It is believed this storage is done so that drawing a sprite facing left, and drawing a sprite facing right will take the same cpu time and this means a more stable frame rate regardless of the direction each sprite is facing.
* There is a list of sprites per level. The start address of this is stored at &e00 from the start of the level data. This takes the form of width, height and pixel data location. With 128KB there is 1 extra ram page per level for level specific sprites. Sprites common to each level are stored in main RAM. There are around 223 sprites (including common sprites). During the game the level page is mapped into RAM at &4000.
=== Levels ===