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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. You can take some laser damage to travel into the future. Once in the future, rearrange portals without affecting the present. Position them so the laser goes directly into the target to exit the chamber.

Test Chamber 14: First, travel to the present using 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 use the reflector cube to direct it into the next two nodes. 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. Ensure the reflector cube in the present hits all three nodes, adjusting as necessary. If you moved the future reflector cube, return to the future to bring it back to the present. Finally, place 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. Shoot a portal where the laser hits the wall and place a time portal on the opposite wall. Travel through the time portal to reach the future, bypassing the particle field. Head 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 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 shoot 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 cube on the lip above the second receiver. Travel to the future. Retrieve the future reflector cube and bring it back to the present by placing a time portal in the laser room. Position the cube to reflect the laser into the second receiver through the node. To reach the other side of the particle field without passing through it, use an existing portal or a time portal. Once in the present on the other side, 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.