Go To The Beginning

Test Chamber 13: Place portals as shown in the image to redirect the laser. Use a time portal to move the laser into the future. Enter the time portal yourself, even if it means taking some damage. In the future, rearrange portals so the laser hits the target. Enter the now-open door.

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 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. Position this cube to reflect the laser into all three nodes. If needed, return to the future to retrieve the cube again. Finally, place the future reflector cube to direct the laser into the receiver, completing the chamber.

Test Chamber 15: Start by passing 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 other side of the particle field in the future, where the field is inactive. Return to the present using another time portal to be on the correct side. Place a new portal on the upper wall to direct the laser to the first receiver. Travel to the future and place a portal on the small wall in the laser room to hit the receiver. Return to the present. An elevating platform near the switch will power up. Stand on it and place a time portal behind the node to raise the platform further. This allows 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 through the node and into the second receiver. To reach the other side of the particle field without going through it, use a portal or a time portal. Once in the present on the other side, climb the stairs and place a portal on the upper wall to hit the third receiver. Finally, move the reflector cube onto the switch to complete the test chamber.