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There are 14 achievements in Portal worth a total of 175  on the Xbox 360 version.

Picture	Name	Description
	Lab Rat	Acquire the fully powered Aperture Science Handheld Portal Device.	5
	Fratricide	Do whatever it takes to survive.	5
	Partygoer	Make the correct party escort submission position decision.	5
	Heartbreaker	Complete Portal.	10
	Terminal Velocity	Fall 30,000 feet.	5
	Long Jump	Jump 300 feet.	5
	Cupcake	Beat two Portal advanced maps.	10
	Fruitcake	Beat four Portal advanced maps.	20
	Vanilla Crazy Cake	Beat all six Portal advanced maps.	30
	Basic Science	Earn bronze medals on all Portal challenges.	10
	Rocket Science	Earn silver medals on all Portal challenges.	20
	Aperture Science	Earn gold medals on all Portal challenges.	40
	Camera Shy	Detach security cameras from the walls.	5
	Friendly Fire	Knock down a turret with another turret.	5

[edit] Still Alive Achievements

The expanded Xbox Live Arcade release adds several new Achievements, worth a total of 200 .

Picture	Name	Description
	Go for the Gold	Win a gold medal on a challenge map	15
	Out of the Blue	Once you have control of both portals, only enter the orange portal.	25
	Rat's Tale	Find all the Rat Man Dens.	15
	Is Anyone There?	Complete the game without ever taking a bullet.	20
	Saw that one coming	Cause a rocket sentry to destroy its own rocket when the rocket has been redirected back towards it.	5
	The Camera Adds 10 Pounds	Knock a turret over with a security camera.	10
	Like a Rat	Trap yourself in a test chamber so that GLaDOS has to help you continue.	20
	Feeling like Floating	Dissolve a turret.	5
	Tests like Chicken	Find the chicken’s test results.	15
	Cupcake	Beat 5 advanced chambers.	10
	Fruitcake	Beat 10 advanced chambers.	25
	Vanilla Crazy Cake	Beat all advanced chambers.	35