Entry Point

Test Chamber 13: Place portals as shown to redirect the laser sideways. Use a time portal to move the laser into the future. Enter the time portal to advance. Rearrange portals in the future to direct the laser into the target, then exit through the door.

Test Chamber 14: Travel to the present via a time portal. Summon a reflector cube and position it to redirect the laser through the first node. Use a portal to bring the laser through this node and reflect it into the next two. Travel to the future. Use portals to bring a laser into the present through the time portal, ensuring it passes through the node. Retrieve the reflector cube from the future and bring it to the present. Position the present reflector cube to hit all three nodes. If necessary, return to the future to retrieve the future reflector cube again and bring it to the present. Finally, position the future reflector cube to reflect the laser into the receiver, completing the chamber.

Test Chamber 15: Enter the particle field and place a portal where the laser hits the wall. Place a time portal on the opposite wall. Travel through the time portal to the future to bypass the particle field. Move to the other side of the room and use another time portal to return to the present, now on the far side of the particle field. Place a new portal on the upper wall so the laser hits the first receiver. Travel to the future and place a portal in the laser room to direct the laser to the receiver. Return to the present. The laser should now power an elevating platform. Stand on the platform and place a time portal behind the node to raise it. Summon a reflector cube and place it on the lip above the second receiver. Travel to the future. Retrieve the future reflector cube and bring it to the present using a time portal in the laser room. Position the reflector cube to direct the laser to the second receiver through the node. To bypass the particle field again, use a portal on the other side or a time portal. Reach the present on the other side of the particle field. Climb the stairs and use a portal on the upper wall to hit the third receiver. Place the reflector cube on the switch to complete the chamber.