New puzzle from James H: `Bridges', another Nikoli job.

[originally from svn r6409]

1 files changed, 129 insertions, 0 deletions

diff --git a/puzzles.but b/puzzles.but
index 5a31676..878a186 100644
--- a/puzzles.but
+++ b/puzzles.but
@@ -1859,6 +1859,135 @@ puzzles require more complex deductions, but at present none of the
 available difficulty levels requires guesswork or backtracking.
 
 
+\C{bridges} \i{Bridges}
+
+\cfg{winhelp-topic}{games.bridges}
+
+You have a set of islands distributed across the playing area. Each
+island contains a number. Your aim is to connect the islands
+together with bridges, in such a way that:
+
+\b Bridges run horizontally or vertically.
+
+\b The number of bridges terminating at any island is equal to the
+number written in that island.
+
+\b Two bridges may run in parallel between the same two islands, but
+no more than two may do so.
+
+\b No bridge crosses another bridge.
+
+\b All the islands are connected together.
+
+There are some configurable alternative modes, which involve
+changing the parallel-bridge limit to something other than 2, and
+introducing the additional constraint that no sequence of bridges
+may form a loop from one island back to the same island. The rules
+stated above are the default ones.
+
+Credit for this puzzle goes to \i{Nikoli} \k{nikoli-bridges}.
+
+Bridges was contributed to this collection by James Harvey.
+
+\B{nikoli-bridges}
+\W{http://www.nikoli.co.jp/puzzles/14/index-e.htm}\cw{http://www.nikoli.co.jp/puzzles/14/index-e.htm}
+
+\H{bridges-controls} \i{Bridges controls}
+
+\IM{Bridges controls} controls, for Bridges
+
+To place a bridge between two islands, click the mouse down on one
+island and drag it towards the other. You do not need to drag all
+the way to the other island; you only need to move the mouse far
+enough for the intended bridge direction to be unambiguous. (So you
+can keep the mouse near the starting island and conveniently throw
+bridges out from it in many directions.)
+
+Doing this again when a bridge is already present will add another
+parallel bridge. If there are already as many bridges between the
+two islands as permitted by the current game rules (i.e. two by
+default), the same dragging action will remove all of them.
+
+If you want to remind yourself that two islands definitely \e{do
+not} have a bridge between them, you can right-drag between them in
+the same way to draw a \q{non-bridge} marker.
+
+If you think you have finished with an island (i.e. you have placed
+all its bridges and are confident that they are in the right
+places), you can mark the island as finished by left-clicking on it.
+This will highlight it and all the bridges connected to it, and you
+will be prevented from accidentally modifying any of those bridges
+in future. Left-clicking again on a highlighted island will unmark
+it and restore your ability to modify it.
+
+Violations of the puzzle rules will be marked in red:
+
+\b An island with too many bridges will be highlighted in red.
+
+\b An island with too few bridges will be highlighted in red if it
+is definitely an error (as opposed to merely not being finished
+yet): if adding enough bridges would involve having to cross another
+bridge or remove a non-bridge marker, or if the island has been
+highlighted as complete.
+
+\b A group of islands and bridges may be highlighted in red if it is
+a closed subset of the puzzle with no way to connect it to the rest
+of the islands. For example, if you directly connect two 1s together
+with a bridge and they are not the only two islands on the grid,
+they will light up red to indicate that such a group cannot be
+contained in any valid solution.
+
+\b If you have selected the (non-default) option to disallow loops
+in the solution, a group of bridges which forms a loop will be
+highlighted.
+
+(All the actions described in \k{common-actions} are also available.)
+
+\H{bridges-parameters} \I{parameters, for Bridges}Bridges parameters
+
+These parameters are available from the \q{Custom...} option on the
+\q{Type} menu.
+
+\dt \e{Width}, \e{Height}
+
+\dd Size of grid in squares.
+
+\dt \e{Difficulty}
+
+\dd Difficulty level of puzzle.
+
+\dt \e{Allow loops}
+
+\dd This is set by default. If cleared, puzzles will be generated in
+such a way that they are always soluble without creating a loop, and
+solutions which do involve a loop will be disallowed.
+
+\dt \e{Max. bridges per direction}
+
+\dd Maximum number of bridges in any particular direction. The
+default is 2, but you can change it to 1, 3 or 4. In general, fewer
+is easier.
+
+\dt \e{%age of island squares}
+
+\dd Gives a rough percentage of islands the generator will try and
+lay before finishing the puzzle. Certain layouts will not manage to
+lay enough islands; this is an upper bound.
+
+\dt \e{Expansion factor (%age)}
+
+\dd The grid generator works by picking an existing island at random
+(after first creating an initial island somewhere). It then decides
+on a direction (at random), and then works out how far it could
+extend before creating another island. This parameter determines how
+likely it is to extend as far as it can, rather than choosing
+somewhere closer.
+
+High expansion factors usually mean easier puzzles with fewer
+possible islands; low expansion factors can create lots of
+tightly-packed islands.
+
+
 \A{licence} \I{MIT licence}\ii{Licence}
 
 This software is \i{copyright} 2004-2005 Simon Tatham.