If you thought the Black Zone was a confusing labyrinth, you're in for a treat.


Before we head into the Yellow Zone, lets grab the stuff we need:
Weapons - You'll need at least one. I suggest both the Magnum and the SMG, with ample ammunition.
Wi-Fi Remote and Receivers - You need one Receiver, but it'll be quicker and easier if you have two.
Screwdriver
Body Armour and Medkits - not required, but always good to have on you.
Most importantly, the Gas Mask - without this, we can't even enter the Yellow Zone.
When stocked up, return to the Bridge.

Bridge

The Yellow Zone is accessed through the Green Zone - so, hop down from the Bridge onto the crate, through the familiar vent and to the Platform Hub.

These are the two doors we want. Head through.

Green-Yellow Connector

Before you enter this door, make sure your Gas Mask is equipped. The Yellow Zone is clouded in toxic gas that rapidly drops Haydee's health. You would be lucky to make it two rooms in without dying.
When you've put on the Gas Mask and done your very best to try not to think about how a gas mask is supposed to work on an android with no mouth or nose, enter the Yellow Zone.

Yellow Zone - Floor 1, Gun Checkpoint
Take a glance at the left turn.


No guns allowed past this point - you'll have no means of defending yourself, but there will still be plenty of hostiles.
For a while we'll be pressing buttons to lock and unlock various floors and cages, with the intention of avoiding fights while we're defenseless.
So, just throw your weapons on the floor outside the checkpoint.

Don't worry, you'll be able to come back and get them later.

Enter the gun checkpoint and hit the button. If you hear a beep, it means there's a gun still in the checkpoint. Otherwise, the gate will shut behind you and the path forward will open.

On the left as you pass the checkpoint is a rare unlocked crate containing 10 Magnum Rounds.

On the right is a door, with a button on the wall to the right of it.
The Yellow Zone, in places, can be quite dark, but don't equip the Night Visor if you have it - you can't use it here without taking damage from the gas. If you have it in your inventory and you really can't find something, you can flick it on for a quick second to get your bearings while only taking minimal damage.
You should be fine as long as you can find this button - it's the only really hidden thing in the Yellow Zone.
Hitting it will lock the door next to it. That's what we want. Once locked, return back to the gun checkpoint.

Pass through it again and leave your weapons on the ground. Head to the left and into the next room.

Floor 1, Save Hub
Up until this point, it's been easiest to use a combination of letters and numbers to label rooms. In the Yellow Zone, it's a little more frustrating - I'll mostly be labelling rooms based on the floor they're on.

There are six floors, all labelled through 1 to 6. We're on the bottom floor currently - Floor 1. Each floor has a 'pair' floor - only one of each pair can be unlocked at any time. By locking that door earlier, we locked Floor 1, and unlocked 6. You'll see why in a moment.

You can head through this door on your right to save your game, if you didn't before.

Where we want to be is directly opposite the save room.

Floor 1, Receiver Room

That lit-up 6 above the door indicates why we locked Floor 1. By unlocking Floor 6, we also unlock any doors in the Yellow zone labelled with a 6 above them.
Most of the time, labelled doors simply contain hostiles, but here we progress. Head into the cell beyond the door.

On your right as you walk in you can find a button that opens up a grate containing a Wi-Fi Receiver obtained from elsewhere.

On the other side of the room you can find a... is that cake?

Hit the first button to open up the Wi-Fi Receiver grate and head back into the previous room.

Floor 1, Save Hub
Climb up the boxes around to your right and back to the door to return to the gun checkpoint.

Floor 1, Gun Checkpoint

Head through the checkpoint and hit the button to the right of the door again to unlock it and continue.

The Tower

The Tower is a long vertical shaft with six doors, all labelled 1 through 6. There's also a vent above 6 that serves as an alternative entrance to 5.
That's where we switch power around, so climb up ledge after ledge and enter the door labelled with a 5 when you reach it.

