I will present the results of a recent optical and near infrared spectroscopic survey of the young Galactic supernova remnant Cassiopeia A (Cas A). The survey includes the remnant's bright main shell and streamers of high-velocity material. From these data an extensive, high-resolution, three-dimensional (3D) kinematic reconstruction has been created that provides us with the clearest look yet at the explosive outcome of a Type IIb supernova. I will discuss the observed complex ejecta structure in the context of potential explosion mechanisms, and offer a few thoughts on how these results can improve our understanding of core-collapse supernova dynamics in general.