Off To The Black Market

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 damage from the laser 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 complete the chamber.

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 direct a laser through the first node and then reflect 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 via a time portal. Ensure the present reflector cube hits all three nodes; adjust as needed. Travel back to the future to retrieve the future reflector cube if you moved it. Position the future reflector cube at the end of the nodes to reflect the laser into the receiver, completing the chamber.

Test Chamber 15: Start by going 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 the future to bypass 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 field. Place a new portal on the upper wall above the laser room 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; the laser should be powering an elevating platform. Stand on it 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 via a time portal placed within the laser room. Position it to reflect the laser through the node to the second receiver. To reach the other side of the particle field without going through it, use an existing portal or a 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.