NAME
bridges - topological deduction game
SYNOPSIS
bridges [--generate n] [--print wxh [--with-solutions] [--scale n]
[--colour]] [game-parameters|game-ID|random-seed]
bridges --version
DESCRIPTION
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:
â.
Bridges run horizontally or vertically.
â.
The number of bridges terminating at any island is equal to the
number written in that island.
â.
Two bridges may run in parallel between the same two islands,
but no more than two may do so.
â.
No bridge crosses another bridge.
â.
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 Nikoli
(http://www.nikoli.co.jp/puzzles/14/index-e.htm).
Bridges was contributed to this collection by James Harvey.
Bridges controls
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 do not have
a bridge between them, you can right-drag between them in the same way
to draw a â.PP 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.
You can also use the cursor keys to move around the grid: if possible
the cursor will always move orthogonally, otherwise it will move
towards the nearest island to the indicated direction. Pressing the
return key followed by a cursor key will lay a bridge in that direction
(if available); pressing the space bar followed by a cursor key will
lay a â.PP You can mark an island as finished by pressing the return
key twice.
Violations of the puzzle rules will be marked in red:
â.
An island with too many bridges will be highlighted in red.
â.
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.
â.
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.
â.
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 below are also available.)
Bridges parameters
These parameters are available from the â.IP "Width, Height" Size of
grid in squares.
Difficulty
Difficulty level of puzzle.
Allow loops
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.
Max. bridges per direction
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.
%age of island squares
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.
Expansion factor (%age)
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.
Common actions
These actions are all available from the â.PP (On Mac OS X, to conform
with local user interface standards, these actions are situated on the
â.IP "New game (âStarts a new game, with a random initial state.
Restart game
Resets the current game to its initial state. (This can be
undone.)
Load Loads a saved game from a file on disk.
Save Saves the current state of your game to a file on disk.
The Load and Save operations preserve your entire game history
(so you can save, reload, and still Undo and Redo things you had
done before saving).
Print Where supported (currently only on Windows), brings up a dialog
allowing you to print an arbitrary number of puzzles randomly
generated from the current parameters, optionally including the
current puzzle. (Only for puzzles which make sense to print, of
it’s hard to think of a sensible printable representation of Fifteen!)
course â.IP "Undo (âUndoes a single move. (You can undo moves
back to the start of the session.)
Râ, Ctrl+âRâ) Redo
(â.
Redoes a previously undone move.
Copy Copies the current state of your game to the clipboard in text
format, so that you can paste it into (say) an e-mail client or
a web message board if you’re discussing the game with someone
else. (Not all games support this feature.)
Solve Transforms the puzzle instantly into its solved state. For some
games (Cube) this feature is not supported at all because it is
of no particular use. For other games (such as Pattern), the
solved state can be used to give you information, if you can’t
see how a solution can exist at all or you want to know where
you made a mistake. For still other games (such as Sixteen),
automatic solution tells you nothing about how to get to the
solution, but it does provide a useful way to get there quickly
so that you can experiment with set-piece moves and
transformations.
Some games (such as Solo) are capable of solving a game ID you
have typed in from elsewhere. Other games (such as Rectangles)
cannot solve a game ID they didn’t invent themself, but when
they did invent the game ID they know what the solution is
already. Still other games (Pattern) can solve some external
game IDs, but only if they aren’t too difficult.
The â.RE
Qâ,
Ctrl+âQâ)
Quit (â.
Closes the application entirely.
Specifying games with the game ID
There are two ways to save a game specification out of a puzzle and
recreate it later, or recreate it in somebody else’s copy of the same
puzzle.
The â.PP You can enter either of these pieces of text back into the
program (via the same â.PP The difference between the two forms is that
a descriptive game ID is a literal description of the initial state of
the game, whereas a random seed is just a piece of arbitrary text which
was provided as input to the random number generator used to create the
puzzle. This means that:
â.
Descriptive game IDs tend to be longer in many puzzles (although
some, such as Cube (cube(6)), only need very short
descriptions). So a random seed is often a quicker way to note
down the puzzle you’re currently playing, or to tell it to
somebody else so they can play the same one as you.
â.
Any text at all is a valid random seed. The automatically
generated ones are fifteen-digit numbers, but anything will do;
you can type in your full name, or a word you just made up, and
a valid puzzle will be generated from it. This provides a way
for two or more people to race to complete the same puzzle: you
think of a random seed, then everybody types it in at the same
time, and nobody has an advantage due to having seen the
generated puzzle before anybody else.
â.
It is often possible to convert puzzles from other sources (such
"
as â.IP "âRandom seeds are not guaranteed to produce the same
result if you use them with a different version of the puzzle
program. This is because the generation algorithm might have
been improved or modified in later versions of the code, and
will therefore produce a different result when given the same
sequence of random numbers. Use a descriptive game ID if you
aren’t sure that it will be used on the same version of the
program as yours.
