mech thoughts from a master terran TvP

I've found that by far the worst map to mech on is slag pits. The third is extremely far and you can't defend it and your natural simultaneously like you can on other maps. Furthermore, the multiple pathways means protoss can almost always just go around your army. The best maps are typhon and LT. On typhon if you can control the watchtowers you cut off half the map for protoss and it's pretty difficult for them to bypass your army without being completely obvious about it. On the new LT there's only the single watchtower in the middle, which again makes it easy for you to control the map. The ditches where the old towers used to be are also really useful for sieging your tanks, because they block chargelots for your tanks.

The biggest strength of opening mech is that it's incredibly powerful defensively. 4gates can't do shit to a tank expo. Vikings nullify VR openings. Aggressive 6gates are always sentry heavy, and fail spectacularly because you've got nothing to forcefield.

This is my basic build order, assuming constant marine and scv production:
12rax, 13gas, 13 scout, 15oc, 16 depot,(cut a marine here) factory at 100gas, 23 depot, hellion out of the factory

Here it branches. I use the first hellion to scout. If it's a single gas from protoss and they haven't got a nexus, I make 3 bunkers at my ramp, take my second gas, and make tanks. If it's double gas then I make a starport, and then a single bunker at my ramp, and go up to 3 hellions before getting tanks. If there's no stargate, I make a medivac and drop them with 8 marines while harassing with the 3 hellions. That works best on close air like scrap or metal.

I make another CC when money allows, since you'll pile up money pretty quickly off of 1/1/1. After I've made a CC, I'll start a second factory and an armory. After the armory is done and +1 weapons is started, I add on 2 more factories and a reactor on my starport. So my 2 base production is 3 factories with techlabs and 1 factory with reactor, producing tanks and hellions. If you scout a robo bay, then make a reactor on your rax and switch it with your starport to make vikings. However, tanks are still great defensively vs colossi (watch the game vs RevYoDa on typhon for an instance of a colossi allin vs tanks)

Around here I aim to take my third and turtle my way up to 3/3 200/200 mech. You should go up to around 8+ factories once you have your third. It's actually really important to keep a low scv count. Mech is really expensive supplywise, so I try not to go over 55ish scvs. Don't be afraid to send your scvs to the protoss natural if you feel like you've got too many. You're going to be incredibly gas limited, and hellions aren't the greatest mineral dump in the game. You can also afford to stop muling and just scan once you've got your third up. Try to look for mass stargate, because mech sucks cock against carriers. If you can catch toss teching for carriers then push as hard as you can and kill his natural, because fighting carriers is a real uphill battle without air upgrades on your vikings. Also do not be afraid to unsiege, pick up everything, and just go for it if you scan his army and it looks small. Because it probably is small because he's teching to something bullshit like mass voidray or carriers.

Your main composition should be tank/hellion, with a couple of vikings for colossi. I don't think thors are all that useful; I'd rather have 2 tanks or 3 hellions for the 6 supply the thor requires. I'd say they're only really necessary vs phoenix colossi because you're not going to have any other unit that can actually kill the phoenixes. Against phoenix colossi you're also going to need ghosts; you have to emp the phoenixes or else you're going to get 12 of your tanks lifted and then you die instantly. Against mass mass immortal you just need a couple of ghosts and spam emp. Mass colossi gateway I feel is the best and least risky way to fight mech. If they get a good engagement and a good focus on your tanks it's pretty much GG. There's not much to say about fighting that except to try and position and spread your tanks out a bit so he can't hit more than one or two tanks with his colossi splash and try to emp well.