BTW, Stockholm's subway used to up until very recently have dot-matrix LED signs with what I think did a neat embedded-programming trick. They could switch between a static message and scrolling text, but the scrolling text was slanted.

I think the slanting was done by varying the timing for each row of LEDs. The bottom row was scrolled first, then the next above it after a short delay, and so on.

I have been thinking of trying that trick for making scrolling text legible on a keyboard with backlit keys in a traditional row-staggered configuration. But I would first need a keyboard PCB for DIY with individually addressable LEDs.