Thanks, I didn’t know about this bug technique. I might use it in the future, but for this design it provides no benefits, because the restriction to basic forms is mandated by the example it is build upon.

Yes, I probably should revisit the digits. Aphoria’s ‘6’ and ‘9’ are interesting, I only tried the triangles with square, not with the quarter-circles. I have tried that ‘3’ and a ‘B’-like shape before, but didn’t quite like it. I probably won’t change ‘1’, ‘4’ and ‘7’, because they’re quite distinctive now (for an European eye). I’ll think about ‘2’ and ‘5’. ‘0’ is currently the same as ‘O’ by the way, although I tried to make letters and numbers distinct.

Update: There are now alternate digits at ‘¹’ (1 or 7), ‘²’ (2), ‘³’ (3), ‘¼’ (4), ‘½’ = 0.5 (5), ‘¾’ (6), ‘¶’ (9).I’m still not satisfied with them, though.
I’ve also added more punctuation marks, but it’s a display typeface after all, so nothing incredibly usable.

I doubt it was a valid infringement claim since the logo needs to be red, uses rectangles (not squares), has a frame, includes just one letter (or graphic element that resembles a letter) and in many jurisdictions letters (and fonts) cannot be subject to copyright.