Virtual Height/ Width

Ah yeah, the default for 8 direction movement is arrow keys. I didn't bother to do anything to adjust it.

I still don't quite understand what virtual width/height are used for. What kind of potential applications do they have?

Infinite scrolling. Jeff has an example I believe. It's just used for internal things like wrap around play area and object leaves/enters frame area.

Just to add to LB's answer. This is from the help file:

Virtual Width
Very useful for huge scrolling games: defines the virtual width of the frame. A large virtual width allows you to scroll on a large surface, larger than the frame itself. If the Wrap option is selected in a layer, the background of this layer will wrap automatically when it reaches the real width of the frame. For example, a frame size of 640x480 and a virtual width of 10000 will enable the player to scroll up to the position 10000 on the right without being stopped. If you enter -1 in this field the scrolling is quasi-infinite.

Virtual Height
Same as above, vertically.

Marv

I see... Infinite scrolling as in repeating/looping levels? I had always achieved this using the layer object instead of moving the camera, and having the layer set to wrap.