                 GRID SCROLL TEST

A grid is scrolled vertically, horizontally and
diagonally which can be used to test linearity of
the display or video processor; and how it copes
with scrolling and framerate.

Button $Y can be used to switch between horizontal
and vertical, while the d-pad regulates speed. 

Diagonal scroll can be enabled with the $R button.

Button $A stops the scroll and button $X changes
direction. 
