I had to edit this guide because the game has changed a lot in the three four years since I wrote it.

Now you can run while holding the hat.
The hat doesn't disappear in the elevators anymore except for the sluices in the 'Blast Pit' chapter.
Some doors stay open now and others close behind you.
But the hat still swims on the surface.
And ladders are still a ..............



With the December 2020 update I gave Xen amother try and it worked. The saves don't disappear anymore, achievements unlock, the crashes are very few and some smaller bugs don''t really annoy. You should save often because the hat still falls through floors or becomes unresponsible, like:




But after teleporting the hat sits stable in or at the teleporter now.

Getting the hat to Xen is a bit tricky.

You will probably not go for this achievement in the first run, so I recommend you play on easy.

You will find the hat in 'Unforeseen consequences' after fighting your way back to the train station. Right behind the exit there are some pipes on the right side, you climb them and there in the corner is the hat on a platform, seen only with flashlight on.


While carrying the hat, you can not run, so best you place it in a safe place, e.g. a corner, clear the area and pick it up again. (This has changed, you can run with the hat now.)

Some doors and gates close behind you, so best you save before each door and gate. When enemies are present, you pass the gate, place gently the hat in a safe corner behind the gate or just throw it away and clear the area.

The hat swims on the surface.

The hat does not disappear. If you can't find it, you have to search harder. There are though some spots where it falls through the floor. And a corpse can cover it, but in this case it can be picked up even if hidden underneath.

The hat rolls away, so better you carry it upright and place it upright. If necessary, let it fall from a trash bin or a door step to get it upright.

Don't shoot or hit the hat. No use, it's not a gnome.

There is a problem with climbing ladders. Sometimes the hat won't pass through. Best for me was to turn around and climb backward, moving the hat around obstacles. There are some problematic ladders, e.g. in the rocket silo, you just have to find your way.



Xen expansion

Although the devs have fixed most bugs in the Black Mesa complex optimizantion of Xen in still quite poor.

Frame drops are impressive. Especially in open areas. Rarely the game will freeze completly or just shut off. The hat (or other items) gets stuck sometimes under a flower and is not responding.

Very annoying, the savefiles disappear.

So save often, don't overwrite your files until you have achieved your goals and back up your savefiles.

There are some tricky spots in the game:

Unforseen Consequences:
- In the pipes, when turning the valve and let the water rise, you can take the hat with you to the valve or place it under the hatch.
- At the abyss where you have to walk the pipes on the right hand, you can throw the hat down in the passage before entering the vents.
- Between the hanging crates there is a gap you can pass only running/jumping. There you have to throw the hat on one of the next crates. This will take some frustrating time. And safe after each successful jump. edit: has changed

Office Complex:
- You can place the hat before the electrified room and pick it up later, after clearing the area.
- You will have to jump to the ladders over the gap in the elevator shaft with the hat. It is possible, but it took me some tries. Save before each jump.

We've Got Hostiles:
- edit: Phantron remarked that you can leave the hat at the big iron door at the beginning and pick it up later
- When facing the two turrets behind the wet floor, throw the hat behind them (Mouse 1) and move on.
- If the hat disappears in the elevator floor, reload and try again.
- After coming up the elevator and entering the hangar full of soldiers, do a minimum of fighting, just throw the hat ahead and run for the bunker (edit: has changed, there are no more soldiers in the hangar). Once inside, shoot the first four marines coming and just jump down to the vent. Best take the cross shaped supports.


Power Up:
- After passing this monster robot you can place the hat behind the entrance and pick it up after you eliminated the robot. edit: has changed: now you can leave the hat in the opening area at the ladder

On a Rail:
- Drive carefully, the hat tends to fall off the cart if you go faster than first gear.
- When the car gets lifted up , leave the hat on it, take the ladder and shoot the turrets off the way.
- You can also go all the way not taking the car.
- After entering the open area the door closes behind you. You need to throw the hat out before attacking. edit: has changed

Apprehension:
- In the cooling chamber just walk through and take the pain.

