Pac-Man - Revision history

Dave Mark: /* Architectures */

2011-07-15T22:04:42Z

Architectures

Dave Mark: /* Behavior Modes */ Changed section title to Architectures and moved some wording around.

2011-07-15T22:04:02Z

Behavior Modes: Changed section title to Architectures and moved some wording around.

Dave Mark: /* Post-Mortem */

2011-07-15T19:05:38Z

Post-Mortem

Dave Mark: /* External Links */

2011-07-15T19:01:35Z

External Links

Dave Mark at 18:47, 15 July 2011

2011-07-15T18:47:47Z

Dave Mark: /* Behavior Modes */

2011-07-15T18:41:12Z

Behavior Modes

Dave Mark: Corrected "scatter" behavior, added reference link

2011-07-15T18:33:31Z

Corrected "scatter" behavior, added reference link

Dave Mark: More detail on post-mortem

2011-07-15T17:49:49Z

Dave Mark: hooked up image

2011-07-15T15:38:57Z

hooked up image

Dave Mark at 15:34, 15 July 2011

2011-07-15T15:34:45Z

@@ Line 37: / Line 37: @@
 ==Architectures==
-Pac-Man uses a very simple [[finite state machine]] to control the behavior of the ghosts. The ghosts have 4 behavior states that they can be in. The ghosts spend most of their time in either "[[#scatter|scatter]]" or "[[#chase|chase]]" mode. When the player has eaten a power pill, the ghosts change to "[[#frightened|frightened]]" mode. After being eaten by Pac-Man, the ghosts switch to "[[#respawn|respawn]]" until they have returned to their base.
+Pac-Man uses a very simple [[Finite State Machine|state machine]] to control the behavior of the ghosts. The ghosts have 4 behavior states that they can be in. The ghosts spend most of their time in either "[[#scatter|scatter]]" or "[[#chase|chase]]" mode. When the player has eaten a power pill, the ghosts change to "[[#frightened|frightened]]" mode. After being eaten by Pac-Man, the ghosts switch to "[[#respawn|respawn]]" until they have returned to their base.
 They switch between chase and scatter happens on a fixed timer. The amount of time spent in each mode is different for each level with the bias being towards chase mode as the levels increase. The result of alternating between these two modes is that there is an ebb and flow to the interactions with the ghosts. This was by design as explained by creator, Tōru Iwatani.

@@ Line 36: / Line 36: @@
 Note that there is no decision made at the intersections ''other'' than how to get to the current target tile. Therefore, this phase can adequately be compared to [[steering behaviors]].
-==Behavior Modes==
+==Architectures==
-The ghosts have 4 behavior [[Finite State Machine|states]] that they can be in. The ghosts spend most of their time in either "[[#scatter|scatter]]" or "[[#chase|chase]]" mode. When the player has eaten a power pill, the ghosts change to "[[#frightened|frightened]]" mode. After being eaten by Pac-Man, the ghosts switch to "[[#respawn|respawn]]" until they have returned to their base.
+Pac-Man uses a very simple [[finite state machine]] to control the behavior of the ghosts. The ghosts have 4 behavior states that they can be in. The ghosts spend most of their time in either "[[#scatter|scatter]]" or "[[#chase|chase]]" mode. When the player has eaten a power pill, the ghosts change to "[[#frightened|frightened]]" mode. After being eaten by Pac-Man, the ghosts switch to "[[#respawn|respawn]]" until they have returned to their base.
 They switch between chase and scatter happens on a fixed timer. The amount of time spent in each mode is different for each level with the bias being towards chase mode as the levels increase. The result of alternating between these two modes is that there is an ebb and flow to the interactions with the ghosts. This was by design as explained by creator, Tōru Iwatani.
@@ Line 43: / Line 43: @@
 <blockquote>“To give the game some tension, I wanted the monsters to surround Pac Man at some stage of the game. But I felt it would be too stressful for a human being like Pac Man to be continually surrounded and hunted down. So I created the monsters’ invasions to come in waves. They’d attack and then they’d retreat. As time went by they would regroup, attack, and disperse again. It seemed more natural than having constant attack.”</blockquote>
-The AI for the Pac-Man ghosts is a collection of very simple rules that they apply depending on which of 4 states they are in. Each of the 4 ghosts has their own ruleset that differs significantly from the others. When used in combination, however, they give the illusion of complex behavior. Because each ghost's behavior is specific to only that ghost, each will be listed separately.
+The AI for the Pac-Man ghosts is a collection of very simple rules that they apply depending on which of 4 states they are in. In some of the states, each of the 4 ghosts has a ruleset that differs significantly from the others. When used in combination, however, they give the illusion of complex behavior.
 ===Chase===
-The normal state for the ghosts is the "chase" behavior. Note that this term is used loosely because not all the ghosts are actually ''"chasing"'' the player. The word "chase" is used more as an identifier of the game state.
+The normal state for the ghosts is the "chase" behavior. Note that this term is used loosely because not all the ghosts are actually ''"chasing"'' the player. The word "chase" is used more as an identifier of the game state. Because each ghost's behavior in the "chase" state is specific to only that ghost, each will be listed separately.
 ====Blinky====

