It's a 16x16 screen world which wraps around, if you move to the left or right you should eventually land on a non-empty screen. The "world" is anything but finished, to be honest, it's more of a debug / feature test world than anything else at the moment :)

Here's a picture of the whole world for reference: https://dl.dropboxusercontent.com/u/2332843/tuff.map.png