@neauoire I originally tried laying out all the tiles contiguously in the specified order (2x tiles tall for UF2), and then selecting slices from that offsetting by character widths, which was as wrong as it was overcomplicated.

The way it acutally works obviously makes way more sense -- pixel data is always the same size and the character widths are just bounds inside it.

This is obvious in retrospect but somehow wasn't to me at the beginning! 😅