@@ Line 90: / Line 90: @@
 ====Simple Rules Create Complex Environment ====
-The careful construction of simple rules for the 4 ghosts created [emergent behavior] provided myriad gameplay scenarios. While the behaviors of the ghosts seemed complex and almost sentient, there was very little decision-making going on. Novice players felt that there was more AI happening than was actually present. Indeed, the differing rules for the ghosts made for very complex combinations of behaviors.
+The careful construction of simple rules for the 4 ghosts created [[emergent behavior]] provided myriad gameplay scenarios. While the behaviors of the ghosts seemed complex and almost sentient, there was very little decision-making going on. Novice players felt that there was more AI happening than was actually present. Indeed, the differing rules for the ghosts made for very complex combinations of behaviors.
 ====Waves====
@@ Line 106: / Line 106: @@
 ====Appearance of Cooperation====
-Because of the way the individual chase rules were crafted, there seemed to be an [implicit cooperation] between the ghosts. For example, with Blinky always following Pac-Man and Pinky mostly trying to get in front, the player often felt "boxed in". In reality, the only ghost that used the position of another ghost in its calculations was Inky who only indirectly used the location of Blinky to determine its target tile.
+Because of the way the individual chase rules were crafted, there seemed to be an [[implicit cooperation]] between the ghosts. For example, with Blinky always following Pac-Man and Pinky mostly trying to get in front, the player often felt "boxed in". In reality, the only ghost that used the position of another ghost in its calculations was Inky who only indirectly used the location of Blinky to determine its target tile.
 ===What Didn't Work===
 ====Predictability Leads to Exploitation====
-Despite the complex-looking behavior, there was no [randomness] involved in the AI. Even despite the fact that people were often thrown off by the seemingly random behaviors of Inky and Clyde, because the rules were simple, patterns could not only be recognized but they could be pre-determined.
+Despite the complex-looking behavior, there was no [[randomness]] involved in the AI. Even despite the fact that people were often thrown off by the seemingly random behaviors of Inky and Clyde, because the rules were simple, patterns could not only be recognized but they could be pre-determined.
 These patterns were discerned and shared between the gaming community and the game quickly became "broken". The designers thought that by simply increasing the speed of the game as levels progressed, they would prevent players from "beating" the game. This however, was not the case.
@@ Line 119: / Line 119: @@
 ===Lessons Learned===
 (TODO)
 ==Reception by Public==

