This is the fortieth level of the game, and takes place within Aperture Science Enrichment Sphere #3. This level features Repulsion Gel, and introduces players to the ability of Gels to coat objects. This level also introduces Water and its ability to remove the effects of Gels from objects and surfaces. Goo is present in this level as its main hazard.
Go to the test area and fire a portal to the floor under the Repulsion Gel. Place the other portal in front of the Switch.
Wait for the gel to travel through and then place the portal on the wall on the left.
Jump from the gel to push the switch and then go under the waterpipe to wait for the gel to paint the floor.
As soon as the floor is painted, jump from the floor to the ledge above it.
Go to the left and through the door.
Place a portal on the area where the gel is dripping and the other portal to the angled wall.
Wait for the gel to paint the wall properly and then fire a portal above the beam higher up and the other one on the wall and then go through.
Shoot a portal to the angled wall and the other on the floor.
Jump through the portal on the floor and you should get to the exit.
Go up the stairs ahead and shoot a portal on the beam on the left-side further ahead.
Turn around to see a short catwalk. Go to the end of it and place the other portal on the floor under the gel.
Wait for the gel to paint the surface. Walk to the metal balcony facing the beams and fire the portal from the floor to the surface below.
Jump to go through the portal and you should get to the catwalk.
When facing the gel on the catwalk, walk to the left and put portals on the wall, one as high as you can and the other so you may enter through it.
Go along the catwalk and enter the testing area and fire portals to the floor under the gel and the other one below the cube.
Catch the bouncing cube. You may want to use the water to stop the cube.
If you managed to catch the cube without using the Water, wash the gel out of the cube.
Place the portals under the gel and the other one in front of the elevator. When the gel has entered through the portal, place the portal further away.
Jump to the elevator by using the gel, turn around and place the same portal above the cube.
The cube should bounce off the button and the elevator takes you up. Now turn to face the final elevator and go in the elevator.
