It really depend of what you want to achieve.
In ski play 0.4.0 the tile are randomly generated and expose at the bottom of the screen and they call a scrolling function by recursively calling it to swapping up to x,y-1 until y is under 0...
i change the variable that wait with a variable that changing the waited time.
In previous version i was emitting at each frame i wanted i use emit "upward" and swap the tile to up and make the previous position replace with a white tile.
Emit is calling all the tile of the screen so it wasn't optimal in device.
Before I was using emit function to much for scroll up all the tile and check all the tile
If you want a pure scrolling with predefined tile you might check/ask Orkn about his example available in Art8 Tile Hill
