Tunnel Boring Machine

Test Chamber 13: Place portals as shown in the image. Use a portal to redirect the laser sideways and a time portal to move it into the future. You may take some damage from the laser to advance into the future. Once in the future, rearrange portals without affecting the present. Position them so the laser hits the target directly, allowing you to proceed through the door.

Test Chamber 14: First, take a time portal to the present. Summon a reflector cube from the central switch and position it in the present as indicated. Use a portal to guide a laser through the first node, then use this to reflect the laser 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 designated 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 its position if necessary. You may need to return to the future to retrieve the future reflector cube if you moved it. Finally, position the future reflector cube at the end of the nodes in the future so it reflects the laser into the receiver, completing the chamber.

Test Chamber 15: Begin by passing through the particle field on the left. Place a portal where the laser strikes the wall and a time portal on the opposite wall. Travel through the time portal to reach the future, bypassing the particle field. Proceed 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 above the laser room so the laser hits 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 still be hitting the upper receiver, powering an elevating platform near the switch. Stand on this platform 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 via a time portal. Retrieve the future reflector cube and enter the laser room. Use a time portal within the laser room to bring the future reflector cube to the present. Position it to reflect the laser into the second receiver through the node. To reach the other side of the particle field without traversing it, use a portal on the other side or a time portal. You need to be 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. Move the reflector cube onto the switch to complete the test chamber.