(Use the â.RE
A descriptive game ID starts with a piece of text which encodes
the parameters of the current game (such as grid size). Then
there is a colon, and after that is the description of the
game’s initial state. A random seed starts with a similar string
of parameters, but then it contains a hash sign followed by
arbitrary data.
If you enter a descriptive game ID, the program will not be able
to show you the random seed which generated it, since it wasn’t
generated from a random seed. If you enter a random seed,
however, the program will be able to show you the descriptive
game ID derived from that random seed.
Note that the game parameter strings are not always identical
between the two forms. For some games, there will be parameter
data provided with the random seed which is not included in the
descriptive game ID. This is because that parameter information
is only relevant when generating puzzle grids, and is not
important when playing them. Thus, for example, the difficulty
level in Solo (solo(6)) is not mentioned in the descriptive game
ID.
These additional parameters are also not set permanently if you
type in a game ID. For example, suppose you have Solo set to
â.SH "The â.PP The â.PP The â.SH "Specifying game parameters on
the command line"
(This section does not apply to the Mac OS X version.)
The games in this collection deliberately do not ever save
information on to the computer they run on: they have no high
score tables and no saved preferences. (This is because I expect
at least some people to play them at work, and those people will
probably appreciate leaving as little evidence as possible!)
However, if you do want to arrange for one of these games to
default to a particular set of parameters, you can specify them
on the command line.
The easiest way to do this is to set up the parameters you want
using the â.PP If you run the game with just that parameter text
on the command line, it will start up with the settings you
specified.
Octahedronâ from the âTypeâ menu, and then go to the game ID selection, you will see a string of the form âo2x2#338686542711620â. Take only the part before the hash (âo2x2â), and start Cube with that text on the command line: âcube o2x2â.
For example: if you run Cube (see cube(6)), select â.PP If you
copy the entire game ID on to the command line, the game will
start up in the specific game that was described. This is
occasionally a more convenient way to start a particular game ID
than by pasting it into the game ID selection box.
(You could also retrieve the encoded game parameters using the
â.SH "Unix command-line options"
(This section only applies to the Unix port.)
In addition to being able to specify game parameters on the
command line (see above), there are various other options:
--game
--load These options respectively determine whether the command-
line argument is treated as specifying game parameters or
a save file to load. Only one should be specified. If
neither of these options is specified, a guess is made
based on the format of the argument.
--generate n
If this option is specified, instead of a puzzle being
displayed, a number of descriptive game IDs will be
invented and printed on standard output. This is useful
for gaining access to the game generation algorithms
without necessarily using the frontend.
If game parameters are specified on the command-line,
they will be used to generate the game IDs; otherwise a
default set of parameters will be used.
The most common use of this option is in conjunction with
--print, in which case its behaviour is slightly
different; see below.
--print wxh
If this option is specified, instead of a puzzle being
displayed, a printed representation of one or more
unsolved puzzles is sent to standard output, in
PostScript format.
On each page of puzzles, there will be w across and h
down. If there are more puzzles than wÃh, more than one
page will be printed.
If --generate has also been specified, the invented game
IDs will be used to generate the printed output.
Otherwise, a list of game IDs is expected on standard
input (which can be descriptive or random seeds; see
above), in the same format produced by --generate.
For example:
net --generate 12 --print 2x3 7x7w | lpr
will generate two pages of printed Net puzzles (each of
which will have a 7Ã7 wrapping grid), and pipe the output
to the lpr command, which on many systems will send them
to an actual printer.
There are various other options which affect printing;
see below.
--save file-prefix [ --save-suffix file-suffix ]
If this option is specified, instead of a puzzle being
displayed, saved-game files for one or more unsolved
puzzles are written to files constructed from the
supplied prefix and/or suffix.
If --generate has also been specified, the invented game
IDs will be used to generate the printed output.
Otherwise, a list of game IDs is expected on standard
input (which can be descriptive or random seeds; see
above), in the same format produced by --generate.
For example:
net --generate 12 --save game --save-suffix .sav
will generate twelve Net saved-game files with the names
game0.sav to game11.sav.
--version
Prints version information about the game, and then
quits.
The following options are only meaningful if --print is also
specified:
--with-solutions
The set of pages filled with unsolved puzzles will be
followed by the solutions to those puzzles.
--scale n
Adjusts how big each puzzle is when printed. Larger
numbers make puzzles bigger; the default is 1.0.
--colour
Puzzles will be printed in colour, rather than in black
and white (if supported by the puzzle).
SEE ALSO
Full documentation in /usr/share/doc/sgt‐puzzles/puzzles.txt.gz.