Complete Interloper without taking any laser damage.
Accept G-Man’s offer of employment.
Decline G-Man’s offer of employment.
Defeat Nihilanth in under 4 minutes.
Take out all three Healing Crystals in Nihilanth’s Chamber at the same time.
Kill all Protozoans in the Borderworld.
Don't kill any Vortigaunts in the Borderworld.
Escape the Gargantua’s Lair without taking any damage from Gargantuas.
Kill a Controller without killing any of its mind-controlled Vortigaunt slaves.
Find each member of the missing research teams.
Get whacked into oblivion in the ledge fight.
Kill an Ichthyosaur with either the Tau or Gluon.
Skip the opening Xen island with a secret jump.
Drown in Lambda Core's coolant.
Use an entire clip of Gluon ammo in one continuous shot.
Escape the Hangar in Surface Tension without alerting the Soldiers.
Kill 20 Enemies with the Hivehand.
Kill 10 Enemies with Snarks.
Conduct all of the questionable research experiments.
Overcharge it anyway.
Get killed by your own Snarks.
Kill an Assassin with the .357 Magnum.
Headshot 20 Enemies with the .357 Magnum.
Kill 10 Enemies with Tripmines.
Kill a Barnacle with a Satchel.
Help the Barnacle and Headcrab find true love.
Kill 10 airborne Headcrabs using the Shotgun.
Kill a Marine with their own Grenade.
Kill 10 enemies with a reprogrammed Sentry.
Assemble all the possible Scientists and Guards at the end of Office Complex.
Use the alternate path in Office Complex.
Cook a Grenade for too long.
Kill 5 Enemies with one Grenade.
Kill a Headcrab using fire.
Get overtaken by a Headcrab's ample anterior.
Refuse to insert the specimen into the Anti-Mass Spectrometer.
Die in the AMS Beam before starting the experiment.
Pass the toilet paper to the Scientist in need.
Perform surgical caffeine extraction from 20 vending machines.
Ruin the microwave casserole.
Interfere with the alarm and laptop in Anomalous Materials.
Send the Hidden Hat to Xen.
Deliver the finishing blow to Gonarch with your Crowbar.
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