{
    (b) ////[b][b_double][b_double][b_double][b_double]
|
    x16
}

{
    {       (higher) (zq)(lb)(hb)    /  [higher]             /[lb][b!] | 2x2b }
    {       (higher) (zq)(lb)(hb)    ///[higher][2x2b][hb   ]/[lb][b!] | 4x2b }
    {       (higher) (zq)(lb)(hb)    ///[higher][4x2b][hb   ]/[lb][b!] | 8x2b }
    {       (higher) (zq)(lb)(hb)    ///[higher][8x2b][hb   ]/[lb][b!] | xx2b }
    (lower) (higher)      ////[b0][xx2b][higher][xx2b][lower]
|
    xx2b
}