To explore how people conceptualize a complex system, 232 university students were asked to sketch how a search engine works. While the sketches reveal a diverse range of visual and conceptual approaches, a subset of the sketches exhibit an underlying regularity for describing algorithmic processes. To explain this regularity, I propose the conceptual metaphor: A SEARCH ENGINE IS A SERIES OF TEXT TRANSFORMATIONS and describe a set of mappings from sketchable graphic markings to abstractions in the search engine domain. I believe that this metaphor can be applied to enable people to more effectively conceptualize, describe, and explore complex systems.