We describe a method for treating fluctuations in two-dimensional superconducting films in zero magnetic field. The method involves expanding the order parameter [psi]([ital x],[ital y]) in empty-lattice Wannier functions of a fictitious square lattice. Despite the discrete basis, the order parameter is [ital continuous] and has no unphysical pinning. The thermodynamics of the model is a function of a single variable analogous to the Josephson coupling in granular superconductors. We estimate the Kosterlitz-Thouless (KT) transition temperature [ital T][sub [ital c]] of the model by Monte Carlo techniques. If amplitude fluctuations are neglected, the model reduces to a partially frustrated [ital XY] Hamiltonian, even in zero magnetic field. With amplitude fluctuations, [ital T][sub [ital c]] is further reduced, the Coulomb-gas scaling hypothesis of Minnhagen is automatically satisfied, and the jump in superfluid density at the transition may possibly be nonuniversal. Snapshots of [psi]([ital x],[ital y]) near [ital T][sub [ital c]] reveal the rapid development of pairs of oppositely charged vortices, accompanied by zeros of the order parameter, and, above [ital T][sub [ital c]], by unpaired vortices, in agreement with the original KT picture. The extension of this approach to layered three-dimensional superconductors is briefly discussed.