Floor 5, Switch Room

There are six buttons, each corresponding to a floor. Pressing a button will switch that floor between locked and unlocked.
Each floor has a linked 'pair', opposite of it across the room. Locking one will unlock the other, and vice versa.
1 and 6 are linked.
2 and 5 are linked.
3 and 4 are linked.
As you enter, the indicators will look like this:


Floors 1, 3 and 5 will be unlocked, and Floors 2, 4 and 6 will be locked.
We need Floor 2 unlocked, and in Floor 2 there's a Slasher in a cage labelled with a 4. That means we need the 2 lit up, and the 4 turned off.

Turn on 1, 2 and 3.


This will lock the door behind us, but you can always get in and out of Floor 5 regardless of whether 5 is lit up. Head to the back of the room and look up.

Climb onto the crates to your left as you walk to the back of the room and up onto a railing. This will pull you up into a vent. Open it up with your Screwdriver to exit back into the Tower.

The Tower

Scale back down the Tower. Don't jump from ledges, simply sprint off them one at a time.
Enter Floor 2 - I'm assuming you can count, but in case you can't, that's the one directly underneath 4 and one platform up from the very bottom.

Floor 2, Hall
Take a quick peek around the right.

You should see a Slasher in a cage, if you lit up the right numbers in Floor 5. This pattern of keeping Slashers locked out will repeat a few times.
Take the left and continue down the hall into the next room.

Floor 2, Shaft
It's like a mini-Tower.

Jump up two levels and you'll find a Haydee corpse with 2 Diskettes on her, and then start climbing down.

There's another Haydee at the very bottom with 10 Pistol Rounds - something I'm sure you'll agree is real useful right now.

On the second-to-bottom ledge there's a vent. Crawl through it.

Floor 1, Receiver Room

We reach our Receiver! Grab it, and hopefully you now have three Wi-Fi Receivers. You should definitely have two.

Head back into the Shaft, up a level back into the Hall, and return to the Tower.

The Tower

Climb allll the way up the tower to the very top, through the vent above 5 and enter.

Floor 5, Switch Room

Make sure you drop onto the crates so you don't hurt yourself. Return to the buttons.


We next enter Floor 4, and ensure 1 and 5 are locked. So, simply turn on 2, 4 and 6. Then exit back the way you came, up and through the vent.

The Tower

Enter Floor 4.

Floor 4, Hall

With the two Slashers safely locked in their cages, you can find a button on the left next to the second Slasher. Hit it to unlock the next room.

Floor 4, Deposit and Save Point

On your right in this room you can find a Save Point. There's no Item Box, to prevent you from using it to magically warp your weapons into here, but if you picked up the Diskettes from the Haydee back in Floor 2, you can save.
Progress into the next room.

Floor 4, Gate Button

There's a button in front of you that opens up a gate elsewhere. Place a Receiver on it and head back out.

Floor 4, Deposit and Save Point

There's a little box on the right but it doesn't have anything in it yet. From here, return through the Hall to The Tower.

The Tower
Climb all the way back up to the top and through the vent to return to Floor 5.

Floor 5, Switch Room
Back down to the buttons.


Unlock Floors 1, 3 and 5, then head out the door.

The Tower
All the way down to the very bottom, exit into Floor 1.

Floor 1, Gun Checkpoint

Optionally, you can hit the button at the very bottom to lock Floor 1 again. This will release a Walker's cage in an upcoming room containing a Medkit. If you could use a Medkit, hit the button - otherwise, don't worry about it.

In any case, grab your weapons from the floor, make sure they're loaded, and enter the Save Hub again.

Floor 1, Save Hub

There's a shortcut back which contains some minor loot. It's optional, but if you're interested, duck into the Save Point and grab your Pliers. This will net us a couple of Mines. If you didn't pick up the Pliers in the Red Zone, grab your Pistol instead. You shouldn't need to bring any ammo, just whatever's in the magazine will suffice. You should also grab your Crowbar for a couple locked crates.

If you're hurting for inventory space, you don't explicitly NEED your Screwdriver, but it will net you an achievement and a Medkit up ahead.

Climb up the crates to the left of the Save Point door and onto the ledge. Head through the door.

Floor 1, Hub-Gate Connector

Climb onto the lowest crate on the left and jump up to grab the railing. Shimmy all the way to the right to the other side of the room.

Climb onto the crates on the right side and jump up again to grab the top railing. Shimmy left around the corner, and pull yourself up. Enter the door.

