Struct Shield 

pub struct Shield {
    pub mothers: [Figure; 4],
    pub daughters: [Figure; 4],
    pub nieces: [Figure; 4],
    pub witnesses: [Figure; 2],
    pub judge: Figure,
}

地占 shield chart：由 4 母图推出全部派生图。

Fields

mothers: [Figure; 4]

4 母图（随机起，每图 4 位）。

daughters: [Figure; 4]

4 女图 = 母块转置。

nieces: [Figure; 4]

4 侄图 = 母/女成对 XOR。

witnesses: [Figure; 2]

2 见证 [右, 左] = 侄成对 XOR。

judge: Figure

法官 = 两见证 XOR；恒为偶图（GF(2) 奇偶校验定理）。

Trait Implementations

impl Clone for Shield

fn clone(&self) -> Shield

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Copy for Shield

impl Debug for Shield

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.