Information / Cybernetics

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Information / Cybernetics. Robin Burke GAM 224 Winter 2008. Outline. Reaction Papers Probability and Information Theory Cybernetics Feedback loops Homework #2. Admin. 1 st Reaction paper due Tuesday For maximum credit use some idea from the book look for an information economy - PowerPoint PPT Presentation

Text of Information / Cybernetics

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Information /CyberneticsRobin BurkeGAM 224Winter 20081OutlineReaction PapersProbability and Information TheoryCyberneticsFeedback loopsHomework #22Admin1st Reaction paper due TuesdayFor maximum credituse some idea from the booklook for an information economyfeedback loopsa system of signs for the playeretc.

3UncertaintyMany games are probabilisticroll the diceshuffle the cardsSome games are notChessCheckersDots and Boxes4Certainty vs uncertaintyCertaintythe condition when the outcome of an action is known completely in advance.Some games operate this wayChessDots and BoxesBut even thenuncertainty about who will winotherwise what is the point?5ProbabilityProbability is the study of chance outcomesoriginated in the study of gamesBasic ideaa random variablea quantity whose value is unknown until it is "sampled"the random variable has a distributionfor each possible valuea probability that the value will occur6Single DieRandom variable# of spots on the side facing upDistribution1...6each value 1/6 of the timeSame event, different random variableodd or even # of dots7Two diceRandom variablesum of the two die valuesDistribution2, 12 = 1/363, 11 = 1/184, 10, = 1/125, 9 = 1/96, 8 = 5/367 = 1/6Non-uniformnot the same as picking a random # between 2-12dice games use this fact8Role of ChanceChance can enter into the game in various waysChance generation of resourcesdealing cards for a game of Bridgerolling dice for a turn in BackgammonChance of success of an actionan attack on an RPG opponent may have a probability of succeedingChance degree of successthe attack may do a variable degree of damage9Role of Chance 2Chance changes the players' choicesplayer must consider what is likely to happenrather than knowing what will happenChance allows the designer more latitudethe game can be made harder or easier by adjusting probabilitiesChance preserves outcome uncertainty with reduced strategic inputexample: Thunderstorm10PsychologyPeople are lousy probabilistic reasonersWe overvalue low probability events of high risk or rewardExample: Otherwise rational people buy lottery ticketsWe assume success is more likely after repeated failureExample: "Gotta keep betting. I'm due."Impacts for game design

11Information TheoryThere is a relationship between uncertainty and informationInformation can reduce our uncertaintyExampleThe cards dealt to a player in "Gin Rummy" are private knowledgeBut as players pick up certain discarded cards from the pileIt becomes possible to infer what they are holding12Information Theory 2Classical Information TheoryShannonInformation as a quantityhow information can a given communication channel convey?compare radio vs telegraph, for examplemust abstract away from the meaning of the informationonly the signifier is communicatedthe signified is up to the receiverInformation is measured in bitshow many choices the receiver must choose from in interpreting the message13NoiseNoise interrupts a communication channelby changing bits in the original messageincreases the probability that the wrong message will be receivedRedundancystandard solution for noisemore bits than required, ormulti-channel

14ExampleLegend of Zelda: Minish CapMonsters are not all vulnerable to the same types of weapons10 different weapons(we'll ignore combinations of weapons)Encounter a new monsterwhich weapon to use?4 bits of unknown informationWe could try every weaponbut we could get killed15Example, cont'dMessagesthe monster iconography contains messagesrocks and metal won't be damaged by the swordflying things are vulnerable to the "Gust Jar"etc.the game design varies the pictorial representations of monstersknowing that these messages are being conveyedlearning to interpret these messagesis part of the task of the playeronce mastered, these conventions make the player more capableOften sound and appearance combinea redundant channel for the information16Information FlowPeople exchange information with a game systemto figure out options and outcomesBut a game system can use information flow internally as wellNorbert Weiner developed cybernetics to explain this type of systemCybernetics is an attempt to unify the study of engineered and natural systems17Cybernetic SystemsCybernetics is about controlHow is the behavior of a system controlled?Control implies that there are parameters that should be maintainedExample: temperaturehuman bodycar engineControl implies informationTemperature messages"too high""too low""OK"

18Feedback LoopsBasic loopA cybernetic system needs a sensor that detects its stateThe information detected by the sensor is then compared against the desired valueIf the value is not correct, the system adjusts its statethe sensor detects this new state, etc.The system maintains stability by feeding the information about its state back to the process producing the state19Two Types of Feedback LoopsNegative Feedback Loop"inhibition"As the state changes, the loop acts to move it in the direction of its previous stateExamplethermostatpendulumPositive Feedback Loop"excitation"As the state changes, the loop acts to move it in the direction that it is movingExampleautomobile turbochargerhome team advantage20Feedback Loops in GamesFrom bookgame statescoring functioncontrollergame mechanical bias21Example 1game statedistribution of dice among playersscoring functionnumber of unsuccessful challenges / bluffscontrollerfor each failure, lose a diebiasless information about game statemore likely to bid unsuccessfully22Effects?23Example 2game statestate of a fighting gamescoring functionplayer's healthcontrollernear-KObiasincrease chance of critical (high damage) hit on opponent24Effects?25Example 3game statestate of the chessboardscoring functionthe number of pieces takencontrollerfor each piece takenbiasadd that piece to the taker's side in any positionJapanese Shogi has a rule like this26Effects?27ExamplesMario Kart28Multiple LoopsGames may have multiple feedback loops in operationExamplesracing gamea player who falls behind may be better power-upsAI racers may adjust their ability to keep pace with playerRPGkilling monsters gives experience points for gaining levelsas a player gains levels, they gain better weapons and greater abilitiesmore success at killing monsters, etc.butgame is designed so advanced areas have tougher monsterslevels get farther and farther apart29In GeneralNegative feedback loopsincreases system stabilitymakes the game last longermagnifies late successesPositive feedback loopsdestabilizes the systemmakes the game shortermagnifies early successPositive feedback is usually essentialpropels a player to victoryotherwise, game can go on foreverone reason that three-player games are difficult to design30The Other SenseWe also use the word "feedback" to meanpraise vs criticism"I got some negative feedback on the proposal, so I'm revising it."This is not the samepsychological sense of feedbackinformation about the quality of somethinggood or badcybernetic sense of feedbacka dynamic established by a system's structure that pushes its state in one direction or anotherin response to information31Game Design IssuesImportantWe are talking about the system internallynot the game + user systemKnow what feedback is going on in your systemanalyze how game mechanisms combine to produce feedbackFeedback may be undesirablenegative feedback may make a successful player feel punishedpositive feedback may magnify ability differences between players32Example gameCrazy Eightsdeal 8 cardsturn up top card of stockEach playermust follow suit or rankor draw from pileFirst one out of cards winsSpecial cards8 changes suitA changes direction2 = draw 233Play34Homework #2Crazy Eights rules +Players with 4 or fewer cards can use a King to change suitand lay down a card at the same timeFeedback effect?35Play36Homework #2 cont'dHomeworkrestabilize the gameleave these rules as ischange the game to be more faircountervailing negative feedbackbut game can't go on foreverTwo stagesRule Set #1 -> Playtest #1Rule Set #2 -> Playtest #2Due 1/2937TuesdayConflictReaction paper #1Read: Chapter 2038