  We present the first experimental realization of a two-dimensional quantum
gas in a purely magnetic trap dressed by a radio frequency field in the
presence of gravity. The resulting potential is extremely smooth and very close
to harmonic in the two-dimensional plane of confinement. We fully characterize
the trap and demonstrate the confinement of a quantum gas to two dimensions.
The trap geometry can be modified to a large extent, in particular in a
dynamical way. Taking advantage of this possibility, we study the monopole and
the quadrupole modes of a two-dimensional Bose gas.
