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SE 350 – Programming Games

Lecture 12: Core MechanicsLecturer: Gazihan Alankuş

2/10/2012

Today’s Lecture is Different

• We will learn about elements of core mechanics• We will identify them in your game ideas• I expect you to think and participate• We won’t finish all of them today

• Some slides have questions. Ask them to yourself afterwards and answer them. – This will help you improve your game.

Core Mechanics

• Space• Objects, attributes and states• Actions• Rules and Goals• Skill• Chance

[Jesse Schell, The Art of Game Design]

Rethink your game idea with these in mind

Keep these in mind while improving your game

Core Mechanics

• Space• Objects, attributes and states• Actions• Rules and Goals• Skill• Chance

Space

• Where things exist– Discrete vs. continuous– Dimensions (2D, 3D)– Bounded areas, connected or not– Nested spaces

• Most of your games are continuous• 2D and 3D

Questions: Space

• Is the space discrete or continuous?• How many dimensions?• What are the boundaries?• Are there sub-spaces? (other scenes)• Are there multiple ways of modeling your

game’s space?

Core Mechanics

• Space• Objects, attributes and states• Actions• Rules and Goals• Skill• Chance

Objects, Attributes and States

Object

Attribute

Attribute

Attribute

Value

Value

Value

Implemented as variables in components

Example

Ghost in Pac-Man

Position

Objective

Direction

(100, 200)

Avoid Pac-Man

left

(state machine)

Object Attribute Value

Secrets?

Questions: Objects, Attributes and States

• What are the objects in the game?• What are their attributes?• What are the possible states for each

attribute? – How do attributes change state?

• Any secret attributes?

Core Mechanics

• Space• Objects, attributes and states• Actions• Rules and Goals• Skill• Chance

Actions

• What can players do?– “Verbs” of game mechanics

• Operative actions– Move a checker forwards

• Resultant actions (more strategic actions)– Force the opponent to make an unwanted move

Actions: Emergent Gameplay

• Interesting resultant actions that emerge out of users’ behaviors– Identify them, nurture them

• Tips to support this– Add more verbs– Make verbs act on many objects– Goals can be achieved more than one way– Multiple avatars– Actions that change constraints

Questions: Actions

• What are the actions?– Which ones are operative?– Which ones are resultant?

• What objects do they act on?• How many ways can players achieve their goals?• Can users change constraints?• What resultant actions do you want to see?• Are you happy with resultant/operative ratio?• What actions do players wish they could do?– Can you enable them as operative or resultant?

Core Mechanics

• Space• Objects, attributes and states• Actions• Rules and Goals• Skill• Chance

Rules

• Tie together – Space– Objects– Actions– Consequences of actions– Constraints on actions

Goals• You can’t just tell them to do something unless

you set up the rules to favor it

Parlett’s Rule Analysis

Goals

• Concrete, understandable• Achievable• Rewarding

• Short-term• Long-term• Series of goals

Questions: Rules and Goals

• What are the foundational rules? • What are the related operational rules?• Are there different modes for rules?• What is the ultimate goal?– Is it clear?

• Are different goals related to each other in a meaningful way?

Core Mechanics

• Space• Objects, attributes and states• Actions• Rules and Goals• Skill• Chance

Skill

• Users’ levels of ability• Categories– Physical skills• DDR, guitar hero

– Mental skills• Puzzles

– Social skills• Most multiplayer games

Skill

• Balance difficulty and skill for best experience

Questions: Skill

• What skills does my game require from user?• Are there categories of skill that I’m missing?• Which skills are dominant? • Are these skills creating the experience that I

want? • Does the game demand the right level of skill?

Core Mechanics

• Space• Objects, attributes and states• Actions• Rules and Goals• Skill• Chance

Chance

• Things happening randomly in the game• Uncertainty -> Surprises -> Good!• A simple random function may not be enough

Uniform Gaussian

Chance

Random seed

Always different values

Fixed seed Same sequence of values

Randomization in Unity• Random.seed: if you give the same seed you get the same

sequence of values• Random.value: Get a uniform random value in [0, 1]• Random.insideUnitSphere: Get a Vector3 inside a sphere with

radius 1 • Random.insideUnitCircle: Get a Vector2 inside a circle with

radius 1 • Random.onUnitSphere: Get a Vector3 on the surface of a sphere

with radius 1• Random.rotation: Get a random rotation as a quaternion• Random.Range(min : float, max : float): Get a random value in

[min, max] • Random.Range(min : int, max : int): Get a random value in [min,

max)

Getting Chance Right is Tricky

• Calculate probabilities• Make sure undesirable edge cases do not

happen

Risk Taking

• Expected probability vs. trust in own skill• Example– Monsters appear randomly– What are the odds of me

killing a monster if one would find me in that room?• High? -> will risk going in• Low? -> will not risk

Questions: Chance

• What in your game is truly random? – What parts just feel random?

• Does randomness give– Positive feelings (excitement and challenge)– Negative feelings (hopelessness and lack of control)

• Would changing my probability distribution curves improve my game?

• Do players have a chance to take interesting risks in the game?

Core Mechanics

• Space• Objects, attributes and states• Actions• Rules and Goals• Skill• Chance

• Rethink your game idea with these in mind• Ground your decisions with these• Later in your presentations inform us how

they influenced your designs