Fluid Box
    base_area = d(1)
    base_level = d(0)
    height = d(1)
    pipe_covers = Sprite4Way
    pipe_picture = Sprite4Way
    pipe_connections = pipe_connection list

    production_type = "None" or "input" or "output" (default = "None")
    
errors:
    if not production_type.valid
        throws error(string.format("Unknown value %s for fluidbox production type.", production_type)
