Petr van Blokland Bitcount originally started as an (5×7) experiment in 1979 to see what the smallest bitmap size of a typeface is, that still can hold a readable lowercase with true ascenders and descenders. Counterintuitively, keeping thick and thin “strokes”, even at this low resolution, shows that contrast solves many of the problems that otherwise exist in pixel fonts. Altering pixel shapes, this became a 4-axis Variable Font, released at Type Network and Adobe Fonts.
Recently the family was updated as TYPETR Bitcount Ink at Google Fonts, implementing COLRv1 functionality. Adding 6 more axes for 2 color layers gives an almost infinite amount of pixel shapes. A special technique (splitting color and mask) was applied to avoid the creation of an unworkable 10-dimensional workspace. Bitcount Ink is both a demo of what the COLRv1 standard is capable of doing but also makes a great tool for typographic animations.