Jump to tips on the hat/pizza achievements
Black Mesa Inbound > Anomalous Materials > Unforeseen Consequences > Office Complex > "We've Got Hostiles" > Blast Pit > Power Up > On A Rail > Apprehension > Residue Processing > Questionable Ethics > Surface Tension > "Forget About Freeman!" > Lambda Core > Xen > Gonarch's Lair > Interloper > Nihilanth > End Game > Credits.
|Pepperoni Precipitation||Questionable Ethics → Endgame||View the *other* secret ending.||carry the pizza from Questionable Ethics cafeteria to the Nihilanth|
|Rare Specimen||Unforeseen Consequences → Lambda Core||Send the Hidden Hat to Xen.||near entrance to Sector C|
|The Rarest Specimen||Unforeseen Consequences → Endgame||Carry the Hidden Hat to Endgame.||all the way to the Nihilanth|
|Futile Resistance||Questionable Ethics →||Kill 10 enemies with Snarks.|
|Ethically Questionable||Questionable Ethics||Conduct all of the questionable research experiments.||kill alien grunt (in the green liquid chamber), bullsquid (with tesla discharge), snarks (fire them until it breaks), headcrabs (use cyanogen gas against the ones in the Xen terrarium, and also shoot them with the superlaser in the tau cannon area)|
|Universal Gravitation||Questionable Ethics →||Get killed by your own Snarks.|
|One Step Ahead||Power Up →||Kill 10 Enemies with Tripmines.|
|Unified Coupling Theorum||Unforeseen Consequences →||Help the Barnacle and Headcrab find true love.||supposedly easiest on the conveyor belt in We've Got Hostiles, but the tree map part of Xen was easiest for me|
|Kinetic Repulsion||We've Got Hostiles →||Kill a Marine with their own grenade.|
|Digital Wizardry||We've Got Hostiles →||Kill 10 enemies with a reprogrammed Sentry.|
|Well-Done||Unforeseen Consequences →||Cook a grenade for too long.||right-click (alt fire), hold it|
|Our Brains And Your Brawn||Office Complex||Assemble all the possible Scientists and Guards at the end of Office Complex.||gather four guards (including the one near the start) and one male and one female scientist to the elevator shaft at the end|
|Prophylactic Suggested||Unforeseen Consequences →||Get overtaken by a Headcrab's ample anterior.||just let a headcrab kill you|
|Anti-Matter Over Mind||Interloper||Kill a Controller without killing any of its mind-controlled Vortigaunt slaves.|
|Black Mesa Decathlon Winner||Interloper||Escape the Gargantua's Lair without taking any damage from Gargantuas.||cannot take any damage from gargantuas in the whole map, cannot load saves in the map, have to load from the previous map|
|Brownian Motion||Anomalous Materials||Pass the toilet paper to the scientist in need.|
|Caffeine Extraction||Anomalous Materials →||Perform surgical caffeine extraction from 20 machines.||cause damage to a vending machine and recover health from the soda cans|
|Calculated Trajectory||Office Complex →||Kill 10 Airborne Headcrabs using the Shotgun.|
|Centripetal Attraction||Surface Tension →||Kill 20 enemies with the Hivehand.|
|Contest Propellant||Interloper||Find the snack supply canister.||in a room hidden behind wicker crates after the first battle against alien controllers in Interloper, right before an elevator|
|Convection Refinement||Anomalous Materials||Ruin the microwave casserole.|
|Dead Reckoning||Apprehension, Lambda Core||Kill an Assassin with the .357 Magnum.|
|Doctor's Signature||Gonarch's Lair||Deliver the finishing blow to Gonarch with your Crowbar.|
|Following the Rules||Xen||Use the welcome mat.||start of tent laboratories on Xen: crouch on it or use the interact key|
|Gonad Glider||Gonarch's Lair||Get whacked into oblivion in the ledge fight.|
|Gray Matter Propulsion||Blast Pit →||Headshot 20 enemies with the .357 Magnum.|
|Hyper Saturation Conundrum||Lambda Core||Drown in Lambda Core's coolant.|
|Inflammatory Actions||Unforeseen Consequences →||Kill a Headcrab using fire.||use a flare, don't cause any other damage|
|Laser Immunization||Interloper||Complete Interloper without taking any laser damage.||red lightning in the grunt factory counts as a laser, and green poison goo might count as one too|
|Late for Work||Nihilanth||Defeat Nihilanth in under 4 minutes.|
|Less Than Desirable Consequences||Anomalous Materials||Die in the AMS Beam before starting the experiment.|
|Limitless Potential||Endgame||Accept G-Man's offer of employment.|
|Mega Hertz||Unforeseen Consequences →||Kill 5 enemies with one grenade.||easiest on some stacks of barnacles|
