From a bug report. The first report complained about levitation
allowing you to move through water on the Plane of Water, something that's
come up in the newsgroup lots of times (mostly about how levitation is
the best way to get around, only occasionally wondering why it works:
water walking doesn't work there because there's no surface, so where are
you levitating such that you're kept dry?) The second report complained
about being told you were floating up if you put on a ring of levitation
while stuck inside a wall (perhaps after being stranded when polymorph
into xorn form ended).
This implements intrinsic blocking for levitation and also for
flying. Being inside solid rock (or closed door) anywhere and being in
water on the Plane of Water are the things that do it for levitation;
those two and levitating are what do it for flying. Entering such
terrain turns off ability to float/fly, and leaving there turns it back
on; starting levitation blocks flight, ending it unblocks (levitation
has always overridden flying's ability to reach the floor). Being able
to phase through rock doesn't prevent levitation and flight from being
blocked while in rock; you aren't floating or flying in that situation.
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