This looks really nice, but I am having a little trouble getting it working.
I copied the above into a included empty wdl along with your motion blur script
above it. Then I enclosed the alpha frame evaluation in a starter loop and set
set_visual_field(20, 0, 0); and no effect or error?
However, if I set "set_motion_blur(18);" with the same wdl, the motion blur
seems to work fine. so I must be missing something in this snippit. I will have
to work on this a little more.

I wonder if there is a way to make the outside blurred edge constantly move
outwards as if zooming in while the central area remains unblurred?

Thanks for sharing these ultra cool effects, very generous of you!