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Why 7x7 tiles? Is 8x8 not a much more natural size?


Not in that graphics mode on an Apple II. 7 bits of each byte gives you pixels, the eighth determines which bichromatic palette to use for those 7 pixels.

https://en.wikipedia.org/wiki/Apple_II_graphics#High-Resolut...

> The Apple II's Hi-Res mode was peculiar even by the standards of the day. [...] Each row of 280 pixels was broken up into 40 blocks of seven pixels each, represented in a single byte. Each pair of adjacent pixels generated a single color pixel via artifact color, resulting in an effective resolution of 140×192. The lower seven bits of each byte represented the pixels, while the most significant bit controlled the phase offset for that block of pixels, altering the color that was displayed.




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