|Nuclear Fishin'||Surface Tension →||Kill an Ichthyosaur with either the Tau or Gluon.|
|Orbital Trajectory||Xen||Skip the opening Xen island with a secret jump.|
|Permeable Infrastructure||Office Complex||Use the alternate path in Office Complex.||in the rather open office area divided with dividers into cubicles (not separate rooms) with meeting rooms all around, where you battle vortigaunts; there's a meeting room with couches that has a short ladder drop down from the ceiling.|
|PhD in Pacifism||Interloper||Don't kill any Vortigaunts in the Borderworld.||includes vorts controlled by controllers|
|Post-Mortem Interval||Gonarch's Lair||Find each member of the missing research teams.||press use (E) on each of them, or crouch|
|Premature Expulsion||Lambda Core →||Use an entire clip of Gluon ammo in one continuous shot.|
|Prolific Popper||Xen → Interloper||Kill all Protozoans in the Borderworld.||achi needs 64 killed. 37 in Xen, 22 in Gonarch's Lair (one requires the cyanogen canister), 8 at the end of Interloper, so 67 available.|
|Proverbial Tinkerer||Anomalous Materials||Interfere with the alarm and laptop in Anomalous Materials.||the alarm is under the circular reception desk right at the very start of the level|
|Quantum Capacitance||Questionable Ethics →||Overcharge it anyway.||(The Tau Cannon.)|
|Rather an Anticlimax||Endgame||Decline G-Man's offer of employment.|
|Remote Detonation||Blast Pit →||Kill a Barnacle with a Satchel.|
|Resonance Procrastinator||Anomalous Materials||Refuse to insert the specimen into the Anti-Mass Spectrometer.|
|Specimen GG||Nihilanth||Take out all three Healing Crystals in Nihilanth's Chamber at the same time.||using satchel charges|
|Stealth Technology||Surface Tension||Escape the Hangar in Surface Tension without alerting the Soldiers.||follow the dude, quicksave before trying|
|The Plan||Xen → Gonarch's Lair||Use Cyanogen to kill Gonarch.||cyanogen picked up towards the end of the laboratories on Xen; it's bright yellow and has a warning label on it reading "compressed cyanogen chloride"|
|Unquestionably Ethical||Xen → Gonarch's Lair||Don't use the Cyanogen and let the Gonarch live.||the room with the cyanogen injector is high up and you can jump to a ledge and avoid the fight|
|xen when||Lambda Core||Wait too long to jump into the Lambda Teleporter.||one minute after it opens|
Interloper, village, gargantuas' lair, plug puzzle area: lots of running, hold onto it. in the gargantuas' lair section, quicksave right after the final jump and before the jump pads: it's possible for the hat to glitch out in the jump pads and be thrown up into the air.
in the alien grunt factory, be careful with sucking air tubes: keep the hat in front of you, because it's possible for it to get stuck on the outside and be left behind. if carrying the pizza, quicksave before every vent, because the pizza will easily get stuck outside the vent or in a corner. in the cable-and-plug-and-pump puzzle room, the hat can either be left in the center while you solve the puzzles, or you can solve the puzzles and take it with you; the hat is annoying and rolls away so i'd leave it in a safe spot until at least after the controller battle, but the pizza is nice and flat so i'd carry it along.
Interloper, conveyor belt area: in the conveyor belt battle against alien controllers the hat can be safely left in the starting area (between the red and blue gates) while you go and clear a path and kill the controllers; you can then walk back against the conveyor belt and pick the hat up again.
towards the top of the alien grunt factory, in the huge puzzle chamber that involves shooting the red tumor things that control the red wires that control the gates, the hat is very unstable: it'll bounce around on its own, probably into the abyss below, so as tempting as it is to leave the hat by a jump pad or teleporter or healing pod, i suggest bringing it along with you.
if you don't want to bring the hat with you, leave it in the healing pod: it'll still bounce but it's somewhat restricted (but not impossible that it'll escape).
the pizza seems to be much more stable, and doesn't need to be carried through all puzzles.
(the three paths in the three-wire puzzle: left - couple of shielded controllers throwing balls, middle - shielded controllers and vortigaunts, right - many many controllers.)
quicksave after the red wire puzzle and before the final jump upwards, in case you lose grip of the hat or pizza.
