A simple BRST system with quadratically constrained ghosts
  I present a toy model for the Berkovits pure spinor superparticle. It is a D=1, N=2 superparticle with no physical degrees of freedom. We study the cohomology in various ways, in particular finding an explicit expression for the `b'-field. Finally, we construct the topological string B-model from a straightforward generalization of the system. 
Michael Chesterman