Design Fundamentals
of Stealth Gameplay
in the Thief series
Randy Smith
[email protected]
Design Fundamentals of Stealth Gameplay
in the Thief Series, [email protected]
Disclaimers
• I didn’t design Thief’s gameplay
»
»
»
»
Doug Church
Marc LeBlanc
Tom Leonard
Paul Neurath
»
»
»
»
Tim Stellmach
Greg LoPicollo
Dorian Hart
etc.
• This is about open-ended stealth
gameplay. Other games mentioned
are being evaluated by this standard
only.
Design Fundamentals of Stealth Gameplay
in the Thief Series, [email protected]
What is stealth in Thief ?
• Goal = move through space
» Steal
» Blackjack
» etc.
» Pick lock
» Pick pocket
• Failure = AI state becomes “alert”
» Combat
» Fleeing
Design Fundamentals of Stealth Gameplay
in the Thief Series, [email protected]
How does the AI become alert?
• The player has detectability
» Visibility (light gem = feedback)
» Audibility
• The AI has senses
» Seeing
» Hearing
• The overlap between player
detectability and AI senses…
» …is where the AI becomes alert or not
» …is where stealth happens
Design Fundamentals of Stealth Gameplay
in the Thief Series, [email protected]
Design Fundamentals of Stealth Gameplay
in the Thief Series, [email protected]
What is this lecture about?
• It is about stealth gameplay
»
»
»
»
Player movement through space
Player detectability
AI Senses
AI State
• It is not about:
» Goals (such as stealing)
» Consequences (such as combat)
Design Fundamentals of Stealth Gameplay
in the Thief Series, [email protected]
Let’s design a stealth game!
You are a thief in a medieval city. There is a
mansion in the distance, full of loot. A wall
separates you from the mansion, and a guard
patrols in front of the gate. A torch nearby
spills light across the area.
Do you:
A) Wait until the guard has his back turned
and run through the gate.
B) Put out the torch with a water arrow.
C) Sneak up on the guard through the
shadows and blackjack him.
Design Fundamentals of Stealth Gameplay
in the Thief Series, [email protected]
More stuff this lecture is about:
• It is not about:
» Stealth flavored gameplay
» How gameplay is qualified (what makes
stealth gameplay stealth gameplay??)
» What is the definition of “open-ended”
gameplay?
» Discrete interaction
• It is about:
» Player expression
» Analog interaction
Design Fundamentals of Stealth Gameplay
in the Thief Series, [email protected]
Major concepts for this lecture
• Discrete Interaction Structures
» Exemplified by Choose-Your-OwnAdventure books
• Analog Interaction Structures
» Exemplified (for the sake of this
presentation) by Quake or other FPS
Design Fundamentals of Stealth Gameplay
in the Thief Series, [email protected]
Design Fundamentals of Stealth Gameplay
in the Thief Series, [email protected]
Qualities of Discrete
Interaction Structures
• Finite, enumerable choices offered to the
player.
• Player must choose one of the available
options, not something in-between, not
invent their own thing.
• Designer must explicitly create all
interaction for the player.
• Should be called “Choose Someone Else’s
Adventure”
Design Fundamentals of Stealth Gameplay
in the Thief Series, [email protected]
Design Fundamentals of Stealth Gameplay
in the Thief Series, [email protected]
What are Analog Interaction
Structures?
• Rough Definition: A collection of
player-influenced, interacting game
systems
• An abstract design tool for
(de)constructing open-ended
gameplay and analyzing relevant data
• A “unified theory” of existing thought:
» Simulation vs. Emulation
» Player Tools
» Partial Failure
Design Fundamentals of Stealth Gameplay
in the Thief Series, [email protected]
» Feedback
» etc.
What are analog interaction
structures NOT ?
• The only way to think about,
construct, or deconstruct any type
of gameplay
• Necessarily the most useful tool for
the job
• A ton of brand new thought
Design Fundamentals of Stealth Gameplay
in the Thief Series, [email protected]
A Useful Metric
• To what extent can the designer
predict the player’s experiences?
» A lot, the player can not take any action
the designer did not explicitly implement
and intent  Discrete Interaction
» Not much, really, the player has nearinfinite ways to overcome the game’s
challenges  Analog Interaction
Design Fundamentals of Stealth Gameplay
in the Thief Series, [email protected]
Analog Expression: Player
Movement in Quake
• Data relating to player movement:
»
»
»
»
Player
Player
Player
Player
location (X,Y,Z)
orientation (H, P)
velocity vector
acceleration vector
• Player expression:
» Accelerate in various directions
» Look right, left, up, down, or combo
» Some fancy movement (jump, duck, etc.)
Design Fundamentals of Stealth Gameplay
in the Thief Series, [email protected]
What makes it “analog”?
• Hey, yea! There aren’t analog
variables – so theoretically, all
possible states are enumerable.
• ...but the player cannot “choose”
their movement data. There is no
“choice”.
• Instead, the player uses movement
tools to set or “express” their
desired movement data.
Design Fundamentals of Stealth Gameplay
in the Thief Series, [email protected]
Player movement is relevant to
Quake’s core gameplay
• Player movement data is critical to
resolving combat from moment to
moment:
» Orientation is how you aim weapons
» Movement is how you dodge, take cover,
charge, etc.
