Tight Orientable Surfaces:  The orientable surfaces are the
sphere, and tori with any number of handles. Since a torus is a
sphere with a handle, every orientable surface can be described
as a sphere with some number of handles.  It is easy to find a
tight sphere: the standard round sphere will do (in fact, any
convex surface is a tight sphere; tightness is a generalization
of convexity). A polyhedral example is the cube.  Given a tight
surface, it is always possible to add a handle to the surface
without losing tightness. Kuiper gave the following two-handled
torus as an example of how to do this:  For the polyhedral case,
we can describe this process in more detail. Take any two faces
that are not co-planar, remove a triangle from the center of
each (below, left), then add a triangular tube between these two
holes (right).  The resulting surface is still immersed (since
the stars of the new vertices are embedded [More]) and tight
(since the new vertices are not extreme vertices and the new
handle does not c