Moving from flat screens into the physical world is an ongoing trend of HCI. Spatial augmented reality (SAR) augments the real world using projectors. It is used in multiple disciplines, especially in design and creative environments such as prototyping and artistic installations. Still, interaction with SAR is little explored. The objective of this thesis is to study SAR and its rich space for interaction, and find novel techniques to take advantage of it. First, previous work on SAR must be studied, then experimental prototypes have to be implemented and evaluated. This paper presents a brief introduction to technical aspects that need to be addressed, in addition to a study of the design spaces related to SAR. A first proof of concept is provided: using augmented objects in front of the screen, as part of a standard desktop environment work-flow. Future work will involve iteratively creating prototypes exploring the identified strengths and weaknesses of SAR, analyzing the viability of such prototypes via dedicated user studies.