In one issues of the The Sinc Times I do discover a program called Sprite Basic. The routines are very good and provides a lot of functions to help manage Sprites on the ZX81.
That is good, but what call my attention was the explanation of the INIT function which manage the sprites movement using an in interrupt handler.
Many times I do read about the Interrupt facilities of the Z80, but ever saw some uses on the Spectrum machines. I think until now that the ZX81 can not manage interrupt routines...
Some of you are really clever ZX81 users and programmers, so maybe you already know that, in that case sorry by the old news

I decide to type in the program in order to see it working... and guess what ? bad luck, because the listing are impossible to read...
I found on the zx81.nl site (inside and ARJ archive) the Basic Sprite Demo !!! but this version is not working. Fix it was easy and now I have a version that works.
I happy with this discovery and I like to share it with all of you, so I put a little video showing all this

http://www.youtube.com/watch?v=3Cvyxm8PR4s
Thanks,
Gus
P.D. Do you know of another programs having some Interrupt Routines ???