Residue Processing:
- Before you jump in this radiating rotating thingy you can throw the hat up to the exit.
- Before the stamps drop the hat and run under the stamps. Took me some tries. Once the hat disappeared. edit: you can run through now

- Best save after each step.

Questionable Ethics:
- Leave the hat at exit in the lobby.

Surface Tension:
- I threw the hat down from the dam and found it later at the far end of the river at the wall. I think you can have it with you all the way too. edit: it seems impossible to throw it down down into the water now
- edit: When you get out the pipe into the open area there is a soldier beneath you now. When you jump down and lay the hat down he keeps shooting and that costs you a lot of HPs. I threw down a satchel charge and he moved back far enough
- Jump, put the hat carefully down, shoot the enemies.
- After shooting the soldiers on the platforms beneath you, you best throw the hat down.
- After you downed the helicopter and climbed up, there are these platforms... You can reach the first one only with run/jump, so you have to throw the hat on the first platform. It took me some time so you better save when the hat stays there. After that you can jump carrying the hat. edit: has changed
- edit: you can leave the hat in this area:


- Then again a monster robot. Tricky. My way was to throw the hat, run, pick it up and throw again and again all the time pushing the 'shift'-key. You don't have to bring it outside the tunnel, it's enough to get it close to the last gate. edit: you can run through now



Lambda Core:
- Getting up the platforms was surprisingly hard. The hat separates from you when entering the portal and takes its own way. It is possible though. I got it going into the portal in a slight rotation. When the hat stays on the platform - provided you followed it - you grab it and once you have it, you crouch. On second and third level there are pipes which can push you down, so stay down.
- Saving was frustrating for me. When I got up a platform and saved, after loading I fell down and died. What worked, was jump and save while midair. You have to move to the foremost end the platform and jump.
edit: has changed: sometimes you keep the hat after passing a portal, saving is fine now
- In the last stage, I did not fight. I just ran clockwise. While carrying the hat you cannot run, so I placed the hat in the first corner on the right behind the steps seen from the entry, Then I placed the sachel charges around the stairs, ran my way, pushed the button when the aliens spawned, took the hat an did a long jump . . .

edit: this doesn't work anymore, the hat and satchels don't stay in place due to the vibrations. But there are much fewer opponents now, so simply running and jumping into the portal worked fine.

Xen

On arrival in Xen the hat is gone. You will find it after jumping the floating rocks, the first teleporter and the energy cristal in a cave behind a dead scientist.





I found the Hivehand the optimal weapon for Xen and Gonarch's Lair, works fine against zombies, barnacles, ichthyosaurs, exploding houndeyes, bullsquids and trees, you can literally shoot around the corner. Not so good against houndeyes, headcrabs and Gonarch.

After coming out the first research station you can leave the hat where the two trees are, clear the area, up to the hole in the cave and come for it later.

During the big puzzle with the three leaves to open you can leave the hat at the healing pool.

In the next area where you see eight protozoans you can leave the hat at the beginning after the jump and clear the area all the way up the teleporters to the creek in the cave.

During the whole section where you build up the teleporter you can leave the hat in the control room.


Gonarch's Lair

After the teleporting you find the hat in front of you.

Exept for the cave where the water rises (you can leave it in the water for most of the time) you just rush through and stop only to kill some creatures for most of the chapter.

The final fight might be frustrating. In my first run I left the hat at the ammo canister where it still was after Gonarch fell down. Later I tried to place it in different places but the hat always disappeared. When finally the hat fell to the lower level and could be picked up later it was again placed at the ammo canister. So it seems to be a good spot. You might want so save from time to time when the hat is still where you put it.


Interloper

In Interloper the hat is easily blown away by exploding barrels, Vortigaunt attacs and those trampoline plants. So don't leave the hat in proximity of the trampolines. Healing showers are a good spot to place it.

During the first fight in the Vortigaunt village leave the hat in the house.

