# Creating an Undum Game

## File Structure

An Undum game consists of a single HTML file. This imports the game engine and any supporting files. It also provides the structure needed for Undum to place content correctly on-screen.

The Undum engine consists of a single Javascript file, undum.js. In order to work, however, it needs supporting files. It requires the jQuery library (http://jquery.com) to be already imported, and it requires a game definition file to be imported after it.

The normal pattern of imports in the HTML file is therefore:

<script type="text/javascript" src="media/js/jquery-1.4.2.min.js"></script>
<script type="text/javascript" src="media/js/undum.js"></script>
<script type="text/javascript" src="media/js/mygame.game.js"></script>


By convention, the Javascript files are held in a media/js directory, but this is not enforced, you can arrange these files as you like, as long as you update the references to match.

In addition to the Javascript files, Undum expects the HTML file that imports it to have a particular structure. Although there is a good deal of flexibility, if you need it, you should start with the HTML file that is provided.

Finally, the HTML file will include a CSS file that controls the look and feel of the page. There are some elements in the CSS file which are used by Undum, and so, as for the HTML page, you should start with the CSS files provided. In most cases you will be able to leave the CSS file untouched, or else just tweak colors and image imports to match your game's style.

## The HTML File

The sample HTML file provided shows the key points to edit. They are:

• The game's title.

• The top-left panel title and summary (you can leave this as an explanation of Undum, or change it to be more game-specific).

• The copyright message. Please note that there are two copyright lines, the second one is the acknowledgment that your game is based on Undum. You must leave the second line unchanged, under the terms of use of Undum.

• The path to your game definition file. By convention, game definition files are named yourgamename.game.js.

In addition, from v.2 onwards, Undum supports defining Situations entirely within HTML. These situations are scanned and added to Situations defined in your Javascript Game Definition file, allowing you to have the best of both worlds. HTML Situations are discussed in the page on the HTML API.

## The Game Definition File

The game definition file where you create your game. To define a game you must provide the following data:

• A unique ID for the game, which is used to make sure saved games don't get confused.

• A version number that allows you to manage upgrades to your content.

• All the Situations that make up your game.

• The identifier of the situation that starts the game.

In addition it is very common to provide the following data:

• Descriptions of each quality your game will use, and how that should be displayed to the player.

• Definitions of what groups of qualities should appear in the character panel and what headings to use to label them.

• An Initialization function that sets up the game ready for playing. This is where you typically assign any starting qualities to the character, or set their initial character text.

And finally, there are a range of other data you can provide:

• Functions to be called whenever any situation is entered, or exited.

• Functions to be called before or after any action is carried out.

### Identifiers

Identifiers are small snippets of text that allow you to refer to something in Undum. There are two types of identifier. The Game identifier represents your whole game, and has its own particular requirements (described below).

Lots of other things in Undum have identifiers (Situations, Actions, Qualities, Quality Groups), and they all have the same requirements. These identifiers must consist of Latin lower-case letters (i.e. a-z, no accents), hyphens, and the digits 0-9 only.

### Game ID

The game identifier should be a string that is unlikely to be used in other games. You could use a UUID (my preference), or you could use a variation on your email mygame-myname@mydomain.com, or a URL you control http://mydomain.com/undum-games/mygame. If and when Undum games end up being re-distributable (as I hope they will), having a universally unique identifier will mean that saved games don't clash.

As stated previously, the game identifier doesn't have the same requirements as any other identifier in Undum, you can use any characters to make up your game ID.

### Version Number

The version number is a string of text that indicates what version of the content is in the file. There is no set format for this version text, so you can use any scheme that suits you. I have used the "major.minor" approach.

Like the Game ID, this value is used to make sure that saved games don't clash. If you change you content, then previous saved games may not work correctly. By updating the version number, you allow the player to be notified of this directly, rather than suffering a silent crash. The effect of this is that you don't need to update the version number if you make a change to something that doesn't alter the structure of the game. If you just change some text, for example, or add an extra action that merely outputs a piece of description.

### Situation List

Situations are defined in a Javascript object, placed in the undum.game.situations property. Situations in the object use their situation identifier as a property name, and a Situation object as its value. For example:

undum.game.situations = {
doorway: new Situation(...),
lobby: new SimpleSituation(...),
lobby-upstairs-closed: new MyCustomSituation(...),
... etc ...
};


The situation objects are described more fully below.

### Starting Situation

This is placed in the undum.game.start property. It should consist of the situation identifier as a string. It must be given.

### Qualities

Qualities don't have to be displayed to the user. They can just function as internal properties for use by your code. Qualities that will never be displayed don't need to be declared, you can just set them when you need them (we'll look at the API for setting qualities below).

Often you want the quality to be displayed, however, and so you need to tell Undum to display the quality, and how it should be formatted. The QualityDefinition object does that. Any quality that doesn't have a corresponding quality definition will be invisible to the player.

Quality definitions are placed in an object in the undum.game.qualities property. Within this object, the property names are the quality identifiers, and the values they contain are QualityDefinition objects. For example:

undum.game.qualities = {
investigation: new IntegerQuality("Investigation", ...),
"found-mr-black": new OnOffQuality("Found Mr. Black", ...),
... etc ...
};


There are a number of QualityDefinition constructors defined which automatically format in common ways, you can also define your own and take complete control of the output. We'll return to discussion of the API, below.

### Quality Groups

Qualities can be assigned to groups, and displayed under a common heading in the character panel. To define groups, place an object in the undum.game.qualityGroups property. This object should have properties which are the group identifiers, and values that are QualityGroup objects. For example:

undum.game.qualityGroups = {
stats: new QualityGroup(...),
clues: new QualityGroup(...),
equipment: new QualityGroup(...)
}


A common source of puzzlement is that you don't use this data structure to define which qualities belong in which group. Instead, each quality that you want to assign to a group, should be given the identifier of the group it belongs to. So your undum.game.qualities property will look something like:

undum.game.qualities = {
investigation: new IntegerQuality("Investigation", {group:'stats'}),
"found-mr-black": new OnOffQuality("Found Mr. Black", {group:'clues'}),
... etc ...
};


Again, see the API documentation below for more details about what you can pass into these constructors.

### Initialization Function

Your initialization function should be placed in the undum.game.init property. Normally its job is to configure the character at the start of the game. For example:

undum.game.init = function(character, system) {
character.qualities.investigating = 0;
character.qualities.money = 100;
... etc ...
system.setCharacterText(...);
};


Initialization functions can, but normally doesn't, output text. Instead the starting situation is tasked with outputting the initial content.

### Global Event Functions

Most of the time you want Situations to handle user interaction. Occasionally, however, you have to handle something that spans situations. It would be inconvenient to duplicate the same code in every situation. So Undum provides a set of hooks for you to respond globally to user interaction. There are five of these: enter, afterEnter, exit, beforeAction and afterAction. You can define functions in your game file using the properties: undum.game.enter, undum.game.afterEnter, undum.game.exit, undum.game.beforeAction, and undum.game.afterAction.

The enter, afterEnter, and exit functions look like this:

undum.game.enter = function(character, system, from, to) {
...
};


where from and to are the identifiers of the situations being left and entered, respectively. And the beforeAction and afterAction functions look like this:

undum.game.beforeAction = function(character, system, situation, action) {
...
};


where situation is the current situation identifier, and action is the identifier of the action being carried out.

These functions intentionally look like the enter, exit and act methods of the Situation object. These are described in more detail in the API reference.