Floor 1, Gate

The crates to your immediate right as you enter have 10 Pistol Rounds atop them.

This is the same gate we placed the Receiver for. Enter and use the Wi-Fi Remote to open it up.

We want the door to our right as we pass the gate.

Floor 1, Gate-Trap Connector

Climb up onto the crates on your left, grab the railing, shimmy to the right and pull yourself up. Enter the door.

Floor 1, Trap Room
As the name implies, this room is a trap.

Hitting that button opens up the other side of the room elsewhere... and drops the floor beneath you. As well as taking a hefty chunk of fall damage, you'll get mauled by Slashers in seconds.

Instead, walk up to the button, place the Receiver upon it, and then walk back off the grated floor.

When safe, hit the Wi-Fi Remote to lock yourself out, unlock the other entrance to the room and not incur any unnecessary deaths. Back into the previous room.

Floor 1, Gate-Trap Connector

Directly ahead of you, there's a little vent near the ceiling. If you brought your Screwdriver, grab one of the crates to the side of it, shimmy to the ledging, pull yourself up into the crawlspace, and then head through the vent into another room.

???
Oh my.

Grab the Medkit in this room and then exit back out.

Floor 1, Gate-Trap Connector
Climb back down the crates and return to the Gate room.

Floor 1, Gate

Head through the door straight ahead.

Floor 1, Gate-Deposit Connector

If you hit the button in the dark at the Gun Checkpoint, there's a Walker to your right. Kill it and loot the Haydee corpse in his cage for another Medkit.
There's a Slasher here, but he should be safely locked in his cage.
In any case, enter the door on your left as you walk in, across from the Walker cage.

Floor 1, Deposit Room

There's a Walker to your right past the crates. Kill it.

In front of the Walker, you'll find a deposit box. This is the same box you found on Floor 4, so anything you place in there now is retrievable from inside the Tower.



Yuuuup. Put your weapons into the Deposit Box, and we'll be able to smuggle them past the Gun Checkpoint and finally tackle areas with hostile robots.
You can return back the way we came, or we can take an optional shortcut back that contains some minor loot. You won't need to fight any hostiles as long as you kept Floor 2 unlocked, but you will need to disarm/shoot a Mine.

If you just want to return back the way you came, skip the next section. Otherwise, head forwards into the next room.

Floor 1, Drop

Carefully move around to the left side of the room. You'll see a drop in the dark with the telltale red light on the left wall of it. That's an armed mine.

With the Pliers, slowly inch forward with your crosshairs on it until you can disarm it, and then pick it up for 1 Mine.
If you don't have the Pliers, stand far back to the right and shoot it with your Pistol.

The highlighted crate, at the top of the drop, contains 20 SMG Rounds.
Start safely scaling down the crates to reach the lower floor of this room.

Head all the way back to the back-right side of the room and enter the door here.

Floor 1, Mine Cell

There are two Slashers in cages to your left, labelled with a 2 - they should be locked safely in. On your right there should be a cell labelled 3 that should be unlocked. There's an armed mine in here.

You need to be extra careful approaching this mine, as the scrapped robots around it may block your crosshair - find the sweet spot, disarm it and take it for 1 Mine.

The Haydee corpse slumped in the corner has 2 Mines, for a total of four from the detour. If you can only carry 3, that's still a good haul. Exit the room.

Floor 1, Drop

Turn left and cross back to the other side of the room - enter the door on your left in the corner.

Floor 1, Hub-Drop Connector

If you move around the left-side crates, you can Crowbar open the highlighted crate for another 20 SMG Rounds.

Then, climb down to the bottom, unlock the door and exit.

Floor 1, Receiver Room
Take the left door to return to the Save Hub, and duck into the Save Point to restock.

Save Point
Store your excess loot. Just make sure you don't accidentally store your Gas Mask and kill yourself.

Here's what we should be bringing:
Gas Mask - obviously. Don't even let this leave your inventory.
Ammo - we'll be doing some shooting once we retrieve our firearms from where we smuggled them.
Wi-Fi Remote and Receiver - With one placed on the gate and another placed in the trap room, we should still have one in our inventory. Otherwise we'll be doing a bit of backtracking.
Screwdriver
Body Armour, Medkits and Mines - Optionally. We don't need any of this, but they'll be nice to have for general survival while we're fighting.
At least three empty inventory spaces - two for our weapons, and one for the keycards we'll be picking up.

