Reflector Cube

Test Chamber 13: Place portals as shown in the image. Use a portal to move the laser sideways and a time portal to send it into the future. Travel through the time portal. Rearrange portals in the future so the laser hits the target. Exit through the door.

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

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 opposite wall. Travel through the time portal to reach the future, bypassing the particle field. Move to the other side of the room and use another time portal to return to the present, now on the other side of the particle field. Place a new portal on the upper wall to direct the laser to the first receiver. Travel back to the future and place a portal on the small wall in the laser room to aim at the receiver. Return to the present; the laser should be hitting the first receiver, powering an elevating platform. Stand on the platform and place a time portal behind the node to raise the platform further, allowing you to summon a reflector cube. Place this reflector cube on the lip above the second receiver. Travel to the future. Retrieve the future reflector cube and bring it back to the present using a time portal in the laser room. Position it to reflect the laser into the second receiver through the node. Now, get to the other side of the particle field in the present. Climb the stairs and use a portal on the upper wall to hit the third receiver. Move the reflector cube onto the switch to complete the chamber.