On To Rahman

Test Chamber 13: Place portals as shown in the image. Use a portal to move the laser sideways and a time portal to move it into the future. You can take some damage to travel into the future. Once in the future, rearrange portals so the laser goes directly into the target.

Test Chamber 14: Travel to the present via a time portal. Summon a reflector cube and position it in the present as shown. Use a portal to bring a laser through the first node, then 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 goes through the node. Bring the future reflector cube to the present. Adjust the present reflector cube to hit all three nodes. Travel back to the future to retrieve the future reflector cube if needed. Place the future reflector cube at the end of the nodes to reflect the laser into the receiver.

Test Chamber 15: Go through the particle field to the left. Place a portal where the laser hits the wall and a time portal on the other wall. Travel through the time portal to the future to bypass the particle field. Return to the present on the other side. Place a portal on the upper wall to hit the first receiver. Travel to the future and place a portal on the small wall in the laser room to shoot the receiver. Return to the present. An elevating platform will power up. Stand on it and shoot a time portal behind the node to raise the platform further, allowing you to summon a reflector cube. Place this cube on the lip above the second receiver. Travel to the future. Pick up the future reflector cube and bring it to the present via another time portal in the laser room. Position it to reflect the laser into the second receiver through the node. To get to the other side of the particle field, use a portal or time portal. In 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. Finally, move the reflector cube onto the switch to complete the chamber.