pub const sprites.width = 17
pub const sprites.height = 17 ; unused as sprite are all square
pub const sprites.size = 289 ; height x width

pub const sprites.rotation_0 = 0
pub const sprites.rotation_90 = 1
pub const sprites.rotation_180 = 2
pub const sprites.rotation_270 = 3

pub const sprites.empty = 0
pub const sprites.unimplemented = 1
pub const sprites.wall_end = 2
pub const sprites.wall_straight = 3
pub const sprites.wall_corner = 4
pub const sprites.robot = 5
pub const sprites.ghost = 6
pub const sprites.coin = 7
pub const sprites.max = 7 ; for lookup table