Flat surface types refer to two-dimensional surfaces such as tabletops. This is the most common form of surface computing in the commercial space as seen by products like Microsoft’sMicrosoft's PixelSense and iTable. The aforementioned commercial products utilize a multi-touch LCD screen as a display, but other implementations use projectors. Part of the appeal of two-dimensional surface computing is the ease and reliability of interaction. Since the advent of tablet computing, a set of intuitive gestural interactions have been developed to compliment two-dimensional surfaces. However, the two-dimensional plane limits the range of interactions a user is able to perform. Furthermore, interactions are only detected when making direct contact with the surface. In order to afford the user a wider range of interaction, research has been done to augment the interaction schemes for two-dimensional surfaces. This research involves using the space above the screen as another dimension for interaction, so, for example, the height of a user’suser's hands above the surface becomes a meaningful distinction for interaction. This particular system would qualify as a hybrid that uses a flat surface, but a three-dimensional space for interaction.<ref name=":0">{{Cite web|url = http://research.microsoft.com/pubs/132463/hilliges2009uist.pdf|title = Interaction in the Air: Adding Further Depth to Interactive Tabletops|date = |accessdate = |website = |publisher = |last = |first = }}</ref>
