As soon as you enter the test chamber, drop a portal right in the middle of the blue gel puddle and then another one on the floor near the plunger (below the blue 'X' on the wall). Coat the floor (by moving the portal) and then jump up to the button and hit it.
Welcome back to Aperture Science, a world where your Companion Cube isn't you're only company. Take control of Chell once again in Valve's sequel which takes you on an humorous and puzzling adventure and in our detail-packed guide we'll show you:
How to solve every test chamber first time.
Conquer every co-op chamber with a friend.
Loads of High Definition screenshots and videos showing you the solutions to every single chamber.
High Definition strategy videos for every achievement in the game.
Uncover all of the hidden secrets and Easter eggs.