Originally Posted by Mrs Beanbag
But that is the case anyway, if you are saving the background behind each bob.
But again, a tiny bob may be in 4 different tiles. Potentially only 1 pixel high in the corner of 4 different tiles.
Then you're comparing one save/draw/restore operation (and the save/restore is only a single blit using interleaved bitplanes) vs a minimum of 4 blits to restore the backgrounds and you have to first work out how much is obscured from each tile to determine you're doing 4 blits of 1 pixel high. And the chances of a bob overlapping more than one tile is at least 15/16. The only case where it wouldn't is a bob 16 pixels wide that fits perfectly inside the tile, so aligned on the edges.