Remember that we had developed a model for the return map of the fore-aft degree of freedom of this spring loaded inverted pendulum. And we had posited given a closed loop and return map, the imposition of a feedback law. And we would thereby close the loop, leading to a closed loop discreet dynamical system governed by the SLIP return map. The question now is what's the consequence of that feedback law? What sorts of feedback laws will have what sorts of fixed points, equilibrium states?