Beat two Portal advanced maps.
Beat four Portal advanced maps.
Beat all six Portal advanced maps.
Complete Portal.
Detach security cameras from the walls.
Make the correct party escort submission position decision.
Earn bronze medals on all Portal challenges.
Earn gold medals on all Portal challenges.
Earn silver medals on all Portal challenges.
Acquire the fully powered Aperture Science Handheld Portal Device.
Knock down a turret with another turret.
Fall 30,000 feet.
Do whatever it takes to survive.
Jump 300 feet.
..?
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