f undamentals of g ame d esign c ore m echanics sayed ahmed bsc. eng. in csc. & eng. (buet) msc....
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FUNDAMENTALS OF GAME DESIGNCORE MECHANICS
Sayed AhmedBSc. Eng. in CSc. & Eng. (BUET)
MSc. in CSc. (U of Manitoba)
http://sayed.justetc.net
http://www.justETC.net
sayed@
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Presented at the University of Winnipeg, Canada
Just E.T.C for Business, Education, and Technology Solutions
CORE MECHANICS
Core Mechanics Determine how a game actually operates What are the rules of the game How the player interacts with them Defines the game play
TOPICS Understanding Core-Mechanics Designing Core Mechanics Explain the role of core mechanics in providing
entertainment How core-mechanics differ between real time and
turn based games How core mechanics are related to level design Key elements of core-mechanics
Resources, entities, and mechanics How you may use them to define rules precisely
Specific implementation of core mechanics In the internal economy of games
A set of mechanics that governs the flow of quantities How designers use mechanics
To create game play (challenges and actions)
TOPICS
How to design core mechanics By reexamining early design work Render it specific and concrete
Discuss random numbers How to use them in Games
FUNCTIONS OF THE CORE MECHANICS IN OPERATION
Operate the internal economy of the game Present active challenges Accept player actions Deter victory or loss Operate the Artificial Intelligence Switch the game from mode to mode Transmit triggers to the storytelling engine
FUNCTIONS OF THE CORE MECHANICS IN OPERATION
Operate the internal economy of the game Most important role of the core mechanics Specifies
how the game or player creates, distributes, and uses up the goods on which the game bases its economy
Present active challenges To the player via the user interface Active: governed by the core mechanics Passive: A chasm that the player must jump over
Accept player actions From the user interface Implement the effect on the game world
On other players as well
Detect victory or loss Detect condition for victory, loss, termination Detect success or failure in all challenges
and apply consequences
FUNCTIONS OF THE CORE MECHANICS IN OPERATION
Operate the Artificial Intelligence Operate the NPCs and artificial opponents
Switch the game from mode to mode Keep tracks of modes Changes game play mode Signal User Interface engine to update UI
Transmit triggers to the storytelling engine Trigger story telling engine to weave story
REAL-TIME GAMES VS. TURN-BASED GAMES
Real-Time Games Most games operate in real time
The game advances with time All players simultaneously play the game
In multiplayer games
Turn-Based Players Take Turns
Real-Time Core mechanics specify the parameters of a real world
that operates on its own whether the player acts or not
Processes operate continuously NPCs do and act what they are supposed to do Banks collect interest One shot event – may happen at players action only
REAL-TIME GAMES VS. TURN-BASED GAMES
Turn-Based Usually no NPC The core-mechanics do nothing until a player
take his turn Once a player is done the core mechanics can
compute the effect Then core mechanics remain idle until the next
player takes his turn You may define processes
But will only work in between players turn
CORE-MECHANICS AND LEVEL DESIGN
Level design What challenges each level will contain
Core-mechanics How challenges work in general But not exactly which challenges each level will
contain But sometimes you may cooperate with level
designers
KEY CONCEPTS
To design core mechanics You must document the different components
that define how your game works Find out the relationship among them
Resources Entities
Simple Entities Compound Entities Unique Entities
Attributes of Entities Mechanics
KEY CONCEPTS Resources
Types of objects or materials the game can move or exchange The game handles as numeric quantities May be also water – not countable
Does not refer to specific instances of these objects But the type itself
Core mechanics define the processes by which the game creates, uses, trades, and destroys resources
Rules by which Specific instances of resources
Can legally be moved from place to place Owner to owner Can come into and go out of the game
Non-physical concepts Popularity, resistance to poison as resources Try to quantify them as numbers so that you can manipulate them
KEY CONCEPTS
Entities Particular Instance of a resource State of some element – light – symbolic value Building, character, animal State of a traffic light Simple Entities
Specified by single value Score, state of a light Identify simple entities and define them in core mechanics
Compound Entities More than one data value to describe an entity Wind – speed and direction Each value = an attribute Avatar
