Sp a1 intro4

sp_a1_intro4 is the fourth map in the Portal 2 singleplayer campaign, and the fourth map of the chapter The Courtesy Call.

Routes

This covers two chambers, and while the setup is easy to understand, it can be difficult to do quickly and efficiently. First of all, when jumping out of the elevator instead start wallstrafing on the left of the stairs, since the usual right taken by runners has moss with built-in collision detection blocking the way.

Now when entering, it is reccommended to use bunnyhopping to get to the pit before the cube falls in, thus allowing you to place a portal underneath where it would normally fall, which gives the cube enough momentum (if placed correctly) to land on the button. If you want to do this even quicker, start walking into the closed door so that you can start moving through the second it opens. Next, we're going to need to perform a glitch in Chamber 04 that will allow a quicker, alternate puzzle solution that opens the door to play out. Place a portal on the closest portalable surface close to the door and walk against it. When the orange portal opens, you should be through, where you can shoot a blue portal twice; Under the cube on the platform opposite you, and then at the upper right of the door. Now, go through the portal holding the cube and wedge it between the door and portal, such that it disappears from view entirely, but you are still holding it. (In reality, it is now on the other side of the door.) Drop it, and because the game thinks that you've managed to throw a cube in while the door was open, the Announcer will say a different line and the door will open for you.

To finish off the map, place a blue portal in front of you, go to the other side of it, and jump through as soon as the orange portal opens. If done right, you can skip time by jumping over the broken glass. Bunnyhop through to the elevator, and jump straight through, as if done right the announcer will have no quote that you have to wait for.

Links

https://www.youtube.com/watch?v=tcfJEeyERJc - Tutorial by Znernicus https://www.youtube.com/watch?v=5x1KXcvHfnQ - Portal 2 Segmented World Record (area by Isolitic)