When you're ready, exit the Save Point, head up to the left door to return to the Gun Checkpoint, unlock and enter The Tower, and climb back up into the fifth floor.

Floor 5, Switch Board


Switch on 2, 4 and 6 to allow us to go back into Floor 4. Crawl back up through the vent, to The Tower, enter Floor 4 and pass through the Hall...

Floor 4, Deposit and Save Point

Whew. A lot of running around, but we can finally retrieve our weapons and defend ourselves here in the Tower. With these, and the Receiver in the Trap Room, we can grab both Wi-Fi Receivers.

If you didn't backtrack in the Black Zone to get your Wi-Fi Receiver back, continue into the next room and grab your Receiver. We need it for the first keycard.
Return yet again, to Floor 5.

Floor 5, Switch Board
You have a choice here. You can opt to keep the hostiles in the next floor's Slashers locked up, thus saving you some unnecessary combat. However, if you don't mind shooting a couple of hostiles, you can pocket a Medkit, a Diskette, and 10 Pistol Rounds for doing so.

If you want to avoid combat, unlock Floors 3, 5 and 6.


If you want to kill the Slashers, unlock Floors 1, 2 and 3.


Return to The Tower whichever way you can, and enter the third floor.

Floor 3, Hall

If you let the Slashers out, there will be one on your right and one on your left. The right one is closer - kill it first and then turn to kill the left.
The first Slasher's cage will contain a Haydee holding a Medkit, and the other will have 1 Diskette and 10 Pistol Rounds.

Enter the other door down the hall.

Floor 3, Shaft

Another mini-tower to climb up. Scale upwards until you reach the door and enter it.

Floor 3, Platforms

In this room we'll be jumping on a couple of yellow platforms to reach the opposite door.
I strongly suggest you sprint off the ledge to grab the platforms - by trying to jump onto them you run the risk of overshooting it and dying.

Grab and pull yourself onto the platform in the pit in front of you and then turn right to see a button on the wall.

Jump over to it and place another Receiver onto it, then turn around and jump to the other side across from you, from the platform forwards.

There's a little gap to your right under the pipes you can crawl through. Once passed, give your Remote a click. This will disappearify the platform before and reappearify it directly in front of you.

Hop onto the platform, turn to your left and jump to the door.

Floor 3, Keycard Room
Click your Remote if this room isn't already open.

You'll see this poor little guy deeply contemplating our first Green Keycard of the Yellow Zone, and second in total. He won't mind if you take it, don't worry.

Hit the button in front of the Walker to reset the trap room and allow you to get your Receiver back later on. Then, return to the previous room.

Floor 3, Platforms

Sprint off the ledge to grab the platform again, turn right, duck under the pipe and hit the Remote again to switch it back.

Don't forget to grab your Receiver again on the way out!

Return down the Shaft, through the Hall, into The Tower, and climb back up to the fifth floor again.

Floor 5, Switch Room


Unlock Floors 4, 5 and 6, head back out and head up a ledge into the sixth floor at the top.

Floor 6, Halls

Turn left. If you like, you can place a Mine at the intersection to kill a Slasher that will spawn in a moment.

Around the two next right turns is a button. Get ready to fight - when you hit that button, two Slashers will spawn. One around the corner behind you, and the other at the entrance. Only the closest of the two will attack immediately, though.

Hit the button and then turn around, killing the Slasher behind you.

The corpses in front of the button can be looted for 1 Diskette and 10 Pistol Rounds.
Turn the corner behind you and get ready at the next one.

The second you walk around the left turn leading back to the intersection, a Slasher at the entrance will rush you. Keep your sights aimed at the right side of the intersection to kill it when it attacks.

Take the intersection to the left and enter the door at the end.

Floor 6, Keycard Room

There are four hostiles in this room. Across from you is the keycard, and when you take it, a fifth will spawn.


Shooting one of the Walkers will typically cause the other Walker and one of the Slashers to attack, so when you shoot one, be prepared to quickly fight three.

