Make a runway with the speed gel, and drop some blue gel from the white wall above the end. Jump down and run along the speed gel into a portal so you fling up to the button. Put a portal on the ground under the button for the door. Put the cube on the button and run up to the exit.
Keep doing that until you reach the cube, grab it and take it back to the start. Setup a runway of speed gel from the back wall over the ramp, and use that to jump the gap. New element, Orange Gel! this gel makes you move faster while moving on it. Now fling yourself again, but aimed for the exit elevator. Reunite with Glados (which activated a button). Get up high by the fan and fling yourself to the Control room with the ramps to the other side. You can jump to nearby pages of the game using the links above.
