CS 673: Spring 2012 Game Design and Programming

CS 673: Spring 2012

Game Designand Programming

(Game) Systems

System dynamics and systems literacy

2/14/2012 1Andy Nealen, Rutgers, 2012

Thinking in Systems

Donella Meadows

Andy Nealen, Rutgers, 2012 2/14/2012 2

“A system is a set of things—people, cells, molecules, or whatever—

interconnected in such a way that they produce their own pattern of

behavior over time.”

Donella Meadows


“A system is an interconnected set of elements that is coherently

organized in a way that achieves something.”

Donella Meadows



Elements

Interconnections

Function/Purpose

Elements

Visible, tangible things

Volatile, variable resources (oil, wood, etc.)

Macro: roots, trunk, branches, leaves

Micro: cells, vessels, fluids, chloroplasts

University: buildings, students, professors, etc.

Intangibles

University pride, academic prowess, etc.

Human preference, happiness, fun, fear, etc.


Interconnections

Cause and effect [If A, then B]

If [resource] is available, property costs rise

If fuel is used, character shrinks

Rules and policies are modeled this way

When interconnections change, the system may be greatly altered

Think of this as a graph

Changing connections changes graph topology


Function/Purpose

Fulfills a need/desire

So many successful systems in nature that we have no hand in (or should not have a hand in)

Explicitly designed systems need to live up to these standards

Time based (dynamic) behavior

Fluctuation of elements (tangible/intangible stock)

Self- sustainability and stability under uncertainty


More than the sum of its parts


Kinds of systems

Mechanical systems

Car motors, co-op/versus video/board games, etc.

Social systems

Neighborhoods, co-op/versus video/board games, etc.

Games are both mechanical and social


System graphs (1)


Stock. (resource) Memory of the history of changing flows in the system

Delays, buffers, shock absorbers of a system

System graphs (2)


System graphs (3)


Game example

(Simplified) Osmos system


Momentum

Size/mass

Food/motes



Momentum

Size/mass

Food/motes



Momentum

Size/mass

Food/motes

Stock

Tangible. size + food

Less tangible. Momentum

Osmos forms a closed system

Many games do this

But: also have a social layer/system

Feedback loops


“A feedback loop is a closed chain of causal connections, from a stock

through a set of decisions or rules or physical laws or actions that are

dependent on the level of stock, and back again through a flow to change

the stock.”

Donella Meadows


Balancing feedback loops

Aka “negative” feedback loops

Goal seeking or stability seeking

Mass spring systems (restoring spring forces)

Thermostat that tries to achieve target temperature

Cooling of hot beverage


Game example

Reinforcing feedback loops

Aka “positive” (or runaway) feedback loops

Lead to exponential growth or runaway collapses over time

Game example: chess

If I lose pieces, I am more likely to lose(and vice versa)


Game example


Momentum

Size/mass

Food/motes

Osmos

Reduction of size as momentum is added is a balancing feedback loop

Increase in size as motes are consumed is a reinforcing feedback loop

They need to be in balance (hard!)

Single stock + two balancing loops






Even simpler example: hot/cold shower

Does this look familiar?


Does this look familiar?


Time step in Euler integration

Depending on stiffness of ODE, smaller time step

rest length stretched

f(t) s(t)

s(t)

t

f(t) = k∙s(t)

t

Oscillations

Andy Nealen, Rutgers, 2012 2/14/2012 29t

Time step in Euler integration

Depending on stiffness of ODE, smaller time step

rest length stretched

f(t) s(t)

s(t)

t

f(t) = k∙s(t)To infinity!(eventually)

How to fix this? (1)






Dynamic perception

We need (spacetime) contrast to perceive difference and change… and explore

But thinking in spatio-temporal system dynamics is not trivial since cause and effect is not always obvious

We are linear minds in a non-linear world

Most relations are not linear

Examples. soil erosion, material behavior, etc.


Purpose/Meaning/Function


Purpose of a system

Procedural rhetoric (Ian Bogost)

Procedurality. creating, explaining, or understanding processes. And processes definethe way things work

Rhetoric. effective and persuasive expression

Dynamical meaning (Jon Blow, MIGS 2008)

Anytime we set up a system of behavior, that system communicates something to the player, whether intentional or not.


From Jon’s talk (1)


Video games are not a traditional storytelling medium per se. The player is an agent of chaos, making the medium ill-equipped to convey a pre-authored narrative with anywhere near the effectiveness of books or film. Rather, a video game is a box of possibilities, and the best stories told are those that arise from the player expressing his own agency within a functional, believable gameworld…

Steve Gaynor from his blog Fullbright,July 27th, 2008:

From Jon’s talk (2)


Frank Lantz (via email):

“...meaning which is less specific, less concrete and deliberate, harder to define, harder to pin down, a meaning that transcends the author-reader conduit model of ‘message’ style meaning, a meaning that absorbs intention but is not bound by it, a meaning that can't be reduced to a claim about the world, but is no less about the world because of it.”

Systems literacy

Analysis/redesign of existing systems

Hone ability to understand parts

See/understand interconnections

Ask “what if” questions about future behaviors

Be creative and courageous about system redesign

All of this becomes your toolbox as a designer

Find common abstractions of solved problems

We are amazing pattern recognizers. Use this!


Tweaking and redesigning

Numbers. Double or halve your parameters

Buffers. Sizes of stocks/resources

Stock/flow structures.

Delays. Delay between cause and effect

Balancing/reinforcing feedback loops.

Information flows. What to render and hide?

Rules. Interconnection policies

Structure. The interconnections themselves


Momentum in flOw is free (other interesting progress stucture though!)

Osmos system and flOw system


Momentum

Size/mass

Food/motes

Momentum

Size/mass

Food/motes

Guidelines

Get the beat of the system (playtest!)

Expose your mental models to others

Pay attention to everything, even intangibles and aesthetics, and try to get a feel for how they influence system (social/mechanical) dynamics

Implement feedback policies for loops based on experience and playtesting (!!!)


Further Reading

Meadows, Thinking in Systems

Hunicke et al., MDA

Salen/Zimmerman, Rules of Play

…

The world outside and all around you

Nope. Not kidding.

2/14/2012 42Andy Nealen, Rutgers, 2012

Documents

CS 673: Spring 2012 Game Design and Programming