A compound entity with another compound entity as attributes
KEY CONCEPTS
Entities Unique Entities
Only one entity of a particular type Avatar for example
Attributes of Entities An attribute is an entity that belongs to, and
therefore helps to describe, another entity Defining Entities for Your Game
Find out all entities in the game Define how to keep track of them Define how to represent them through user
interface Programmers will use these entities
KEY CONCEPTS
Mechanics Document how the game world and everything in it
behaves State
the relationships among entities The events and processes that take place among the
resources and entities of the game The conditions that trigger events and processes
Describe The overall rules of the game Behavior of particular entities
Operate throughout the game Apply only in particular gameplay modes Global Mechanic
Example: governs when the game changes from mode to mode (with help of entities that record what modes it is in)
RELATIONSHIPS AMONG ENTITIES
The value of one entity depends on the value of another entity They have a relationship Define it in your core-mechanics Numeric-entities: express mathematically Character levels
Experience points earned Character level = exp. Points * 1000
Events and Processes You state that something happens A change occurs Event
A specific change that happens once when triggered by a condition
KEY CONCEPTS
Events and Processes Process
A sequence of activities that once initiated continues until stopped
Conditions To define what causes an event to occur What causes a process to start or stop Conditional statements Define conditions in negative terms
Exception to general rules
Entities with their own mechanics Describe in terms of OOP
RELATIONSHIPS
Numeric Relationship is defined in terms of numbers and
arithmetic operations A bakery can bake 50 loaves of bread from one
sack of flour and four buckets of water Probability of an injury is directly proportional to
the weight and speed of the athletes Need familiarity with algebra and arithmetic
Symbolic What happens when a NPC sees the traffic light
to be Red, green, or yellow
INTEGRATION: NUMERIC AND SYMBOLIC RELATIONSHIPS
Your game may need to change the state of symbolic entities based on numeric entities
THE INTERNAL ECONOMY
An economy is a system in which resources and entities are produced, consumed, and exchanged in quantifiable amounts
Game designers: design and tune the game’s economy
Components Source Drains Converters Traders Production Mechanisms
Tangible and intangible resources Feedback loops, Mutual Dependencies, and Deadlocks Static and Dynamic Equilibrium
THE INTERNAL ECONOMY Source
A resource or entity can come into the game world where it was not before The mechanics by which it arrives is called source Enemies at the start, enemies spawn at different points
Each spawn point maintained by a mechanic Production rate Global mechanics Limited or Unlimited
Drains A mechanic that determines the consumption of resources Permanent drop out Shooting draining ammunition Being hit by enemy Consume, decay show a cause for draining
Converters Mechanic or entity Turns one or more resources into another type Production rate, input to output ratio Settlers: grain into flour, rate: one to one (bag) + 20 seconds
THE INTERNAL ECONOMY
Traders Mechanic that trades goods Stock trading game – financial construct, sword
trader Production Mechanisms
A class of mechanics that makes a resource conveniently available to a player
Sources that bring the resource directly into player’s hand
Characters to perform production Command & conquer
Tangible and intangible resources Tangible: Require physical space Intangible: No physical space required
THE INTERNAL ECONOMY
Feedback loops, Mutual Dependencies, and Deadlocks Need some input resources to produce
something Think about deadlock
Static and Dynamic Equilibrium
CORE MECHANICS AND GAME PLAY Challenges and the core mechanics
Passive challenges Not presented by core-mechanics – already there Can implement the actions, detection, and offer reward
Active challenges Offered by the core-mechanics A puzzle to open the door Define rules, actions, outcome
Actions and the Core Mechanics Player Actions Trigger Mechanics
Must specify a mechanic that implements each action in each gameplay mode
Initiate an event, start or stop processes Press a button, UI triggers a mechanic that implements the action,
mechanic – change the posture of the avatar – a symbolic attribute, determine and assign head position from ground
Actions Accompanied by Data Manipulation or storage of data Event mechanic and entity
CORE MECHANICS DESIGN
Goals of Core Mechanics Design Strive for Simplicity and Elegance Look for Patterns, then Generalize Don’t try to get everything perfect on paper Find the right level of detail Revisit your earlier design work
Answer questions such as what is the player going to do?
