%!
/pageno 0 def

/page-begin {
/pageno pageno 1 add def
  gsave
  72 dup scale
  1 72 div setlinewidth
  /Times-Roman findfont
  0.2 scalefont
  setfont

  1 1 translate
} def

/page-end {
  0 0 moveto
    gsave
    1 1 1 setrgbcolor
    (Page ) show pageno (      ) cvs show
    grestore
  grestore
  showpage
} def

% g s = arguments to this procedure
% g entered first, s second
/fill-square { % the color shade g and the side s now sit on the stack
1 dict begin
% define s (local) to be the top value on the stack
/s exch def
% define g (local) to be the value now on the top of the stack
/g exch def
newpath
  0 0 moveto
  s 0 lineto
  s s lineto
  0 s lineto
  closepath
gsave
  g aload pop setrgbcolor
  fill
grestore
stroke
end } def

% =================================================

/s 0.5 def
/g [ 1 1 0 ] def

% === page 1 ==============================================

page-begin

gsave

10 {

g 1 fill-square

0.25 0.25 translate
  % decrease the red component of g
  g 0 
  g 0 get 0.1 sub 
  put
} repeat

grestore

0.5 0.5 moveto
(Squares and circles) show
page-end

% === page 2 ==============================================

page-begin

/g [ 1 0 1 ] def

gsave

10 {

g 1 fill-square

newpath
0 0 0.25 0 360 arc
gsave
g aload pop setrgbcolor
fill
grestore
stroke

0.25 0.25 translate
  g 0 
  g 0 get 0.1 sub 
  put
} repeat

grestore

page-end