Ubuntu Manpage: sgt-bridges - Bridge-placing puzzle

Provided by: sgt-puzzles_20191231.79a5378-3_amd64

NAME

       sgt-bridges - Bridge-placing puzzle

SYNOPSIS

       sgt-bridges [--generate n] [--print wxh [--with-solutions] [--scale n] [--colour]] [game-parameters|game-
       ID|random-seed]

       sgt-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:

       •      Bridges run horizontally or vertically.

       •      The number of bridges terminating at any island is equal to the number written in that island.

       •      Two bridges may run in parallel between the same two islands, but no more than two may do so.

       •      No bridge crosses another bridge.

       •      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/en/puzzles/hashiwokakero.html (beware of
       Flash)).

       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 ‘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.

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. Holding
Control and pressing a cursor key will lay a bridge in that direction (if available); Shift and a cursor
key will lay a ‘non-bridge’ marker. Pressing the return key followed by a cursor key will also lay a
bridge in that direction.

You can mark an island as finished by pressing the space bar or by pressing the return key twice.

By pressing a number key, you can jump to the nearest island with that number. Letters ‘a’, ..., ‘f’
count as 10, ..., 15 and ‘0’ as 16.

Violations of the puzzle rules will be marked in red:

• An island with too many bridges will be highlighted in red.

• 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.

• 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.

• 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 ‘Custom...’ option on the ‘Type’ menu.

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 ‘Game’ menu and via keyboard shortcuts, in addition to any game-
specific actions.

(On Mac OS X, to conform with local user interface standards, these actions are situated on the ‘File’
and ‘Edit’ menus instead.)

New game (‘N’, Ctrl+‘N’)
Starts 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 course – it's hard to think of a sensible
printable representation of Fifteen!)

Undo (‘U’, Ctrl+‘Z’, Ctrl+‘_’)
Undoes a single move. (You can undo moves back to the start of the session.)

Redo (‘R’, Ctrl+‘R’)
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 ‘Solve’ command adds the solved state to the end of the undo chain for the puzzle. In other
words, if you want to go back to solving it yourself after seeing the answer, you can just press
Undo.

Quit (‘Q’, Ctrl+‘Q’)
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 ‘Specific’ and ‘Random Seed’ options from the ‘Game’ menu (or the ‘File’ menu, on Mac OS X) each show
a piece of text (a ‘game ID’) which is sufficient to reconstruct precisely the same game at a later date.

You can enter either of these pieces of text back into the program (via the same ‘Specific’ or ‘Random
Seed’ menu options) at a later point, and it will recreate the same game. You can also use either one as
a command line argument (on Windows or Unix); see below for more detail.

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:

• Descriptive game IDs tend to be longer in many puzzles (although some, such as Cube (sgt-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.

• 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.

• It is often possible to convert puzzles from other sources (such as ‘nonograms’ or ‘sudoku’ from
newspapers) into descriptive game IDs suitable for use with these programs.

• Random 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 ‘About’ menu option to find out the version number of the program. Programs with the same
version number running on different platforms should still be random-seed compatible.)

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 (sgt-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 ‘Advanced’ difficulty level, and then a friend wants your help with a ‘Trivial’
puzzle; so the friend reads out a random seed specifying ‘Trivial’ difficulty, and you type it in. The
program will generate you the same ‘Trivial’ grid which your friend was having trouble with, but once you
have finished playing it, when you ask for a new game it will automatically go back to the ‘Advanced’
difficulty which it was previously set on.

The ‘Type’ menu

       The  ‘Type’  menu,  if  present,  may contain a list of preset game settings. Selecting one of these will
       start a new random game with the parameters specified.

       The ‘Type’ menu may also contain a ‘Custom’ option which allows you to  fine-tune  game  parameters.  The
       parameters available are specific to each game and are described in the following sections.

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 ‘Type’ menu (see above), and
then to select ‘Random Seed’ from the ‘Game’ or ‘File’ menu (see above). The text in the ‘Game ID’ box
will be composed of two parts, separated by a hash. The first of these parts represents the game
parameters (the size of the playing area, for example, and anything else you set using the ‘Type’ menu).

If you run the game with just that parameter text on the command line, it will start up with the settings
you specified.

For example: if you run Cube (see sgt-cube(6)), select ‘Octahedron’ from the ‘Type’ menu, and then go to
the game ID selection, you will see a string of the form ‘o2x2#338686542711620’. Take only the part
before the hash (‘o2x2’), and start Cube with that text on the command line: ‘sgt-cube o2x2’.

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 ‘Specific’ menu option instead of ‘Random
Seed’, but if you do then some options, such as the difficulty level in Solo, will be missing. See above
for more details on this.)

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 w×h,
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:

sgt-net --generate 12 --print 2x3 7x7w | lpr

will generate two pages of printed Net puzzles (each of which will have a 7×7 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.

For example:

sgt-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).