beginfig(1);
path p; 
nbor := (sqrt(5)+1)/2 ; 
psi := 137.5 ; 
iter := 1000 ; 
c := 5 ; 
r := 0; 
for i=iter downto 0: 
 t := sqrt(i) ; 
 r := (r + psi) mod 360; 
 cv:= cosd((i/iter)*90); 
 p := ((0,0)--(t,1)--(t+1,0)--(t,-1)-- cycle) rotated r; 
 fill p scaled c withcolor (1,cv,0); 
 draw p scaled c; 
endfor;
endfig;
end