Mirror it along another!
how?
find u_parallel and u_perp
on the left is ccw
on the right is cw
kinda logical aint it.
gets you a 2D Rotor grade 0 scalar + grade 2 bivector
uv = uₓvₓ(e₁e₁) + uₓvᵧ(e₁e₂) + uᵧvₓ(e₂e₁) + uᵧvᵧ(e₂e₂)
1 e₂e₁ -e₂e₁ 1