Making the (almost) perfect square wave. Can it be done?

Continue adding up sine waves until you get an almost perfect square wave.
Try changing the number of terms that make up the sum. Move the mouse over the sines/cosines to see each frequency's contribution to the sum.
Try also changing the playing frequency (with your computer's sound ON)
Go to this site: http://www.falstad.com/fourier/e-square.html