OBJECT:  The object of Double Cross is to avoid placing a line
on the screen which crosses, overlaps or backs over any of the
previously played white lines.  Players take turns laying down
lines in a chosen direction.  The directional keys are as follows:

Player 1:  Up =   W   Left =  A   Player 2:  Up =   I  Left =  J
           Down = Z   Right = S              Down = M  Right = K
         
NOTE: (1) To make things interesting the line length at each play
          is random within a narrow but noticeable range!
      (2) Bonus points are awarded for finding hidden crosses.