ancho = 640 : alto = 480
open window 640,480
backcolor 16,16,16
clear window
sphera()
sub sphera()
local n
for n = 1 to 100
color 2*n, 2*n, 2*n
fill circle ancho/2-2*n/3, alto/2-n/2, 150-n
next n
end sub