  We present a pedagogical introduction to the problem of evolving a head on
collision of two Aichelburg-Sexl gravitational shock waves in D-dimensions,
using perturbative techniques. We follow a constructive approach with examples,
going in some detail through: the set up of the exact initial conditions and
their properties; perturbative methods in flat space-time with Green function
solutions; and numerical strategies to evaluate the integral solutions. We also
discuss, briefly, radiation extraction methods adapted to this problem,
together with some of the results for this system.
