I remember working with the Amstrad PCW, which had an interesting layout for the video memory. The pixels in the 90x32 character monochrome display were stored in character order. The 1st 8 bytes were the leftmost character, the next 8 were the character to the right, and so on. This wasn't the only complexity as there was a lookup table to give the memory location of each of the 32 screen lines. The advantage of this table was very quick character scrolling, at the expense of computing the location of individual pixels. It was rather tricky to write quick Z80 code to draw line with this quirky setup, but some people managed some rather nice vector games, such as Starglider.