In this paper we demonstrate how a design-based methodology can be used to iteratively produce designs for an information-processing architecture that integrates various intelligent capabilities. This methodology allows us to explain system performance in terms of changes to an existing architecture design, with the explanations being supported by performance data from an implementation of the design. We present an instance of this design methodology applied to the development of an architecture that integrates anytime deliberative capabilities with reactive behaviours and goal management. Iterations of the design are implemented and evaluated in the computer game Unreal Tournament.