I don't know if this applies to all of the maps, but if you look at the chalkboard when you beat a map, you can see sentences. One of them is The cake is a LIE!
Guys, I think the quick match IS multiplayer, because I've seen people in gaming clans on there. Also, one time i was playing a one on one quick match with iceguns only and i finally convinced him to stop shooting me and paint the walls with bullet holes.
On level nine you have to put a portal on the left wall ON THE TOP and one on the ground. go through the ground one and you should fall back into it and get thrown over the pillar thingy.
 "UMAG"){kind=icon}
 "Sentry Fortress"){kind=icon}
 "You Have To Burn The Rope"){kind=icon}
 "TETRIS'D: The Game"){kind=icon}
 "Portal: The Flash Version"){kind=icon}
 "xD Press xD"){kind=icon}
 "Enough Plumbers"){kind=icon}
 "Raze"){kind=icon}
 "the Game of Disorientation"){kind=icon}
 "Storm the House 3"){kind=icon}
 "GunMaster Onslaught 2.0"){kind=icon}