  The manipulation of topologically-ordered phases of matter to encode and
process quantum information forms the cornerstone of many approaches to
fault-tolerant quantum computing. Here we demonstrate that fault-tolerant
logical operations in these approaches can be interpreted as instances of anyon
condensation. We present a constructive theory for anyon condensation and, in
tandem, illustrate our theory explicitly using the color-code model. We show
that different condensation processes are associated with a general class of
domain walls, which can exist in both space- and time-like directions. This
class includes semi-transparent domain walls that condense certain subsets of
anyons. We use our theory to classify topological objects and design novel
fault-tolerant logic gates for the color code. As a final example, we also
argue that dynamical `Floquet codes' can be viewed as a series of condensation
operations. We propose a general construction for realising planar dynamically
driven codes based on condensation operations on the color code. We use our
construction to introduce a new Calderbank-Shor Steane-type Floquet code that
we call the Floquet color code.
