[G]TvZ - A 4-rax Biomech

1) Zerg is weakest IMMEDIATELY after an engagement. If you win an engagement, however marginal, box and GO. You have exactly 27-47 seconds to do damage before zerg can have reinforcements; during this time you can do drone damage, snipe queens, kill off creep, etc.
2) Zerg CANNOT kill off a huge marine/tank push AND a drop in the main AND a drop at the 3rd. In order to engage, the zerg has to bring a lot in order to win. That being said, drops allow your army to move forward and your army moving forward allows your drops to be effective.
3) The more early aggression you do, the later the drone saturation occurs. This means that you can ACTUALLY keep up with the zerg economy if you're doing pressure.

A 1rax expand. I don't use food timings, but I will give the most specific timings I can:
10 depot
12 rax
15 orbital
16 CC
16 depot
20-24 additional 3 rax
Constant marine/SCV production until 7:00
@7:00 attack + 3rd CC + all 4 gases (can be staggered)
Add Factory, double ebay, and add-ons
Starport, +1/+1, stim/CS (letting the factory sit idle)
@12:00 attack with MMM + take 3rd
@3rd base (~12:00), add 2 gas, 3 rax, and start tank production
@hive tech, add 1-2 factories, start thor production

With the first 2-3 marines, it's important to look around for overlords, hold the watchtowers, etc. When you scout his main base, you should be able to note the amount of initial lings and decide whether or not you need a conditional bunker at your natural. Generally, this is if you see 6-8 lings pop out.

With a standard scout after barracks, you have the ability to scout freely until about 4:00. If zerg DOES NOT put down a gas before 4:00, we know reliably that he can't have zergling speed until ~7:00, 3 minutes after the first gas is put down. This means we're free to go on building 4 rax, delaying OUR gas until 7:00.

The key at this point is to make sure you hold your watchtower. Marines will be able to deny individual and small groups of lings access to the tower. This does 2 things: allows you to get a scout out to the 3rd base of your opponent, and lets your 7:00 attack come as more of a surprise.

Scout the 3rd around 6:30-7:00. If you see it, move out with ~17 marines @7:00, rallying the rest to your bunker in case of some kind of odd counterattack.

When you push out at 7:00, the 3rd will be building, it may even be done or nearing completion. With 17 marines versus a handful of queens and slow lings, you should be able to do some damage, most of the time even killing or cancelling the hatchery. Kite the slowlings as much as possible and stick to walls to avoid getting surrounded, normal stuff.

If, at the very worst, you lost all of your marines and didn't kill the hatchery, NO PROBLEM! You forced a lot of lings, killed a lot of them, and probably also messed up some injects as well. In addition, you delay that hatchery as a useful hatchery for a little. At home you've been teching up, making SCVs out of 3 orbitals, and MULEing. If you timed this well and didn't micro horribly, you should find that you are actually even or close to even in the worker count by 9:00. CELEBRATE.

If, at the best, you kill the hatchery and maybe any defense, etc, don't feel pressured to attack into the main. You have an economy advantage now with a secondary MMM attack incoming. Just pull back, leave a marine to spot the 3rd. You can patrol around the ramp and stop creep spread for a little, but don't let your marines stay there too long and don't attack into a spine crawler.

During your initial attack, you should have 4 gases up, building SCVs, and starting to get your tech up. @100 gas, you put down factory + 2 ebays, followed by 2 techlabs shortly thereafter. During this time, you're getting EVERYTHING at once...kind of zergy style. By macroing correctly, you're at about 50 SCVs by 9:00, and should actually be even with the drone count if your attack went well.

@12:00, your first pair of medivacs comes out, making your marine/marauder safe against zergling/baneling. Check by your 3rd, expand and start moving out to your opponent's base.

Most people at this point would be worried about a bunch of zergling/baneling just sitting in the center of the map, but IN MY EXPERIENCE, because we did that early attack and delayed the drone saturation, zerg will just be finishing drone saturation and actually have almost no units out at this point. You can actually just go straight for the jugular and start attacking directly into his base, ignoring most of the creep spread. We can start being BEARSHIT aggressive.

If you ever find yourself in a situation where you don't think you can spread well enough and trade, just load everything up in medivacs, drop somewhere else. Without the aid of infestors/mutas at this point in the game, zerg is powerless to stop the medivacs.

