FUNDAMENTALS OF GAME DESIGN, SECOND EDITION
Add the Mechanics
With your list of entities and list of verbs, you're ready to start defining the mechanics. Again reread your earlier design work. If any sentence includes or implies the word somehow, now is the time to define exactly how. "The player gets money" or "gets money somehow" must turn into a precise specification of when the player's money entity increases and by what amount.
As you read, remember that mechanics consist of relationships, events, processes, and conditions.
Start with any resources that you identified in the previous step and think about how they flow through the game. What sources bring them into the game? What drains remove them? Can they be traded or converted automatically into another resource? Every source, every drain, and every conversion requires mechanics that determine how a conversion operates, when, and at what rate. Also ask yourself what happens when the resource runs out. If nothing much changes, you may not need the resource. Because a resource is a general concept rather than a specific quantity like an entity, you may be able to determine a lot about a resource's mechanics just by thinking through the resource flow in the economy.
Remember that games that don't deal in numeric quantities don't have resources. Such games contain only symbolic entities.
Once you have a good grasp of your resources' sources, drains, and conversions, move on to your entities. Go down your list of entities and ask the following questions about each one:
■ Does this entity store an amount of a resource, and if so, have I already documented how it works in the previous step?
■ What events, processes, and relationships affect the entity? What conditions apply to these events, processes, and relationships?
■ What events, processes, and relationships does the entity contribute to? What conditions apply to them?
■ What can the entity do by itself, if anything? Any entity that can do something by itself—whether the entity is as simple as a detector or as complicated as an NPC—requires mechanics to define what it does and how.
■ What can the player do to the entity, if anything? If the player can manipulate the entity, he requires an action to do so, and actions require mechanics.
■ Is this a symbolic entity? If so, it requires mechanics to control how the entity gets into each of its possible states.
Many of the verbs in your list of verbs will be associated with particular entities, so as you examine an entity, check to see which verbs apply to it and what mechanics they imply.
ANALYZE CHALLENGES AND ACTIONS
Go over the list of challenges and actions that you intend to offer in each gameplay mode. All the active challenges and each action must have an associated mechanic and possibly some associated data. (If it requires data, you should already have an entity defined for it.) How does the action affect the world? How does the challenge affect the avatar or the other entities under the player's control? Use the answers to these questions to document your mechanics.
Global mechanics operate all the time, regardless of what gameplay mode or level the game may be in. Global mechanics include those that implement actions such as pausing the game or, if the player can win or lose in more than one gameplay mode or level, detecting the victory or loss conditions. (In many games, the level designers specify a different victory condition for each level, but the loss condi - tions—such as running out of money or health—remain the same in every level.) Go through your list of verbs and see how many of them describe global mechanics, and then define how each works.
