechanic for the Zerg? Failed. Unique Queen as builder of base defense? Failed. That Zerg siege unit we never got to see outside of the old Infestor model? Failed. Etc.

Now there were some concepts that did work, such as the use of Creep going from a pure detriment in SC1 to a benefit that you actively manage in SC2 (well, your mileage may vary on whether you consider the Zerg unit creep speed a bonus or a penalty). But by and large, whenever Blizzard got creative with the Zerg, it didn't work out.

Kill Your Darlings

There is a well-known piece of advice for writers called "kill your darlings." This does not mean that writers should happily have their beloved characters die brutally and painfully (well, not always). It means that writers should be willing to remove anything that makes the story better or flow more smoothly, even if it is one of their best written paragraphs or a particularly beloved scene.

This applies to more than just writing, of course. And this is a lesson that it is clear that Blizzard did not quite apply in the development of SC2.

Looking at how Blizzard designed units, it seems apparent that there were two phases of unit design: the experimental phase, and the in-game phase. When a unit concept was still experimental, Blizzard clearly felt willing to cut it if needed. But once it was declared to be in-game, it stayed in the game.

How many units were we shown that were actually cut? Precious few. Even if we count the Star Relic and Tempest as being cut rather then reworked into other units, that's only 5: Tempest, Star Relic, Soul Hunter, Predator, and Lurker. And of these, only the Lurker was cut after 2007.

Obviously, Blizzard internally designed more units than they showed the public. Indeed, Blizzard probably had a policy of not showing off units until they were likely to make it into the final game. Even so, it's telling of the development process that, over the space of more than two years of game development, from late 2007 to early 2010, that only one unit shown to people was cut.

It seems like there was a big push by Blizzard that, once a unit entered the "in-game" status, they were keeping it. No matter what. This is an understandable policy in the abstract. After all, high-quality visual design, models, and textures are expensive. You don't want to have your artists and animators working diligently on some unit for months or even years, only for you to just cut it and waste all of that effort.

However, this argument doesn't fly for one very important reason: you can reuse models. Cutting, for example, the Roach as a unit does not mean throwing its model away. It means designing a new unit with a new purpose from the ground up. That unit could certainly use the same model.

Blizzard even did this at least once. The original Infestor model had been intended for a Zerg siege unit. One that was cut before the Zerg reveal. They simply repurposed the model for the Infestor. Now yes, they did replace this model eventually, but that was mainly because of fan outcry. The original model looked too WarCraft-y, and again, nothing gets the Starcraft community more riled up than anything that even has the minor appearance of WarCraftiness. Blizzard themselves would have been happy with using the old model, which is why it stuck around for as long as it did.

Even so, look at the Corruptor. This is a unit concept that never really worked. It went from being a ground unit to being a flying unit. Its corruption mechanic never seemed to really work, yet Blizzard kept it in the game untouched for quite some time. The original corruption mechanic was still in the game at BlizzCon 08, and it hadn't changed since the initial Zerg reveal. It isn't known exactly when it was changed to the beta's Corruption ability, but that's still over half a year with a non-functional mechanic. And even when they changed it, they never got a mechanic that really synergized well with anything. This is a unit for whom the writing was on the wall in mid-2008.

The Roach was the same way. They kept work shopping the Roach's regeneration and location in the tech tree, to the point where their only solution in the end was to make a unit that was the antithesis to everything they initially set out to do. The Colossus was the same.

Blizzard was unwilling to kill certain unit concepts for art reasons. Once you're locked into the Protoss having a gigantic walking Tripod-esque thing, that limits what you can do from a game design perspective. But no such art reasons explain the Corruptor or the Roach.

That being said, perhaps one should be a bit more forgiving of Blizzard in failing at this. Other aspects of SC2's development suggests more than just a lack of wisdom on Blizzard's part was at play here.

Release Date

When you're about 6 months from shipping a game, there are certain things you're no longer willing to do. This is a matter of simple practicality: if you're going to hit a release date, you need to employ disciplined development. So you can't just do the same kind of stuff you were willing to do before.

This is what the Alpha, Beta, etc stages are supposed to mean. These terms have been misused to the point where one can no longer talk about them without defining the terms explicitly. Alpha is supposed to be the point in development when your product is "feature complete." It has all of the stuff that it is going to ship with. How you define "stuff" depends on what kind of product you're talking about. A level-based single-player game would be in Alpha if you can play through all of the levels, all of the AI characters are there, all of the weapons/items are there, and all of the events that you expect to happen actually happen.

The game is certainly still buggy at this point. But the game also may not be fun yet. Post-Alpha is a time when you can play with the how levels flow into one another, how progression works within levels and between them. You can move enemy spawn locations around, move item pickups around, etc. What you cannot do post-Alpha is actually change the physical level structure. You can't add levels, new AI characters, weapons, etc. You can cut these things, but you can't add them anymore.

Beta is supposed to be the stage when you first say that you feel the game is at least theoretically shippable. The gameplay is as polished as you intend to make it. Post-Beta, the only kinds of changes you are allowed to make are fixing bugs that are stop-shipment bugs.

The point of all of this is that there comes a point in development, based on time until release, where you can no longer make certain kinds of changes. A game like SC2 would probably have hit Alpha about 6 months before shipment.

