Lecture 4 CS170: Game Design Studio 1

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Lecture 4CS170 Game Design Studio 1

• UC Santa Cruz
• School of Engineering
• www.soe.ucsc.edu/classes/cmps170/Fall2008
• michaelm_at_cs.ucsc.edu
• 06 October 2008

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Core Mechanics

• Core mechanics the precise definition of the
  rules by which the game state changes over time
• Example
• Vague rule Players will be penalized for taking
  too long to get through the swamp.
• Core mechanics When the avatar enters the
  swamp, the black toadstools begin to emit a
  poison gas that the player can see filling the
  screen, starting at the bottom and raising at a
  rate of one game-world inch every three seconds
  by the end of 3 minutes, the gas will reach the
  height of the avatars face, and if by that time
  the avatar is still in the swamp, the avatar
  dies. If the avatar returns to the swamp later,
  the gas will be gone, but the process will star
  over again from the beginning.
• The purpose of physical prototyping youve been
  doing is to force you, in an inexpensive way, to
  experiment with detailed core mechanics
  specifications
• Core mechanics are described in
• The design doc
• Prototypes (on paper and in code)
• The finished game (in code)

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Functions of core mechanics

• Operate the internal economy of the game
• Resource production, consumption
• Present active challenges to the player, as
  specified by level design
• Passive challenges have mechanics to describe
  player action, but not the challenge itself
• Accept player actions from the interface and
  implement their effects
• Operate the AI
• Switch the game from gameplay mode to gameplay
  mode
• Transmit triggers to storytelling engine when
  dramatically significant events occur

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The world

• The core mechanics define what happens in a
  living, real-time world, even when the player
  isnt doing anything
• In a turn-based game, core mechanics dont do
  anything until the player does something
• Processes operate continuously for extended
  periods
• Events are one-shot mechanics that trigger
  because of player action, or because a special
  condition has been detected in a process
• Turn based games tend to be constructed primarily
  of events
• The process part of turn-based games are all the
  updates that the player or game masters have to
  do after every turn for all the
  non-player-controlled entities

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Level design

• The core mechanics define how different
  challenges actually work
• Level design specifies, in a data driven way, the
  type, timing and sequence of challenges that
  should appear during play
• Mechanics read the data to instantiate the
  sequence of challenges defined in the data
• If levels are generated, core mechanics include
  how to generate levels (select and sequence
  challenges)

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Resources

• A resource is a type of object or material that a
  player can move or exchange
• Handled internally as a numeric value
• Core mechanics are responsible for defining how
  resources are created, and used up
• Lets think of some examples of resources
• Health and mana
• Ammunition, keys, gold, food, health packs
• Time

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Entities

• Entities represent elements in the gameworld
• Simple entities consist of nothing but a single
  attribute
• Score
• Traffic light
• Compound entities have multiple attributes
• Entities correspond to what programmers tend to
  think of as the objects (in an object-oriented
  sense) within a gameworld
• The engine itself will often be factored into
  some object hierarchy these are not entities in
  the game design sense because they are not part
  of the gameworld
• Mechanics specify the relationships between
  entities and entity attributes how attributes
  change over time as a function of player actions
  and the values of other attributes

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Internal economy

• The internal economy is the system in which
  resources and entities are produced, consumed and
  exchanged in quantifiable amounts
• Sources the mechanics by which a resource
  enters the world
• Spawn points
• Limited vs. unlimited
• Automatic sources (production rates)
• Drains the mechanics that determine the
  consumption of resources
• Shooting using ammunition
• Destroying enemies
• Decay

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Internal economy 2

• Converter mechanics that convert one resource
  type into another
• Traders mechanics that govern the trading of
  resources between players and the game
• Trading causes a reassignment of ownership
• Production mechanisms mechanics that make
  resources conveniently available to the player
• A special type of source under the control of the
  player
• Tangible vs. intangible resources
• If a resource is not directly represented in the
  game world, it is intangible. Money is a typical
  intangible resource

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Deadlock

• Be careful to avoid resource deadlock
• This can happen whenever theres a dependency
  loop among the resources in a game
• Example In Monopoly, you need money to purchase
  land in order to earn money (by rent). Need a way
  to bootstrap this is the purpose of the source
  mechanic involving Go (collect 200 dollars)
• Make sure that you provide mechanisms to the
  player to break deadlock
• Example In Settlers III, you need stone to
  create a stonecutters hut. You need a
  stonecutters hut to produce stone (to build
  buildings in general). Player starts with a small
  amount of stone. If she uses it all up building
  other buildings, can end up in deadlock. Settlers
  III avoids this by letting player tear down
  existing buildings to get stone.

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Equilibrium

• Static equilibrium if the player does nothing,
  system achieves a steady state
• Dynamic equilibrium if the player does nothing,
  system achieves an oscillating (repeating) state
• Its hard for players to reason about dynamic
  equilibria
• Many games dont achieve an equilibrium, but run
  down (slowly) if the player takes no action
• The player should always have to do something to
  achieve growth

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Level of detail

• The right level of detail for describing
  mechanics on paper strikes a balance between
  trying to nail down everything completely (youll
  drive yourself crazy) and leaving too much
  unspecified
• Use the most detail for uncommon (unfamiliar
  mechanics)
• Prototypes and spreadsheets can be the best way
  to capture super-detailed mechanics
• Its better to put something down and be wrong,
  than to leave something unspecified
• Specify mechanics in writing
• Implement in a prototype and experiment
• Iterate

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Designing mechanics

• Come up with lists of nouns and verbs from
  high-level design documents (e.g. pitch
  documents)
• List entities and resources based on noun lists
• Does a noun represent a resource, and entity an
  attribute, or none of these (for none of these,
  cross off the noun its irrelevant to the
  mechanics)
• Add mechanics to relate entities (look at verb
  list to get you started)
• Refine internal economy
• Define sources, drains, trading and conversion
  for resources
• Think about what happens when the resource runs
  out (if it deserves to be a resource, something
  should happen)
• Refine entities
• Analyze challenges and actions (define mechanics
  for them)
• Look for global mechanics