def.ps

 %!
 /square50 {setrgbcolor moveto 
            50 0 rlineto 0 50 rlineto -50 0 rlineto 
            closepath fill} def
 050 500 1 1.0 0 square50
 100 500 1 0.9 0 square50
 150 500 1 0.8 0 square50
 200 500 1 0.7 0 square50
 250 500 1 0.6 0 square50
 300 500 1 0.5 0 square50
 350 500 1 0.4 0 square50
 400 500 1 0.3 0 square50
 450 500 1 0.2 0 square50
 500 500 1 0.1 0 square50
 showpage