» These are examples of the player
expressing “higher order concepts”
Design Fundamentals of Stealth Gameplay
in the Thief Series, [email protected]
Design Fundamentals of Stealth Gameplay
in the Thief Series, [email protected]
Design Fundamentals of Stealth Gameplay
in the Thief Series, [email protected]
What else does Quake have?
• For both Player and Enemies:
» Movement
» Weapons that fire projectiles
» Damage model (hit points)
• Projectiles
• A game world with physics
simulation.
» Collisions between player, terrain,
projectiles.
Design Fundamentals of Stealth Gameplay
in the Thief Series, [email protected]
Components to Analog
Interaction Structures
• A game world that hosts interactions
dictated by simulations (in Quake,
physics in the 3D world)
• Analog player expression (in Quake,
player movement)
• Analog/partial failure (in Quake, hit
points)
• Player tools to take arbitrary actions (in
Quake, weapons that fire projectiles)
Design Fundamentals of Stealth Gameplay
in the Thief Series, [email protected]
Design Fundamentals of Stealth Gameplay
in the Thief Series, [email protected]
Let’s talk about Thief already
• Game world that hosts interactions
dictated by simulations = 3D world,
similar to Quake
»
»
»
»
Physics
Line-of-sight (LOS)
Lighting, light sources
Sound propagation, noisy surfaces
Design Fundamentals of Stealth Gameplay
in the Thief Series, [email protected]
Design Fundamentals of Stealth Gameplay
in the Thief Series, [email protected]
Design Fundamentals of Stealth Gameplay
in the Thief Series, [email protected]
Analog Expression in Thief
• Player movement
»
»
»
»
Player
Player
Player
Player
location (X,Y,Z)
orientation (H, P)
velocity vector
acceleration vector
• Player movement expression
» Accelerate in various directions
» Look right, left, up, down, combo
» Some fancy movement (jump, climb, etc.)
Design Fundamentals of Stealth Gameplay
in the Thief Series, [email protected]
Design Fundamentals of Stealth Gameplay
in the Thief Series, [email protected]
Design Fundamentals of Stealth Gameplay
in the Thief Series, [email protected]
Design Fundamentals of Stealth Gameplay
in the Thief Series, [email protected]
Design Fundamentals of Stealth Gameplay
in the Thief Series, [email protected]
Higher Order Concepts in
Expressing Stealth
• Hide in shadows = move into a dark
part of the world
• Move silently = avoid moving over
loud surfaces, move slowly
Design Fundamentals of Stealth Gameplay
in the Thief Series, [email protected]
Design Fundamentals of Stealth Gameplay
in the Thief Series, [email protected]
Design Fundamentals of Stealth Gameplay
in the Thief Series, [email protected]
Quake with only 1 hit point
• No partial / analog failure
• A lot of the data becomes much less
relevant to resolving combat:
» How damaging weapons are
» Player’s emergent combat tactics when
they are weak versus when they are
healthy
Design Fundamentals of Stealth Gameplay
in the Thief Series, [email protected]
Design Fundamentals of Stealth Gameplay
in the Thief Series, [email protected]
Design Fundamentals of Stealth Gameplay
in the Thief Series, [email protected]
Design Fundamentals of Stealth Gameplay
in the Thief Series, [email protected]
Design Fundamentals of Stealth Gameplay
in the Thief Series, [email protected]
Stealth-related tools in Thief
• Potions
» Invisibility
» Speed
• Thrown tools
» Flashbomb
• Arrows
» Water arrow
» Moss arrow
» Noisemaker arrow
Design Fundamentals of Stealth Gameplay
in the Thief Series, [email protected]
Design Fundamentals of Stealth Gameplay
in the Thief Series, [email protected]
Design Fundamentals of Stealth Gameplay
in the Thief Series, [email protected]
Design Fundamentals of Stealth Gameplay
in the Thief Series, [email protected]
Design Fundamentals of Stealth Gameplay
in the Thief Series, [email protected]
Design Fundamentals of Stealth Gameplay
in the Thief Series, [email protected]
Analog Interaction Structure
chart = a data analysis tool
• Useful for thinking about data:
» What data the player has input into
» How data flows from system to system
and eventually leads to success or failure
• Drawing the chart is as much art as
science
» Which data boxes?
» How many arrows?
» Draw the chart differently to analyze the
data differently
Design Fundamentals of Stealth Gameplay
in the Thief Series, [email protected]
Feedback in Thief
• AI State and AI Senses
» Broadcast speech
» Animations
» Behavior
• Player Visibility / Audibility
» Light gem
» Listening
• AI Movement
» Player senses
Design Fundamentals of Stealth Gameplay
in the Thief Series, [email protected]
Design Fundamentals of Stealth Gameplay
in the Thief Series, [email protected]
Level-building for Analog
Interaction
• Don’t create “scripts”
» Don’t plan the player’s experiences for
them.
• Create “possibility spaces”
» Populate the world with challenges
» Populate the world with things that
interact with the player’s tools, the
simulations, manipulate the data flow
» Avoid absolutes, embrace gradients
Design Fundamentals of Stealth Gameplay
in the Thief Series, [email protected]
Design new types of analog
gameplay!
• A game world that hosts
interactions dictated by simulations
• Analog player expression
• Analog failure
• Player tools to take arbitrary actions
Design Fundamentals of Stealth Gameplay
in the Thief Series, [email protected]