Behind this pressure, we're securing a fairly safe 3rd, making walls, rallying to the natural with constant MMM production. Seriously, don't stop making medivacs...you should have like 12. +2/+2 is going up, +1 vehicle weapons are started, and tanks are starting to get produced. Yay!

After this attack, the goal is to be constantly aggressive, sending drops and macro pushes EVERYWHERE. Remember the principles from earlier as you move armies out, drop in the main, etc. The idea is to delay the lategame and use constant aggression to fuel the infrastructure needed to switch to your lategame composition, including upgrades/factories/starports. During this time, you're getting +3/+3 for bio and vehicle weapons, ship weapons when you finish +3 vehicle attack. This will set you up for your MMM/thor/viking defense against BLords.

Think of a marine/tank army as a mobile anchor: you can push out to the middle of the map (with the help of drops), get close to a ledge or an easily accessible choke, and start dropping from your main army. The zerg CANNOT engage both your drops and your main army. Against mutas, you can generally settle for more direct engagements as marine/tank is superior in straight up engagements with good positioning.

Remember to constantly presplit and always take note of your unit positioning. You want to be everywhere at once, and more importantly, everywhere the zerg isn't. This is by far the hardest part of the game that will require a lot of APM and multitasking to smoothly continue attacking while producing/teching. This part will be frustrating and difficult because it will feel like the zerg can always crawl back into the game no matter how much damage you do. Just remember to keep attacking.

When hive begins morphing, the lategame has officially begun. Begin replacing your tank production with thor production off of 2-3 factories while continuing to push. This will ensure that you have the thor counts needed to combat an early ultra push or early brood lords. Either way, though, all the aggression you've been doing all game should delay these lategame armies quite a bit. The midgame is ~12:00-16:00, 16:00 being about the general timing of hivetech.

You can continue attacking until an actual BL/infestor army takes shape. At that time, you want to pull everything back, build a bunch of defensive bunkers, take all the expansions on your side of the map, and just play very defensively with MMM/thor/viking.

With 3 starports (2 with tech lab), you can start the lategame air transition. I personally like going through BC first because Ravens require upgrades, energy, and a ton of gas (relative to build time), all of which takes time. You can free up supply for the air transition by trading drops (which are generally good against BL/infestor anyway. The goal at this point is to defend with mostly metal while trading your bio for air. Continue your vehicle/ship upgrades. On 10 geysers, you can transition with double ups. You also want to be getting the infrastructure for BFH, the final piece of the puzzle.

After sacing SCVs, trading drops, keeping BL/infestor at bay, your final composition should look like hellion/thor/viking/BC + Ravens in the late late game. With this composition, just move your way slowly forward and starve the zerg player using cost-effective engagements, turret rings, and planetaries in chokes.

Your final infrastructure should look like: 5 bases/10 geysers, 8 rax from the beginning of the game, 3 techlab factories, 1 reactor factory, 1 reactor starport, and 2-3 techlab starports. You should have 3/3 bio, and at least 3/0 mech and vikings. You should also have a healthy number of orbitals, about 8, in order to continue MULEing. Planetaries can be used at chokes, etc. The extra barracks also allow you the flexibility to go back into marine production should the super late game end up with base trady situations and low resources.

1) If your opponent opens with an early gas, completely eliminate the 7:00 timing from the build. You'll want to take 2 gases fairly early, get CS/stim and marauders, and prepare for a potential bust. When you get your first 2 medivacs, move out, take your 3rd, and start your aggression. The initial attack will have a lot less power to it and will take you a lot longer to get across the map effectively, but you still set yourself up for an aggressive midgame.

2) If, after you destroy you opponent's 3rd with the 7:00 timing, and they just sit on 2 bases, they can either be doing a followup HUGE bust or going for some kind of 2-base tech. The best way to handle either is to just play conservatively, making sure your wall is well-defended and you're prepared to handle 2-base muta/ling or infestor/ling at ~11:00. If you're against mutas, you can stop marauder production and start tank production, going for more direct marine/tank engagements.

3) If you get busted really early by a baneling or a roach bust, all you have to do is survive until your upgrades/medivacs finish. One thing that is always frustrating is being busted over and over and over again, feeling like you can't get on your feet. But just remember that your tech will catch up and you'll suddenly be just fine.

APOLOGIES! My computer died recently and I lost all of my replays. I will try to get some out as soon as possible. AND NOW DROP.SC IS HOLDING MY REPLAYS HOSTAGE WTF