General relativity is too hard. You can only solve the Einstein field equations with pen and paper for the most boring scenarios; anything more exciting than a lone black hole needs to be solved numerically. This is what the field of numerical relativity is all about, and I'll be giving a quick little intro to this area of study through the lens of gravitational wave astronomy, in which we need to know how spacetime behaves in the complex, dynamical scenario of two merging black holes. I'll introduce some basic concepts and common approaches to doing this, then talk a little bit about my own work trying to simulate black hole binaries that have a huge difference in component masses - something that is currently impossible in practical terms but will be needed for the upcoming LISA detector.