Black Mesa

Kill a Controller without killing any of its mind-controlled Vortigaunt slaves.

Escape the Gargantua’s Lair without taking any damage from Gargantuas.

Pass the toilet paper to the Scientist in need.

Perform surgical caffeine extraction from 20 vending machines.

Kill 10 airborne Headcrabs using the Shotgun.

Kill 20 Enemies with the Hivehand.

Ruin the microwave casserole.

Kill an Assassin with the .357 Magnum.

Kill 10 enemies with a reprogrammed Sentry.

Deliver the finishing blow to Gonarch with your Crowbar.

Conduct all of the questionable research experiments.

Kill 10 Enemies with Snarks.

Get whacked into oblivion in the ledge fight.

Headshot 20 Enemies with the .357 Magnum.

Drown in Lambda Core's coolant.

Kill a Headcrab using fire.

Kill a Marine with their own Grenade.

Complete Interloper without taking any laser damage.

Defeat Nihilanth in under 4 minutes.​

Die in the AMS Beam before starting the experiment.

Accept G-Man’s offer of employment.

Kill 5 Enemies with one Grenade.

Kill an Ichthyosaur with either the Tau or Gluon.

Kill 10 Enemies with Tripmines​​.

Skip the opening Xen island with a secret jump.​

Assemble all the possible Scientists and Guards at the end of Office Complex.

Use the alternate path in Office Complex.

Don't kill any Vortigaunts in the Borderworld.

Find each member of the missing research teams.

Use an entire clip of Gluon ammo in one continuous shot.

Kill all Protozoans in the Borderworld.

Get overtaken by a Headcrab's ample anterior.

Interfere with the alarm and laptop in Anomalous Materials.

Overcharge it anyway.

Send the Hidden Hat to Xen.

Decline G-Man’s offer of employment.

Kill a Barnacle with a Satchel.

Refuse to insert the specimen into the Anti-Mass Spectrometer.

Take out all three Healing Crystals in Nihilanth’s Chamber at the same time​.

Escape the Hangar in Surface Tension without alerting the Soldiers.

Help the Barnacle and Headcrab find true love.

Get killed by your own Snarks.

Cook a Grenade for too long.