In this paper, we consider gestures as part of the resources activated in the mathematics classroom: speech, inscriptions, artifacts, etc. As such, gestures are seen as one of the semiotic tools used by students and teacher in mathematics teaching-learning. To analyze them, we introduce a suitable model, the "semiotic bundle." It allows focusing on the relationships of gestures with the other semiotic resources within a "multimodal" approach. It also enables framing the mediating action of the teacher in the classroom: in this respect, we introduce the notion of "semiotic game" where gestures are one of the major ingredients.