% --- start of displayed preamble in the book ---
% --- end of displayed preamble in the book ---
defaultfont:="ptmr8r";
warningcheck:=0;
beginfig(1)
pickup pencircle scaled 4pt
yscaled .2pt rotated 60;
n:=4;
for i := (n*20) step -(n) until (n):
c:=((n*20)-i)/(n*2);
draw (i,0)..(0,i)..(-i,0)
..(0,-(i-n))..(i-n,0)
withcolor ((100-i)/100,i/100,0);
endfor
endfig;
end;
