What is Hückel method?

The Hückel method computes the $\pi$ orbitals of a planar conjugated system as combinations $\psi = \sum_r c_r p_r$ of one p orbital per atom, with the approximations: overlaps $S_{rs} = 0$ for $r \neq s$ (and 1 for $r = s$); Coulomb integrals all equal to $\alpha$; resonance integrals equal to $\beta < 0$ between bonded neighbours and zero otherwise.