$\vec{n}$

P: (0 | 0 | 4)
N = (4, 0, 12)
n = Vector(P, N)
u = If(x(n) ≟ 0, (1 | 0 | 0), If[y(n) ≟ 0, (0 | 1 | 0), If[z(n) ≟ 0, (0 | 0 | 1), ((-y(n)) | x(n) | 0)]])
v: n ⊗ u
v0: v / abs(v)
u0: u / abs(u)
Q1: P + (8 * u0) + (8 * v0)
Q3: P - (8 * u0) - (8 * v0)
Q4: P + (8 * u0) - (8 * v0)
Q2: P - (8 * u0) + (8 * v0)
v1, q2, q3, q4, q1 = Polygon(Q2, Q3, Q4, Q1)
a: (u0 * n)
b: (v0 * n)
c: (u0 * v0)
g1 = Line((1 | 1 | 4), (3 | 5 | 12))
g2 = Line((1 | -1 | 4), (3 | 3 | 12))
g3 = Line((-1 | 1 | 4), (1 | 5 | 12))