medu-343.des  Last edited 2006-12-02 for NetHack 3.4.3
Crossing the sea of Medusa using boulders in NetHack 3.4
Written for 3.4.3 by Janis Papanagnou.


Crossing the sea of the Medusa levels is most obviously done using some means
of levitation (ring, spell, potion, or boots of levitation, or the barbarians
quest artifact, "The Heart of Ahriman"). You may also just dig down on any
square that is not adjacent to any water square or level teleport down and
approach Medusa from below (how to pass the sea on your way back is the one
problem to be solved later, e.g. by using the water walking boots from Vlads
tower; the other problem is that you may need levitation, water walking or a
music instrument to enter the Castle).  If you have some means of producing
ice, a wand, a spell, or a frost horn, you can build a fragile(!) bridge to
cross the water. The ability to jump from island to island is also helpful to
cross (part of) the sea. Last but not least you can polyself to become some
creature that can fly over or dive through the sea.


This spoiler describes the alternative way using a bridge of solid land built
from boulders that, compared to the bridge of ice, has the advantage to not
be a death trap in case of a fire attack. And (unlike e.g. potions or boots
of levitation that vanish or occupy an armor slot) it's a (quite) persistent
solution that you may use on your way up and down the dungeon at any time.

You are guaranteed two scrolls of earth on the lowest Sokoban level that you
may use to cross Medusa's sea. There are two Medusa levels; the round island
level and the titan level. For the former level one scroll of earth may be
sufficient, for the latter you need two scrolls of earth. But be aware that
boulders may "sink without trace" with a probability of 10%; so make sure
that not a single boulder will be wasted. The titan level has two additional
boulders that can both be used for your purpose, one in the starting room and
the other on the distant island that you will pass on your way to Medusa.
Occasionally there may be giants generated to throw boulders, needless to say
that you should try to get hold of them in an area where you can push them to
your advance.


The specific solutions that are presented below take into account that you
occasionally need a square to maneuver the boulders in case of any direction
changes, and are minimal in this respect. If you have e.g. a wand of cold
you may use that to bridge such a maneuver space with ice and may choose an
slightly different path that requires fewer boulders (you can usually save one
or two boulders that way), without sacrificing the solid path approach of the
final path.

In the maps below you'll find the following characters used...

  X  - path built solely by boulders without additional means
  Y  - alternative paths that require squares of ice to maneuver boulders or
       slightly more than the minimum amount of boulders
  O  - additional boulders guaranteed to be existing on the level
  ?  - a safe square where you can read the scrolls of earth without disabling
       any boulder (by being too close at a wall or at water, etc.)

(To view the map I suggest to use Pasi's syntax highlighting available for
the editors vim and emacs; the paths and locations will be highlighted nicely
that way and much better visible.)


1. Round Island level

This Medusa level requires a minimum of eight boulders from one scroll of
earth.

MAP
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ENDMAP


2. Titan level

This Medusa level requires both of the guaranteed scrolls of earth from
Sokoban, but there are enough boulders available to compensate up to 3
traceless sinking boulders. Though the necessary number of boulders can
also in this case be further reduced by using a spare charge from a wand
of cold and choosing a slightly different path over the sea. This level
has some specifics to mention; the secret door top-left on the map has to
be kicked down to have the necessary room to push the boulders away from
the blocking wall. Take also care that you don't push any boulder to the
right wall, because of the water squares in the lower part of the room you
would waste a boulder. Finally many of the walls of the ruins in the middle
of the map will have to be broke down using some mandatory means of digging
to be able to build that path.

MAP
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ENDMAP


Note: The above briefly mentioned method to dig or level-teleport down
instead of crossing the sea will make it impossible to apply the boulder
method presented here; the Medusa levels are designed to require more
boulders if you start your way from the east side of the map!


And don't forget the blindfold!


Corrections and comments are welcome (janis_papanagnou@hotmail.com)