So when did SC2 hit Alpha? It would seem obvious that it hit Alpha a few months before Blizzard released the SC2 Beta. However, if you look at how SC2 developed, it might seem that the game reached Alpha a lot sooner than that.

Compare the SC2 Beta build with the BlizzCon 08 build. While there were certainly many differences, particularly the macro mechanics, it would not be a very foreign experience for players. Most of the BlizzCon units had the powers and abilities that they had in Beta. Probably the most drastic change outside of the macro mechanics was the Roach/Hydralisk tier switching (Hydras at BlizzCon were Tier 1). That, and the loss of the Lurker.

For the most part, the differences between the SC2 Beta build and the BlizzCon 08 build are the kinds of differences you saw between the SC2 Beta build and the SC2 release build: different spells and stat tweaking.

Now compare the BlizzCon 08 build with the BlizzCon 07 build. Even ignoring the fact that the 07 build didn't have the Zerg in it, there were massive differences. The Terrans were radically different from their 07 incarnation. They had Medivacs and Marauders, fundamentally changing how you play the race. They had Hellions and Thors instead of Factory-produced Vikings and Cobras. The 07 Terrans were a very different race from the 08 Terrans. The Protoss had fewer changes.

What seems clear is that, at some point in early 2008, Blizzard intended to ship the game in late 2008. Or at least to have the SC2 Beta out by then. In order to do that, they would have had to declare the game to be in Alpha at some point before late 08. For an RTS game, Alpha would be the point when the experimentation ends and you're formally invested in making everything that's currently in the game work (or cutting the parts that don't).

Now, anyone who has played the BlizzCon 08 game knows that, from a visual standpoint at least, the game was not ready to ship. And Blizzard themselves knew that, so they delayed the game. And that's where the problem starts.

If you decide you need to be in Alpha about 6 months before releasing your SC2 Beta, then you cannot go back to pre-Alpha unless you know you've got more than 6 months before your beta. Indeed, going back to pre-Alpha at all is hard once you've decided you're in Alpha. I'd say you would need a 9 month lead time, minimum, before you can meaningfully go back to pre-Alpha-style development. After all, how much experimentation can you do if you have 1 month till Alpha again?

And that's the problem. Blizzard intended to release in late 2008 but didn't. Then they intended to release in early-to-mid 2009 but didn't. Then they intended to release in late 2009 but didn't. They finally released the SC2 Beta in early 2010, almost a year and a half after their originally scheduled release date.

Basically, for a year and a half's worth of development time, it was perpetually 6 months to Beta.

If Blizzard knew from mid 2008 that they were going to delay the game for a year and a half, they could have made so many more comprehensive changes. They could have gone back into a pre-Alpha mindset, creating whole new units and such. And while the macro mechanics did come online in 2009, it's still clear that they were trying to be as conservative as possible with their changes overall.

Remember that the purpose of declaring Alpha is to actually ship the product on time. You declare a product to be in Alpha so that you prevent the development of ideas that would extend the time it takes to ship. A product trapped in a perpetual Alpha is actually failing at the intended purpose of being in Alpha.

It's not known what specifically was responsible for the cascading series of delays. But whatever it was, that time could have been used much more effectively if Blizzard had simply delayed the game for a year initially, rather than letting the design stay trapped in Alpha.

Blizzard isn't stupid of course, so whatever it was must have been something that they kept thinking they could resolve fairly quickly. Or there were a series of independent problems that kept pushing back the release date. That is, they would find one problem that forced a small delay, then fix it. Then they found something else, delayed again, then fixed it. And so on. Or possibly a combination of the two.

[RamiZ]

No time now, but I will gladly read these walls of text when I get home!

[JackhammerIV]

I've briefly skimmed through it. It's a great writeup.

[n00bonicPlague]

I'll read it in its entirety later, but, from what I can tell of the bits and pieces I scanned, it looks great.

[Todie]

Finally some epic god-damn walls of text worth reading!

... i only got through the protoss part for now but i look forward to reading the rest later.

The nostalgia!


... I remember the times. It seems like an accurate and to the point historical reseprentation with just the rgiht amount of analysis to keep ones interest up, ofcoruse, largely in line with the discussion we were having way back when at Blizzforums.

... i had a sudden though while reading about the colossus though:

The Colossus is a pretty high-tech unit. By the time it comes out, low-Hp units will be out by the dozens. Even if the Colossus delivered its 144 damage spread perfectly over Zerglings, it would only kill 4 of them per shot. That's not a lot. A Reaver could kill 12+ tightly packed Zerglings in a single shot (let alone what they could do to Hydralisks), while still being very effective against single targets. So this version of the Colossus was comparatively not exactly cost-effective.

Indeed, this shows that the idea itself was fundamentally unworkable. You could make the Colossus's attack stronger, dealing 24 or 30 attacks in 12-point bundles per salvo. But that comes out to 288-360 damage per attack. This would make it really effective against high Hp units, thus taking away from the Warp/Void Ray.

... i wonder, could this idea have been forced to work using a very high damage bonus against light? ... i guess, the the main obstacle would be the randomness of what units got targeted; if the beam "got stuck" on an armoured unit instead of continuing to smelt the light ones one by one, it might make the whole thing quite impractical...