  In this paper, we present an exactly solvable model for two dimensional
topological superconductor with helical Majorana edge modes protected by time
reversal symmetry. Our construction is based on the idea of decorated domain
walls and makes use of the Kasteleyn orientation on a two dimensional lattice,
which was used for the construction of the symmetry protected fermion phase
with $Z_2$ symmetry in Ref. \onlinecite{Tarantino2016,Ware2016}. By decorating
the time reversal domain walls with spinful Majorana chains, we are able to
construct a commuting projector Hamiltonian with zero correlation length ground
state wave function that realizes a strongly interacting version of the two
dimensional topological superconductor. From our construction, it can be seen
that the $T^2=-1$ transformation rule for the fermions is crucial for the
existence of such a nontrivial phase; with $T^2=1$, our construction does not
work.
