Pipe
    fluid_box = Fluid Box
    pictures = Pipe Pictures
    
Pipe Pictures - not an official class/type but logically grouped (all Sprites unless otherwise stated)
    straight_vertical_single
    straight_vertical
    straight_vertical_window
    straight_horizontal
    straight_horizontal_window
    corner_up_right
    corner_up_left
    corner_down_right
    corner_down_left
    t_up
    t_down
    t_right
    t_left
    cross
    ending_up
    ending_down
    ending_right
    ending_left
    horizontal_window_background
    vertical_window_background
    fluid_background
    low_temperature_flow
    middle_temperature_flow
    high_temperature_flow
    horizontal_window_bounding_box = BoundingBox
    vertical_window_bounding_box = BoundingBox