In the section where you have to solve the four plug-and-socket puzzles and during the following fight you can leave the hat in the shower.

For the next fight (in the room that you are sucked into and have to solve another puzzle of plugs and sockets) I left the hat in the small cave where you later have to shoot the second balloon-like thing. The room below the floor should also be fine.

In the room with the lasers you can leave the hat in the corner at the beginning.

In the section where you jump off a wall and encouter many Alien Grunts I just ran past them to the healing shower, put the hat down and shot them from inside the shower.

In the spot with the first Gluon rechargers I placed the hat in a corner in the lower part of the place, stayed close, ran up only to recharge the gun and shoot some controllers and as soon as I heard the door open I grabbed the hat and ran past the Grunts. I took two of them from above and ignored the last one I could not see at the moment.

During your ascent in the Grunt factory (the cubes on the conveyor belts) you open several portals. You can leave the hat at the portal where the three bullsquids are (and the ichthyosaurs in the water). This is the last portal connected:


As soon as you open it you can jump down (you won't land in the water) and teleport up with the hat.

After the cube you were on was examined by lasers three times you come to a section with controllers. You can take them out if you are quick enough but I just ran through to the next safe room and took the pain.

Directly after this room are the conveyors where you have have to shoot the red balloons to deactivate the force fields. I found it impossible to get through with the hat. So I left the hat in the far corner at the red force field ran as hell and shot the balloons without changing the line until the safe room. Then turned around, ran back, shot the Grunts in the way and ignored the rest. Took the hat and ran back again.

In the section where you disable the force fields for the trampoline jumps you open several portals, the last one in the last Vortigaunt control room. The portal you can leave the hat at ist located in the area with the second shielded controller and three Alien Grunts.


While disabling the three force fields you can leave the hat somewhere where it won't be blown away.

After the last jump you stand before a grate in a ventilation duct. You are sucked away as soon as you break it. Almost all weapons and the crowbar are too fast to grab the hat. Grenades didn't work, although with the right timing it should be possible. What worked was the Hivehand. It left me enough time to grasp the hat. A tripmine seems to work to.
The same problem at the next grate. A satchel charge was fine.


The tower

In the tower I held the hat in my hands and walked circles around the column. It didn't even hurt much.

In the areas where you have to get out to take out the controllers and deactivate the lasers I left the hat in the central area and stayed away from it as far as possible. Saved from time to time when I saw it was still there.

The last fight was tricky. The hat gets blown away easily. Walking or running circles didn't work. The controllers don't seem to affect the hat very much while the exploding barrels do.
I placed the hat directly at the column, walked on the other side, stayed there and did my best. Tried not to let one exploding barrel through. After several successful tries when the elevator went up I saw the hat was gone. So I saved in about half the fight, continued, after reloading checked if the hat was still there and began anew. Finally the elevator started moving, the hat was still there so I took it and walked my circles until the controllers were out of sight.
Except for the last Gonarch fight this was the most time consuming part of the achievement.


Nihilath



This was the last sight of the hat in my possession.

After teleporting I had no hat and no achievement either. I searched the whole area and looked in every corner but no hat anywhere. After a while I found this big baby quite disturbing and decided to look under it. Just before I had it out of the way I was teleported again and then a man came wearing my hat. And then the achievement popped up.

You find the Pizza in Questionable Ethics:




The playthrough ist basically the same as with the hat.




There are some differences between the hat and the pizza box:

- The pizza seems heavier.

- Sometimes it bends the laws of physics.

- The pizza sinks in the water or floats in various depths which can make it more difficult to find.

- The pizza box is bigger. It is easier to touch a wall or whatever when jumping which might change your trajectory.

- Ladders really suck
This ladder and the last one leading to the lambda complex I found impossible to get up with the box so I threw it up and shot it to the top.






- In teleporters you mostly end up standing on the box unable to move or jump. What helps is to hit the box with your crowbar until in moves.

- Pizza makes friends.




Good luck.