Sp a1 intro2
sp_a1_intro2 is the second map in the Portal 2 singleplayer campaign, and the second map of the chapter The Courtesy Call.
At the beginning of the level, get out of the elevator and wallstrafe along either side of the railing to gain speed. This is a widely known way to gain speed at the beginning of most Portal 2 levels, however this is notably the first level this can be done in. Following this, bunnyhop down into the pit where the cube and button are. Following this, there are two routes that are generally taken when completing the level.
1) Attempt to solve the puzzle as fast as possible. This strategy is somewhat efficient, and is the route used by the majority of speedrunners. It is recommended to simply throw the cube through the portal onto the button when the portal for that is activated. As usual, bunnyhopping while doing all this is strongly recommended. Once done, go and stand just outside of the elevator and wait until the Announcer finishes the sentence "Please take a moment to write down the results of your test.", and then enter the elevator. This is done to reduce the time between the Announcer finishing one of his sentences and entering a load trigger in the elevator, since the Announcer MUST finish his quotes before a load trigger in the elevator can actually take effect. By waiting to enter an elevator so that a load trigger will be entered right after the pre-recorded messages finish, time can thus be saved in game.
2) Throw a cube above the testing area onto the button. Due to the fact that, as part of the facility's destruction, there are patches of the roof that have holes with no collision detection, a cube can be thrown through it in such a way that it flies above the level, and ends up re-entering the level just above where the button is, meaning that the portal to it never actually has to be opened. While this saves a lot of time in a speedrun, it is extremely difficult to succeed in throwing it above the level, and in most cases will end up stuck on the roof in an area where collision detection still applies downwards. When finishing the level, the same elevator entry is used as described in the other route.