Careful shot placement is necessary - if using the Magnum, remember you can get a two-hit kill on all robots, but Walkers will require a headshot.

Dispose of the fourth hostile and be ready to fight the fifth.

Grab the keycard and spin around, killing the Slasher that spawns.
Now we have three Green Keycards in total, and are done with the Yellow Zone. Right?
That depends on whether you want your Receivers back. We should have two, but we can grab one of them super quickly from the Gate room - so this is optional. It will, however, get us an achievement later on. In either case, return to the previous room and be ready to fight.

Floor 6, Halls
As soon as you turn the corner, a Slasher will attack.

It'll come from the right turn, so be ready to drop it. Then, head back to the Tower.

The Tower
Regardless of whether you're getting your Receivers back, you need to exit via the fourth floor, to avoid a bunch of extra hassle with the gun checkpoint.

Now that you have your weapons, you could go through every floor that has hostiles in cages and clear them out. Some of the cages have loot, but honestly, it's probably not worth the effort - it's mostly Pistol ammo and maybe a Diskette or two.

So, as long as you have Floors 4 and 5 unlocked, head down to Floor 4 and be ready to fight.

Floor 4, Halls

This cage has a Slasher in it, and a vent that leads back down to Floor 1 - although it's a one-way trip.
If you're not interested in getting back both Receivers, just kill the Slasher, grab your other Receiver from the Gate room ahead, head back and head through the vent, grab your other green keycards from the Item Box and waltz out of the Yellow Zone - then you can skip the next section.

Otherwise, read on.

If you didn't retrieve your Receiver in the Black Zone, keep going forwards. Head back into the Save Point, to the Gate, and put your Receiver back on the Gate button. You need it to retrieve your other Receiver, and then we'll be coming back for this one. Told you it'd save time in the long run.
With your Receiver on the gate button, head through the vent in the Slasher's cage.

Floor 1, Gate-Hub Connector

You'll come out of this little vent behind the crates in this room. Grab the railing in front of you, shimmy around to pull yourself onto the ledge, and enter the door.

Floor 1, Gate
Pass the gate with your remote and enter the door on your right.

Floor 1, Gate-Trap Connector
Jump onto the left crates, pull yourself to the ledge and enter the door.

Floor 1, Trap Room

Make 100% sure you don't accidentally push the button while taking your Receiver off it. Now we have 2/3, we can return. More backtracking.
Return, in any way you wish, to the Save Point. Don't bother smuggling your weapons.

Floor 1, Save Point
Restock, take all three of your green keycards out, and save your game if you feel like it.
Then, exit back out and return to the gun checkpoint.

Floor 1, Gun Checkpoint

Drop your guns again, unlock the door ahead by the dark button to the right of it, and enter the Tower.

The Tower
Hit up Floor 5.


You unlocked Floor 1 just now to get in, so lock it again to keep the Slasher in Floor 4 out. Then exit, and head back to Floor 4, through the Hall, through the Deposit and Save Room, and enter the Gate room.

Floor 4, Gate
Finally, you can snatch your other Receiver.

Now that we have all three Receivers, we can leave. Head back into the Hall, through the vent in the open Slasher cage to Floor 1 and past the Save Hub to the Gun Checkpoint.
Whew! Exit the Yellow Zone.

Green Zone, Green-Yellow Connector
Where we want to be is actually just down here to the right, off the ledge onto the pipes below.

This is a tricky jump. From these pipes, jump onto the lower set of pipes. Line it up with the vertical ones extending from it so you'll at least land on that if you overshoot it.

Once on the pipes, enter the vent.

Room G-1

Here you see a Green Keycard Reader, and behind a grate, a Walker guarding a Blue Keycard.
Plug one of your three Green Keycards into the Reader to open a door elsewhere. All we needed to do. Head through the door to the right of the card.

Room G-2

Time to climb up. Enter the crawlspace ahead of you and through the dark under some pipes.

Jump clear across the room to grab the ledge, and up to the next ledge.

Make another epic jump to the ledge across the room, shimmy left to pull yourself onto it.

After pulling yourself up, turn around. Sprint off the ledge to land on the closer two pipes, and then jump to the pipes further along. On them, you'll find an exceptionally well-hidden 3 Diskettes. Then, jump back to the ledge and head around the right.

