Testchamber 18: Advanced

if your speaking about the room full of turrets, with water underneath, im in the same spot, and i honestly have no clue. =/

Dead indeed Surprising for such a popular game.
For future generations stuck on this room, here's what to do:
- Get the vaporising fireball thing into the switch with portals on the left-hand wall (when it turns that way) and the very distant wall facing it; then quickly use portals to hit the switch on the pillar and open the gate.
- Kill the turrets by sending the vaporising fireball thing through portals aimed at each one.
- Hop on the "un-stationary scaffold" (lol) and ride it to the lower of the two alcoves on the far side. Hit the switch to open the door to the previous room and use portals to get back quickly.
- Go back to where the floor switch was and shoot a portal on the platform below, then return to the door, open it and shoot a portal on it from the other side while it is diagonal. Leg it back to your previous portal and jump into it from height: you'll shoot out and hopefully land in the alcove with the cube.