Accomplish the indicated achievement to get the corresponding number of Gamerscore points:

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