List your Entities and Resources Add the Mechanics Think About your resources Study your entities Analyze challenges and Actions Look for global mechanics
CORE MECHANICS DESIGN
Goals of Core Mechanics Design Strive for Simplicity and Elegance Look for Patterns, then Generalize Don’t try to get everything perfect on paper Find the right level of detail Revisit your earlier design work
Answer questions such as what is the player going to do?
List your Entities and Resources Add the Mechanics Think About your resources Study your entities Analyze challenges and Actions Look for global mechanics
RANDOM NUMBERS AND THE GAUSSIAN CURVE
Games use random numbers extensively Random numbers are usually generated as
>= 0 and < 1 In Statistics
Probabilities are always calculated between 0 and 1 You can use probabilities to
Generate events randomly Fix number of enemies Example: 10% times an event will happen
Generate a random number, if that’s <= 0.1 Execute the event
Weapon successful hit rating 80% (0.8) – to the aimed target Generate a random number, if that’s <= 0.8
Hit the target
PSEUDO-RANDOM NUMBERS
Random number generators (algorithms) usually use a seed If the seed is the same the sequence of the numbers
will be the same If a game always uses the same seed, the generated
numbers and the sequence will be the same all the time
Such numbers are called pseudo random numbers Useful for testing games
Bug fixing – can prevent bugs happening by chance Identify that changing the mechanics has affected the game
or not – fine tune core mechanics However, players play the game
Pseudo random numbers are not used Rather the seed is changed (current time), so that the
sequence of random numbers changes at each play
MONTE CARLO SIMULATION
You can test a system with two or few inputs easily Some direct mathematical relation may exist
But system that are dependent on too many factors May be hard to test Defining mathematical relationship can be difficult Still, using the mathematical relations to
understand and test the system may be difficult Rather you can take random input, and execute the
system, check the output Try to justify that the output makes sense or not If the output is logical or not If not, then you should work on more fine tuning
MONTE CARLO SIMULATION
A game tournament with 20 teams Difficult and time consuming
To make people play the game Test if the algorithms resemble fairness or not
Rather automate the game playing Select random inputs Analyze the output Think if the output made sense? Did the weak team defeat the strong team?
Did that happen very frequently – if so the game mechanics is not reasonable/fair – needs
fine tuning If it happened rarely – the game can be assumed to be
fair
UNIFORM DISTRIBUTION
Random numbers are generally generated with uniform distribution
The chance of getting any one number is exactly equal to getting any other number
Uniformly distributed die rolls Die roll = (random number * number of faces on
the die) + 1
NON UNIFORM DISTRIBUTION
You may want that Some values will be generated more frequently than
others For example,
You are designing a game: olympic shooting A player who came to play in olympics
Most of the times will hit a very close area• Than he will hit an area far from the center
An artificial player needs to be implemented that most of the times he hits a point close to the center
So the random number generation algorithm should Generate numbers where some numbers (the middle ones)
• Will show up more frequently than others Can be implemented as the sum of the numbers as
generated from Two or three dice rolls (at once) From two dice rolls: only one combination yields 2 but six
combinations (six possible ways) yield 7
THE GAUSSIAN CURVE
THE GAUSSIAN CURVE
Most things lie somewhere in the middle Rare things lie in the extremes
SUMMARY
By this time, you have a clear understanding of What core mechanics are What they do in games Mechanics consists of
Algorithms and data That governs the way the game is played
How to document core-mechanics In terms of
Resources, simple and compound entities Mechanics composed of
Events, processes, and conditions
Internal economy of games To define the movement of resources from
Place to place Owner to owner
Governed by mechnics
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