← Older revision		Revision as of 19:01, 15 July 2011
Line 136:		Line 136:
	* [http://www.mameworld.info/net/pacman/history/p1_01.htm The History of Pac-Man]		* [http://www.mameworld.info/net/pacman/history/p1_01.htm The History of Pac-Man]
	* [http://gameinternals.com/post/2072558330/understanding-pac-man-ghost-behavior Understanding Pac-Man Ghost Behavior]		* [http://gameinternals.com/post/2072558330/understanding-pac-man-ghost-behavior Understanding Pac-Man Ghost Behavior]
		+	* [http://youtu.be/J0H2COjvJPs Video of Pac-Man gameplay]

@@ Line 21: / Line 21: @@
 ==Game Terms==
 There are some general principles about how the game works that need to be understood before one can discuss how the actual decision AI of the ghosts operates.
-====Tiles====
+===Tiles===
 There are some general rules that the ghosts follow when navigating the maze. The game space is broken up into "tiles" that the ghosts use to navigate. This is different than if they were to use a per-pixel location system.
-====Target Tiles====
+===Target Tiles===
 The current navigation of the ghost is based upon a "target tile" which serves as a goal for the ghost to move toward. This system is used regardless of whether the ghosts are in [[#chase|chase]] or [[#scatter|scatter]] modes. Selection of the target tiles is based on the individual ghost logic (below).
-====Intersections====
+===Intersections===
 Navigation decisions are made just before a ghost reaches an intersection. The type of decision that a ghost makes is dependent on which mode it is in. When a ghost is in "[[#frightened|frightened]]" mode, it simply selects a random direction prior to the intersection. In "chase" mode, however, there is more advanced decision processing.
@@ Line 40: / Line 37: @@
 ==Behavior Modes==
-The ghosts have 4 behavior states that they can be in. The ghosts spend most of their time in either "[[#scatter|scatter]]" or "[[#chase|chase]]" mode. When the player has eaten a power pill, the ghosts change to "[[#frightened|frightened]]" mode. After being eaten by Pac-Man, the ghosts switch to "[[#respawn|respawn]]" until they have returned to their base.
+The ghosts have 4 behavior [[Finite State Machine|states]] that they can be in. The ghosts spend most of their time in either "[[#scatter|scatter]]" or "[[#chase|chase]]" mode. When the player has eaten a power pill, the ghosts change to "[[#frightened|frightened]]" mode. After being eaten by Pac-Man, the ghosts switch to "[[#respawn|respawn]]" until they have returned to their base.
 They switch between chase and scatter happens on a fixed timer. The amount of time spent in each mode is different for each level with the bias being towards chase mode as the levels increase. The result of alternating between these two modes is that there is an ebb and flow to the interactions with the ghosts. This was by design as explained by creator, Tōru Iwatani.
 <blockquote>“To give the game some tension, I wanted the monsters to surround Pac Man at some stage of the game. But I felt it would be too stressful for a human being like Pac Man to be continually surrounded and hunted down. So I created the monsters’ invasions to come in waves. They’d attack and then they’d retreat. As time went by they would regroup, attack, and disperse again. It seemed more natural than having constant attack.”</blockquote>
 ===Chase===

