This strategy revolves around one of the Cybran Experimantals, the Proto-Brain. In the vast majority of games, it's somewhat useless, but in a game with a full, 20 minute rush timer, it's one of the most useful things you can possibly have.
To start, just like every strategy, practicing in a skirmish game is highly advised. Most concrete strategies (stratagies which follow any specific build order and allow for very little deviation) are hard to pull off against even a "normal" AI, much less an "easy" human, unless you've been granted super powers by the gaming gods, so you should always test any strategy besides the obvious "just counter whatever your enemy is doing" offline in a couple skirmish rounds first.
To begin, let me reiterate what I stated earlier: this strategy pretty much requires a full 20 minute rush timer. If you are playing against a human who won't agree to that, this might work, but more than likely not. That said, start by building your normal 4 mexes (Mass Extractors) and 4 generators, then focus on building either 4 or 5 normal research stations. After you have the research stations completed, reclaim your 2 engineers with your ACU, and then move to an area near where your Proto-Brain will go. Then get comfortable. I know, most people would NEVER tell you to sit idle for several minutes duing a rush timer, but that's exactly what I'm saying. Your sole mission now is to research the Proto-Brain. Everything else you can do will consume mass and energy that you don't want to waste, so just sit there and research until you can build the Proto-Brain. The second you can build it, build it.
Once you have the Proto-BrainEdit
Now, with the proto brain constructed, you should be around 11:00 into your 20:00 rush timer, though I have done this as early as 8:00 and as late as 13:00. You should also be gaining 1 research point every 4 to 5 seconds. Some basic math tells us this means you will gain 180 research points by the time the rush timer expires. This is enough to finish the structure tree, the entire ACU tree, all of 1 of the other 3 trees. Depending on the map you're on, you might want to do either Land or Air. Besides spending your plentiful research points to gain a decisive advantage over your opponent - without spending any mass or energy, I might add - you'll now need to build the remaining majority of your base. Without engineers, this would seem impossible in 9 minutes, but you have 1 more trick up your sleeve.
First Upgrades: ACU Construction Speed & CostEdit
First, research all the upgrades to build time and/or cost you don't already have in the Structure tree. Then, do the same in the ACU tree. You should be able to finish these in 1 minute. Now, your ACU can construct buildings in 1/2 the time of a normal ACU, and 1/3rd the time of a normal Engineer, meaning that what you can build in your remaining 8 minutes is now almost as much as your opponents could in the last 16 minutes, maybe more. Of course, a few more energy gnerators, any outlying mexes, and a lot of shields are advised, but after you finish the core of your base, you're left with a lot of defenseless buildings. The solution is obvious: fortify the Proto-Brain!
Making the Proto-Brain an inpenetrable fortress.Edit
Due to the way shields overlap in SC2, one good tactic here is to surround your proto-brain with a ring of AA turrets, then a ring of shields, and finally an outer ring of land defense turrets. Then, right before your opponent's first attack reaches the Proto-Brain, seperate the brain, but let it hover in place. Your defenses will gain increased veterancy at an alarming rate, quickly doubling their damage output within the first 5 minutes after the rush timer expires. This will make your proto-brain complex totally inpenentrable to everything except long range artillery (basically just fatboys and battleships) or a mighty large number of experimentals. Of course, you can also place a nuke facility directly adjacent to the brain, within the ring, or even 4 of them in a cross shape, so that the Tactical Missiles will help ward off even the enemy artillery, and obviously protect the brain from a nuclear strike. If done properly, nothing short of 10 fully stocked nuclear missile silos will be able to destroy the Proto-Brain, and let's face it - nobody has that. Getting to this point in under 20 minutes isn't easy, but it can be done, or at the very least, you can get enough of this completed to ward off your enemy's initial assault and finish it shortly thereafter.
