  We present a unifying picture of the compact, dense and dilute phases of
two-dimensional polymers. The lattice dependence of the scaling exponents for
compact polymers is reconciled with their universality in the dense and dilute
case. In particular, we show that violations of the fully-packing constraint in
the compact phase can be interpreted as magnetic screening in the associated
Coulomb gas, which induces a flow to either the dense or the dilute phase. When
more than one flavour of polymers is present the flow away from the compact
phase leads to a decoupling of the flavours, and the central charge decreases
by an integer. If charge asymmetry develops the polymer flavours may
independently flow to either of the two non-compact phases.
