On the other hand, bitmaps stored in planar form were supported by many hardware systems in the time frame of the article(the Amiga, for one, used a planar sche

On the other hand, bitmaps stored in planar form were supported by many hardware systems in the time frame of the article(the Amiga, for one, used a planar scheme). This did allow for bitdepths other than powers of 2 with the requirement of resolutions being multiples of a byte or word(so, 8 or 16). This is particularly useful when considering overall asset storage constraints - 8 colors(3bpp) is often plenty for small sprites.