Chapter 2: Common features

This chapter describes features that are common to all the games.

2.1 Common actions

These actions are all available from the Game menu and via keyboard shortcuts, in addition to any game-specific actions.

About the Solve Function

The Solve command works differently depending on the game:

• 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 themselves, 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.

Preferences

One option common to all games allows you to turn off the one-key shortcuts like N for new game or Q for quit, so that there’s less chance of hitting them by accident. You can still access the same shortcuts with the Ctrl key.

2.2 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).

Descriptive Game ID vs Random Seed

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, 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.

Game ID Format

• 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.

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.

2.3 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.

2.4 Specifying game parameters on the command line

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, and then to select Random Seed from the Game or File menu. 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.

Example

If you run Cube, 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:

PREFIX-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.

2.5 Unix command-line options

In addition to being able to specify game parameters on the command line, there are various other options:

Basic Options

Printing Options

Save Options

Examples

Generate and print Net puzzles:

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

This will generate two pages of printed Net puzzles (each with a 7×7 wrapping grid), and pipe the output to the lpr command.

Generate saved game files:

PREFIX-net --generate 12 --save game --save-suffix .sav

This will generate twelve Net saved-game files with the names game0.sav to game11.sav.