You need to double everything. And use layout the size of the resolution. Create two virtual screens on one layout, each height or with of half of the screen ( depending if you want to split it vertically of horizontally ). Create two players, and create two... lets call them shadows. You'll need two arrays, one per player. Also you will need to create some sort of virtual position checker, which will be checking relative position of each player in regards to their own virtual rooms. So lets say each room would have one sprite at the end of it that you can check relative position of the players. Ok, now, you will have to take players one relative position, and use it to set position of his shadow in another player part of the screen every tick.
Ok, so we got all that, but now here's the biggest trick = you players stay in one place - they do not move! However everything else including shadows has got movement behavior with custom controls. Those controls are set in reverse, so when player hits right arrow, the whole level moves to the left.
Hope that will help!