Brownian Motion
Pass the toilet paper to the Scientist in need.
Caffeine Extraction
Perform surgical caffeine extraction from 20 vending machines.
Calculated Trajectory
Kill 10 airborne Headcrabs using the Shotgun.
Centripetal Attraction
Kill 20 Enemies with the Hivehand.
Convection Refinement
Ruin the microwave casserole.
Dead Reckoning
Kill an Assassin with the .357 Magnum.
Digital Wizardry
Kill 10 enemies with a reprogrammed Sentry.
Ethically Questionable
Conduct all of the questionable research experiments.
Futile Resistance
Kill 10 Enemies with Snarks.
Gray Matter Propulsion
Headshot 20 Enemies with the .357 Magnum.
Hyper Saturation Conundrum
Drown in Lambda Core's coolant.
Inflammatory Actions
Kill a Headcrab using fire.
Kinetic Repulsion
Kill a Marine with their own Grenade.
Mega Hertz
Kill 5 Enemies with one Grenade.
Nuclear Fishin'
Kill an Ichthyosaur with either the Tau or Gluon.
Permeable Infrastructure
Use the alternate path in Office Complex.
Premature Expulsion
Use an entire clip of Gluon ammo in one continuous shot.
Prophylactic Suggested
Get overtaken by a Headcrab's ample anterior.
Proverbial Tinkerer
Interfere with the alarm and laptop in Anomalous Materials.
Quantum Capacitance
Overcharge it anyway.
Rare Specimen
Send the Hidden Hat to Xen.
Remote Detonation
Kill a Barnacle with a Satchel.
Resonance Procrastinator
Refuse to insert the specimen into the Anti-Mass Spectrometer.
Unified Coupling Theorum
Help the Barnacle and Headcrab find true love.
Universal Gravitation
Get killed by your own Snarks.
Prolific Popper
Kill all Protozoans in the Borderworld.
PhD in Pacifism
Don't kill any Vortigaunts in the Borderworld.
The Rarest Specimen
One Step Ahead
Kill 10 Enemies with Tripmines.
Stealth Technology
Escape the Hangar in Surface Tension without alerting the Soldiers.
xen when
Our Brains And Your Brawn
Assemble all the possible Scientists and Guards at the end of Office Complex.
Less Than Desirable Consequences
Die in the AMS Beam before starting the experiment.
Orbital Trajectory
Skip the opening Xen island with a secret jump.
Following the Rules
Doctor’s Signature
Deliver the finishing blow to Gonarch with your Crowbar.
Gonad Glider
Get whacked into oblivion in the ledge fight.
Post-Mortem Interval
Find each member of the missing research teams.
The Plan
Unquestionably Ethical
Contest Propellant
Laser Immunization
Complete Interloper without taking any laser damage.
Black Mesa Decathlon Winner
Escape the Gargantua’s Lair without taking any damage from Gargantuas.
Anti-Matter Over Mind
Kill a Controller without killing any of its mind-controlled Vortigaunt slaves.
Specimen GG
Take out all three Healing Crystals in Nihilanth’s Chamber at the same time.
Late for Work
Defeat Nihilanth in under 4 minutes.
Limitless Potential
Accept G-Man’s offer of employment.
Rather an Anticlimax
Decline G-Man’s offer of employment.
Pepperoni Precipitation
Well-Done
Cook a Grenade for too long.