In the dark on the left you'll find your door, serving as your exit back out to...

Platform Hub

Neat. Head across to save your game and restock and whatnot.


You should take out the first Green Keycard you initially had lying around in the Item Box, if you didn't already.
You can put your Gas Mask in the box - or throw it into a pit or whatever - you don't need it anymore.

Remember this button, the closest one to the save point? Put a Receiver onto it - you'll be staying one step ahead of a trick the game's going to pull on us soon.

Our next order of business is at the bottom of the Stairway.
If you don't remember the way back, it's through the vent on your left as you just entered this room...

Room B-1


Up the shaft and through the door on your right...

Room C-1; the 'Maze'

The door around to our left...

C-E Connector

Unlock the other side with the button and head through...

Room E-1

And into the darkened door on our left.

Stairway

If you jump up to grab the center structure in the middle of the Stairway and shimmy around the right corner, you can find 20 SMG Rounds teetering on the top of it.

Run all the way down, over some crates to reach the very bottom of the stairway and enter the door.

Room F-1

Crawl under the gap in the singing paips to the right of you and look up. In the dark above you, there's a Haydee corpse holding 10 Magnum Rounds.

Further down the corridor, right to the very end, you can look through the gap in the wall to the right down back the other end.
If you really want to, you can spend a very long time slowly shimmying across the room, all the way down to the opposite end, and then alllll the way back, for 20 Pistol Rounds.
I'm sure you'd agree that would be a tremendously worthwhile way to spend your time.

Honestly, just head through the door and continue.

Room F-2

Another Green Keycard Reader, this time on the other side of the Blue Keycard room. Plug it in to open up another gate and then turn right back around. Get ready to fight!

Room F-1

A Slasher is waiting for you, and attacks as soon as you enter. Kill it, and keep your gun handy.

When you approach the exit door, it will lock and another Slasher will spawn behind you. Face backwards, towards the door you just came from, and walk backwards until you see it spawn.

Scrap metal.

There's a button on the wall a little bit back which you can press to open your way back.

Stairway
Climb all the way back up to the top and exit.

Room E-1
Head back through the door on your right.

C-E Connector
Unlock the path forward again and continue ahead.

Room C-1; the 'Maze'
And again, around to the left back into the room behind it.

Room B-1

We're finally nearly done, we have just one thing left to do. Head through the wall directly ahead.

Room B-2

In front of you as you walk in, you'll see the third and final Green Keycard Reader. Plug in your last Green Keycard, causing a gate to lock and a crate to drop. Exit out into the previous room.

Room B-1

Enter the shaft again to the right, drop down to the previous floor, head back to the crawlspace and enter to the left.

Room B-2

Hoist up, crawl around the pipes to the right and you'll see where the crate dropped before. Drop down onto it and enter the vent.

Puzzle Room
I call this the 'Puzzle Room', as it's probably the only real 'puzzle' in Haydee, although your mileage may vary.

After exiting the vent and dropping down, you'll see a locked door with a symbol above it, and four buttons with various shapes.
The buttons rotate the tiles in a line away from them:


The center one can't be rotated, seeing as how doing so would be pointless.
We want to match the symbol above the door:


If you want to work it out yourself, it's not a massively challenging puzzle. If not, here's the magic solution:

From top-left down, hit the first button once, the second button twice, the third button once, and the fourth button once. You'll hear a click and the door will open.

The body to the left of the door has 2 Diskettes to take. Enter through the door, and be ready to fight.

Blue Keycard Room

There's a Walker in front of you. Kill it.

When you grab the keycard, a Slasher will spawn behind you at the entrance, so snatch it, turn around and show it what for.

Now we have our second total Blue Keycard! Now that we have both, we can progress through the final zone.
Exit once more.

Puzzle Room
Climb back into the vent and exit.

Room B-2
Back around the pipes into the crawlspace.

Room B-1
Directly ahead through the crawlspace we go.

Platform Hub

Oh no, the platform leading back to the Bridge has disappeared! How will we ever--

Heh heh heh. Nice try.

Hop back along, and head back into the Save Point. We have some inventory management to do before we continue.

In the next, and final, part, we beat Haydee.