The design of the behavior of non-player characters (NPCs) in a game is a collaborative task between programmers and designers. Nevertheless this collaboration is an open problem since the limits, responsibilities and competences are not well defined.Behavior trees are the technology of choice nowadays for programming the behavior of NPCs, and they are first and foremost a programmers tool. In this paper we describe an experiment that shows that with the right division of labor and a reduced background in Programming, designers can also build behavior trees and thus find a principled way to collaborate with programmers in that task.