Interloper, end of the factory: after the ring of 8 jump pads at the top of the alien grunt factory (incidentally the trigger point for the Laser Immunization and PhD in Pacifism achievements), you'll be dumped into a pit of dead alien grunts. do not shoot the grating barring the air vent: it'll immediately suck you and you won't have time to grab the hat or pizza. use a well-timed grenade instead: count to three and lob it at the top of the grating, so it'll explode close enough to it. you'll have a tiny amount of time to grab the hat, but it's enough. (the hivehand works too, since its bullets are slow.)
if carrying the pizza, this vent is particularly troubling, since it'll get so easily stuck outside it while you're stuck in; what i did was i threw in the pizza, then threw in most of my grenades, and with luck it ended up falling down all the way and i could pick it up after fighting the first controller.
in general it's safe to leave the hat on the moving platforms (don't need to carry it all the time); try to keep it upright, but this isn't mandatory. keep an eye on it once in a while, because controllers' energy balls' and exploding barrels' splash damage will easily throw it off the edge. the pizza is much easier in this regard, since it doesn't roll. you have to bring the hat with you to the off-elevator battles though. focus on shooting down the exploding barrels: they're signalled by a metallic ringing-sort of qui-uh-uh-uh sound.
in the first off-elevator battle (grunts and shielded controllers, with shields easily destroyed) you need to keep track of where the hat is: it tends to roll and there's no edge. focus on the grunts, and watch out for the poison barrel generators.
in the second off-elevator battle (more shielded controllers, shield generators hidden) keep it in sight when you destroy one of the shields, then drop it in the center of the shield "bunker": it's safest there, since controllers' lightning balls will chuck it away otherwise, and there's much less floor.
in the final ascent portion focus on the barrels, they have more splash damage. once the lift starts moving again, grab the hat.
After Interloper's elevator battle you're home free. Heal up at the healing pool, carry it around the level, enter a lift, jump on a piston. The first teleporter is yellow and green, a regular Black Mesa teleporter: throw the hat in; if you just walk in holding it you won't find it on the other side, but if you throw it in you'll see a quick flash and then, when you enter it yourself, it'll be at your feet. Jump across some islands and you'll be at the Nihilanth's red teleporter. You can either throw the hat/pizza in or walk in holding it, it doesn't matter: you'll get the Rarest Specimen/Pepperoni Precipitation achievement once you kill the Nihilanth and meet the G-Man.
General notes for Pepperoni Precipitation: I'd say this is in general easier than The Rarest Specimen, for the main reason that the pizza is all flat edges while the hat rolls easily. It's not entirely easier, though: the pizza is much bigger than the hat, and for example many enclosed ladders are much harder, because you'll only fit in a certain angle or not fit at all, having to carry the pizza outside the ladder, or dropping it on your head and then crowbaring it above you. The pizza is also more difficult in Interloper's sucking air and water vents, because it'll easily get stuck and left behind, but this can happen with the hat also. With teleporters: like with carrying the hat, you'll need to walk into teleporters pizza-first, because otherwise it'll be left behind at the source. After teleportation the pizza will spawn at your feet (or rather, you'll spawn on top of it), and you'll be stuck for a moment: crowbar the pizza a bit and you'll be free.
I believe it's almost possible but actually impossible to do both the pizza achievement and hat achievement at once. Both items are very light for their size, and can't be thrown a long distance; the hat can be thrown further than the pizza, but a flare can be thrown further than the hat. There are two main reasons why I believe doing both at once is impossible: Gonarch's Lair (the gonarch is very powerful and will kill you if you stall by chucking both items along) and the air vents in Interloper. Maybe with speedrun-like strats its possible to do both while skipping most of the levels, but I'm doubtful.
On the other hand, it is possible to carry both the purple Hidden Hat and the cyanogen canister, which is used to skip the Gonarch boss fight. (It's also used for The Plan and Unquestionably Ethical, and required for part of Post-Mortem Interval). The cyanogen is very heavy and cannot be thrown far; it's also cylindrical and will roll away easily. There's a couple of very-difficult-to-reverse jumps in Xen, but they either can be reversed or both items can be brought along: in the underground one with the first red tree-root-wire opening a leaf you can crawl along part of the root backwards (it becomes non-clipping quite soon) and barely make a long jump back, and in the one after the tree map opening with a jump to an island with waterfalls and exploding houndeyes you can jump to a side island, throw the hat across (hence this might be impossible with the pizza), jump back, and then jump while holding the cyanogen. At the end of Xen simply throw the hat into the teleporter before jumping in while holding the cyanogen, and the hat and cyanogen will be waiting on the other side, resting on a rock. Carry both of them past the first fight against the Gonarch, and then, after blowing up your first wall, there's a teleporter that the cyanogen can be placed on – you only need to carry the hat after this.
Presumably it's also possible to carry both pizza and cyanogen, but I expect this'll be a bit harder, since the pizza can't be thrown as far as the hat. The battle against the Gonarch isn't that bad, and it's probably easier with the pizza since it doesn't roll around at all.
cl_drawhud 0; r_drawviewmodel 0
cl_drawhud 1; r_drawviewmodel 1
posted 2022-10-11, edited 2022-10-23, when i achieved the last of the achievements.
"i'm sticking to you like white on calcium" (scientist line) – does this make any sense?