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