The bifurcations of strange nonchaotic attractors in quasi-periodically
forced systems are poorly understood. A simple two-parameter example
is introduced which unifies previous observations of
non-smooth pitchfork bifurcations and blowout bifurcations of strange
nonchaotic attractors. The corresponding bifurcation curves can
be calculated analytically. The example shows how these bifurcations
are organized around a codimension two point in parameter space.