what is the max size of a shape?

[Sarah Allen]

So, I've got a couple of 5th grade assistants-in-training  
experimenting with lessons for tomorrow's Shoes class #2.  They have  
been exploring boundaires and came up with this app:

Shoes.app do
    fill yellow
    stroke blue
    rect :left => 1, :top => 1, :width => 100000000
end
we were puzzled by the results (see image here: http://skitch.com/raptorx/bt8qe/shoes 
 ) which appear to create a really tiny box instead of a really big  
one.  I wondered whether there is some size limit or rollover  which  
causes this behavior.

Thanks,
Sarah