########## About Phase Shift ###########



   The phase shift video is a superposition of three videos.
In blue, a tall Soliton wave travelling by itself.
In yellow, a short Soliton wave travelling by itself.
In purple, the two waves travelling together, colliding and reamerging from collision.
By superimposing the three one can clearly see that the purple tall wave, in phase with
it's blue counterpart before collision, emerges displaced slightly ahead.  By contrast, the
purple short wave, in phase with it's yellow counterpart before collision, emerges displaced slightly behind.