I had previously played the Portal 2 campaign and DLC split screen on my PS3. I had recently started playing the custom single player maps on my PC (since the PS3 included a PC download voucher). I'm now trying to play the cooperative co-op maps split screen on either my PS3 or PC. From what I understand this won't happen on PS3.
On PC, I was able to use x360ce and play the co-op campaign again with a spare non-360 controller. However, when starting the co-op custom maps, I do not get presented with a "press x for the second controller" like I did with the campaign. Instead the game just starts to look for friends online. Is it possible to play co-op custom maps split screen? If so, how?