GameSpot may get a commission from retail offers. Start by moving forward to the portal gun stand. The ground will break below you, causing you to fall into the waters below. Move forward up the short ...

It's here where you'll battle GLADOS to complete the game. At first there's nothing to do but stand around and listen to GLADOS taunt you. Eventually, a piece of the machine will drop out of GLADOS.

The fan-made modification to Portal 2, called Portal: Revolution, gained popularity shortly after it was released. With over 40 new test chambers, there are naturally some that players find difficult ...

Interact with the projector screen to raise it and reveal a set of buttons arranged in a grid. Selecting the correct buttons will open the nearby door. You can use the projector to determine the ...

Return to Aperture for further testing. Our Portal 2 Walkthrough provides a walkthrough for story mode, tips for co-op, and unlockables.