// complex data is passed and manipulated in structures
struct World {
    // each member is defined by name and type
    u32 xsize,
    u32 ysize,
    BitArray current,
    u32 numdots,
    BitArray next,

    // TODO: members can have default initialization values
    // i32 xmin = 1'000'000,
    // i32 xmax = -1,
    // i32 ymin = 1'000'000,
    // i32 ymax = -1,

    i32 xmin,
    i32 xmax,
    i32 ymin,
    i32 ymax,
}