New day, new Problem: I’d like to fade out the current content of a matrix based on a vektor/angle. With nscale() tricks i’ve managed to move the tail in 0, 45, 90, 135, … degree steps. But I need it in any direction in order to rotate in realtime for a spiral fade out. Has somebody done that already? Or just an abstract idea, how to do it? I thought, maybe the Bresenham’s line algorithm could help, but there I’ve no idea, how to manage the color decay along the line. Or maybe reading a circle and then fade it down and scale it into a circle with 2 pixel more in diameter. With other words: I’m a bit lost and frustrated, that my imagination is far ahead my programming skills… 
All I can imagine right now is to save the current frame in a second array, rotate it a bit, zoom in a bit and then write it semitransparent over the imagebuffer itself. Oh god, it’s so many years ago, that i worked the last time with image manipulation… But I still like the idea, of doing it all in ONE framebuffer.
(It reminds me of my trys to scroll a screencontent at times where personal computers where slower than a Teensy today. No chance to copy that amout of data fast enough. The solution was so have a videobuffer bigger than the screen itself and than leave it’s content untouched and just manipulate the starting adress - synchronized with the retrace signal from the monitor it looked really cool on a 80286…)
Just, that I’m serious… What happened today on my setup and you see here is based on a flow in only one fixed direction - downwards 
http://www.youtube.com/watch?v=yo3j3U2NINg&feature=youtu.be
Imagine, how cool it might look with a twisting tail…
(What is it? The left half of 3 independent dots following different Lissajous figures with changing colors, a little tail behind every single one, a bigger tail down. Only 9 variables changing. Time until you see something twice on the screen…out of range…)
Oh, you have a proper name now?
Yes… and a face.