Finally, go fourth!Edit
You are now roughly 25 minutes into the game. Your opponent probably has a decent army of their own constructed, but if they attempt to use it, your Proto-Brain fortress will decimate it. They cannot nuke you to death because your defense against that is flat out excessive. What can they do? Well...nothing. Even better, you now have every item of research in the game. So, what do you do? Well, for starters, you can go for a multi-nuke victory, as your silos used to defend your Proto-Brain fortress can also launch nukes - 20 of them if fully stocked. You can also add on to the fortress with an Experimental Air Gantry and surround it with the same defenses surrounding your Proto-Brain, then spam Soul Rippers. This can double as good defense against AC-1000 Terror gunships, which your opponent might try to use to take out your hovering, detached Proto-Brain. Or, you can create a forward artillery base using your ACU (now very heavily fortified due to the full upgrade tree) and use it to pummel your opponents into oblivion. Of course, you could just wage a classic war of attrition, safe in the knowledge that your base is practically invincible and eventually, when someone loses, it won't be you. The choice is yours.
But there is one weakness.Edit
The key to this strategy is to get a jump on your opponent's technology. This works only because, while you will have fewer of everything - mexes, energy, turrets, tanks, gunships, everything - everything that you do have is twice as good as that of your opponent (and cheaper than his, too.) That said, Cybran is still the faction of early rushes. Sure, you can sit back and soak up damage for hours if you want to, but eventually, your opponent will put so much damage on target that the fortress will fail. It'll probably cost him 10 times what it cost you to make the fortress in the first place, but eventually, he will destroy it, and you'll be left with practically nothing when he does. That said, there is an easy solution to this - strike early, THEN strike often. The best use of this strategy is to first fortify your position, and then as soon as you can (without leaving your base undefended) hit your opponent hard. This can be done with a single, well timed early nuke launch, or the deployment of a battleship from a naval yard you stuck way off on the edge of the map. Whatever you do, you have to strike him hard, and preferably within 5 to 10 minutes of the rush timer expiring. Your goal is to throw him a curve ball here. It MUST be something he doesn't expect. This attack is purely psycological. If it can wipe him out, great, but that's not the intended effect. It's just to divert his attention for a couple minutes (hunting down your previously undiscovered naval yard, for example.) This buys you 5 minutes and draws out his forces. Once you have this oppritunity, strike with a small group of gunships and take a route that's not directly from your base. Your goal here is to take out one, single structure. Again, if you can do more, fine, but you're not really trying for that. Keep hitting him with small groups of basic units. Ten loyalists here, five renegades there. Make him think he can't afford to attack your base without risking his own and the torrent of light assaults will never end. Finally, take the group of 20 soul rippers you've been constructing the whole time and wave goodbye. Hopefully, you did all this and your game timer hasn's passed 59:59 yet. Why? Because by 1 hour into the match, your opponent will have caught up with your technological advantage, and if they're playing anything besides Cybran themselves, you're screwed. UEF units always have more health and do more damage, and even with the TMLs, Fatboys will play hell on your defenses. Illuminate opponents can send in 3 darkanoids. Yeah, you'll shoot them down, but their air crash damage alone will destroy the entire Proto-Brain fortress. The problem here is simply that you're playing Cybran. Cybran's don't turtle well, they rush well. The Proto-Brain fortress will buy you about half an hour but if you haven't hit your opponent pretty decisively by then, this was all for nothing.
This strategy is one of many when playing Cybran. It's key strength is that it's unexpected. Most SC2 players assume when they see a Cybran player they're dealing with an early rusher. While this is still true, they won't expect a heavily fortified base, nor will they expect you to have completed the entire research tree before you fire a single shot. So when that first shot and every shot thereafter it hits really hard, it'll throw them for a loop. Then, you hit them with a random battleship or nuke, and their suprise turns to dismay. Finally, after you occupy them for a while with light attacks to distract them, you deliver a final knockout punch, and their dismay becomes disbelief. That said, it's not undefeatble, and it can be easily countered. In fact, after an hour, this strategy will practically ensure your loss, but then again, if you're playing any strategy as Cybran after 1 hour, you're lucky to still be in the game. So basically, this is a variation on what is otherwise basic Cybran stragegy. Think of it as a rush, but smarter.