Creative CommonsAttribution 3.0
creativecommons.org/licenses/by/3.0/
Interactivity & the Core Game Mechanic
Foundations of Interactive Game DesignProf. Jim Whitehead
February 6, 2008
Today’s Assignment
• Work Breakdown and Schedule‣ Due Today
• Have exams and game concept documents‣ Come up on stage after class to retrieve
Upcoming Assignments
•Busy week next week‣ Partially Operational Game Prototype
❖ Due Friday, February 15
❖ Need to have started your game
❖ Need to have at least some things working already
❖ Demonstration that you have spent at least 5-10 hours on your game already
‣ Progress Report❖ Also due Friday, February 15
❖ An update on where things stand in your schedule
❖ Is your project completing tasks on schedule, or falling behind?
Game Design Workshops
• Game Maker‣ Wednesdays, 6-8pm
‣ Engineering 2, room 180 (Simularium)❖ Enter on plaza level between E2 and JBE
• RPG Maker‣ Wednesdays, 5-7:15pm
‣ Engineering 2, room 280❖ 2nd floor, on front of building, on driving circle/Communications end (right side,
east end) of the building
❖ Arrive by 6pm to avoid external doors locking
❖ Knock on nearest door if late…
• CS 20/C# and XNA Game Studio Express‣ Thursdays, 4:30-7pm‣ Engineering 2, room 399 (third floor, by elevators)
Interactivity• What was the essential element of computer games that made
them so compelling, and allowed the industry to grow so quickly? ‣ Not video, audio, or text by itself, since these all predated video games by
many years
• Interactivity! ‣ Computing power makes this interactivity possible.
• “Just as the schwerpunkt of computers is processing, so too the schwerpunkt of all software is interactivity—and this goes double for games.”
• “Graphics, animation, sound, and music are all necessary to gaming, and they’re all important, but they’re not the schwerpunkt. Interactivity (sometimes called “gameplay”) is the real schwerpunkt of games.”
‣ Chris Crawford on Game Design, p. 74.
‣ Schwerpunkt: focal point, or, concentration of effort point, or, central point of attack
Definition of Interactivity
• Crawford uses a conversational metaphor • Interactivity is, “a cyclic process in which two active
agents alternately (and metaphorically) listen, think, and speak.” (p. 76)
• In computer games, the computer takes the role of one agent, and hence interactivity for video games becomes: ‣ “How can we program the computer to be an entertaining
conversational (metaphorically speaking) partner?” (p. 77)
‣ Computer must ❖ Listen well
❖ Give the player the opportunity to say anything relevant to the situation
❖ Must think well
❖ Must speak well
Interactivity Feedback Loop
• Can view a computer game as a kind of control system‣ Game creates output
‣ Player reacts to this output by making decisions and taking action❖ This generates one or more inputs
‣ Game reacts to these inputs, creating more outputs
game creates output
player makes internal decision
player takes action
Rules of Play, p. 316
High Interactivity
• What is high and low interactivity in a game? ‣ Is a fast-paced action game more interactive than a complex, slow-
moving strategy game?
‣ Not necessarily. If two people talk quickly, does that make their conversation more interactive?
• High interactivity comes when both sides are engaged in high-quality listening, high-quality thinking, high-quality speaking.
Assessing Interactivity in a Game
• Crawford states that you can estimate the interactivity level of any game by asking three questions: ‣ How much of what the player might desire to say does the game
permit the player to actually say?
‣ How well does the game think about the player’s inputs?
‣ How well does the game express its reactions?
Applying the Questions
• Fast-paced action game: ‣ Game allows player to say a limited number of words (move up,
down, left, right, fire, etc.)
‣ Player can say these words quickly
‣ Processing is simplistic: just move around on a map
‣ Expressiveness is complete, within the very limited confines of the world.
‣ Conclusion: small amount of interaction
Applying the Questions (2)
• Civilization ‣ Pace is slower, but player has wide range of things they can express
‣ Game executes complex set of algorithms.
‣ Listening and thinking are much deeper in this game
‣ Expressiveness is also quite high – many possible pieces to move, possible interactions among pieces
‣ Conclusion: Civilization is clearly a very interactive game
• OK, so are real time strategy games like Age of Empires or Empire Earth more interactive than Civilization?
Graphic Realism
• Crawford lists as a common mistake, “obsession with cosmetics” (p. 107)
• Five common motivations for putting good graphics and sound in a game: ‣ To further the gameplay
‣ To permit the player to show off the superior cosmetic capabilities of his new computer
‣ To show off the superior technical prowess of the programmer
‣ To keep up with the competition
‣ To provide the player with images and sounds that are intrinsically pleasing
• Crawford: The first reason is the only good reason for pursuing cosmetics.‣ Agree or disagree?
Process Intensity vs Data Intensity
• Process intensity is the degree to which a program emphasizes processes instead of data. ‣ Process is algorithms, equations, branches
‣ Data is reflected in data tables, images, sounds, text
• Analogies ‣ Language: nouns vs verbs
‣ Economics: goods vs services
‣ Computers: bits and cycles
Crunch per Bit Ratio
•“Because process intensity is so close to the essence of ‘computeriness,’ it provides us with a useful criterion for evaluating the value of any piece of software. That criterion is a vague quantification of the desirability of process intensity. It uses the ratio of operations per datum, which I call the crunch per bit ratio.” (Chris Crawford on Game Design, p. 89)
Core Game Mechanic
• To have interactivity, must have interaction from player‣ The player performs some action or actions....
‣ ... that intervene in the game world.
‣ Usually, one or more of these actions occurs very frequently, and is the dominant activity of the player
‣ This is the game’s core mechanic
• Core Game Mechanic‣ The essential play activity players perform over an over again
❖ Rules of Play, p. 316.
‣ When designing a game, an important question to resolve is:What does the player do?
‣ Your design is in trouble until you can crisply answer this question
❖ ...and the answer sounds like fun
Examples of Core Game Mechanic
• Breakout‣ Player turns knob on controller (or move lever of joystick) to move
paddle left and right
‣ Choose where ball hits on paddle to control movement of ball
Examples of Core Game Mechanic (2)
• Most platformer games‣ Player moves left and right, and jumps
‣ Avoid moving enemies
• Core game mechanic isn’t all of the kinds of interactions a player may have with a game‣ More focused: only the most frequent and important interactions
‣ In Kirby’s Adventure (NES), in additionto the typical moving and jumping,the core mechanic includes inhaling
Examples of Core Game Mechanics
• For most shmups, core game mechanic is:‣ Move to avoid enemies and position ship
‣ Firing at enemies
‣ Collecting powerups
‣ Different games can alter this.❖ In Radiant Silvergun,
part of the core mechanic is selectingwhich weapon to use
Perfect Cherry Blossom
Core Mechanic Discussion
• What is the core game mechanic in the following games?‣ Guitar Hero II
‣ Mass Effect
‣ Halo 2/3
‣ Ratchet & Clank: Future