The starting point of the player in each file/folder is either below or above the "terrain". I bet it's set constant, and the grid is just there where the function creates it. Thus it's either "ceiling" or "ground". I'd suggest placing player above his z-point on entry, perhaps leaving (x,y) the same?
And yes, lines or minimap would be nice. It's pretty hard to explore with only accelerometer on hand .
The maximize button ain't workin', hence the size...
@EDIT: Also, what happens if I manage to enter an empty file/folder? A flat plato?