favorite RGB LED effects?

I glanced over the code. I assume it writes out lines... that means, that the text has to be vertical, is it?

Sort of.
Actually the picture buffer stores 50 lines (should have named that "spokes" or "columns" to make it clearer).
The g Graphics object takes care of the mapping. From g's side the picture is drawn horizontally.
The point is to have each "spoke" ready to be pushed out to the LEDs as an array in function refresh() just after choosing which spoke it actually is at that point in time/revolution.

Next thing is to see this powered by a dynamo...

Would be nice, but I don't think so. It's not trivial to get the power from the fixed dynamo/fork to the rotating wheel. The batteries would last for hours anyway - and besides that it isn't even legal on German roads, so why push it any further?
It was just an experiment - a proof of concept for me.

PS: just found another picture of an old-fashioned digital camera with some longer shutter time.
It doesn't show the nice rainbow colours as nicely, but you get a better impression of the whole frame.

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