@@ Line 20: / Line 20: @@
-==Architectures==
+==Game Terms==
 The AI for the Pac-Man ghosts is a collection of very simple rules. Each of the 4 ghosts has their own ruleset that differs significantly from the others. When used in combination, however, they give the illusion of complex behavior. Because each ghost's behavior is specific to only that ghost, each will be listed separately.
@@ Line 30: / Line 30: @@
 ====Target Tiles====
-The current navigation of the ghost is based upon a "target tile" which serves as a goal for the ghost to move toward. This system is used regardless of whether the ghosts are in [[#chase|chase]] or [[#flee|flee]] modes. Selection of the target tiles is based on the individual ghost logic (below).
+The current navigation of the ghost is based upon a "target tile" which serves as a goal for the ghost to move toward. This system is used regardless of whether the ghosts are in [[#chase|chase]] or [[#scatter|scatter]] modes. Selection of the target tiles is based on the individual ghost logic (below).
 ====Intersections====
-Navigation decisions are made just before a ghost reaches an intersection. Note that there is no decision made at the intersections ''other'' than how to get to the current target tile. Therefore, this phase can adequately be compared to [[steering behaviors]].
+Navigation decisions are made just before a ghost reaches an intersection. The type of decision that a ghost makes is dependent on which mode it is in. When a ghost is in "[[#frightened|frightened]]" mode, it simply selects a random direction prior to the intersection. In "chase" mode, however, there is more advanced decision processing.
 When in the tile prior to the intersection, it looks at all the exit options from that intersection. It then measures the euclidean distance from that tile to the target tile and selects the tile that has the shortest distance. If the ghost is faced with 2 options that are the same distance from the target tile, the tie is broken by preferring directions in the following order: ''up, left, down, right''.
 ===Chase===
@@ Line 64: / Line 73: @@
 ====Clyde====
-The orange ghost is the least aggressive of the ghosts due to his target tile code. There are two parts to Clyde's chase calculations separated by a simple IF statement. If Clyde's location is greater than 8 tiles (Euclidean) away from Pac-Man, he uses the same targeting as Blinky (head directly towards Pac-Man). Once he is within 8 tiles, however, Clyde switches his target tile to his normal patrol corner as per his "[[#Flee|flee]]" behavior. This means that Clyde will never directly encounter the player unless the player makes a poor decision and gets between Clyde and his corner.
+The orange ghost is the least aggressive of the ghosts due to his target tile code. There are two parts to Clyde's chase calculations separated by a simple IF statement. If Clyde's location is greater than 8 tiles (Euclidean) away from Pac-Man, he uses the same targeting as Blinky (head directly towards Pac-Man). Once he is within 8 tiles, however, Clyde switches his target tile to his normal patrol corner as per his "[[#scatter|scatter]]" behavior. This means that Clyde will never directly encounter the player unless the player makes a poor decision and gets between Clyde and his corner.
-===Flee===
+===Scatter===
-When the player eats one of the "power pills", the ghosts change into "flee" mode. When this happens, each ghost's [[#Target Tile|target tile]] is changed to a location outside the maze. These targets are positioned with one outside each corner. The result is that each ghost will go to a different corner and, because they can't actually reach the target tile, will circle in that corner until they go back to chase mode.
+In "scatter" mode, each ghost's [[#Target Tile|target tile]] is changed to a location outside the maze. These targets are positioned with one outside each corner. The result is that each ghost will go to a different corner and, because they can't actually reach the target tile, will circle in that corner until they go back to chase mode.
-Note that the ghosts are not really "fleeing" from the player but merely scattering in 4 different directions. Another result of this is that, as time passes and the ghosts move apart during "flee mode", it is more difficult for the player to reach all 4 of them.
+Note that the ghosts are not really "scattering" ''from the player'' but merely moving in 4 different directions.
 ===Respawn===
@@ Line 80: / Line 92: @@
 ====Simple Rules Create Complex Environment ====
 The careful construction of simple rules for the 4 ghosts created [emergent behavior] provided myriad gameplay scenarios. While the behaviors of the ghosts seemed complex and almost sentient, there was very little decision-making going on. Novice players felt that there was more AI happening than was actually present. Indeed, the differing rules for the ghosts made for very complex combinations of behaviors.
 ====Personality====
@@ Line 114: / Line 129: @@
 {{reflist|sourcename=The Pac-Man Dossier|url=http://home.comcast.net/~jpittman2/pacman/pacmandossier.html|author=Jamey Pittman|venue=web|year=}}
 {{reflist|sourcename=Pinky seek bug|url=http://donhodges.com/pacman_pinky_explanation.htm|author=Don Hodges|venue=web|year=2009}}

@@ Line 17: / Line 17: @@
 ==Description of AI Behavior==
-The ghosts in Pac-Man act as threats requiring the player to avoid them ("[[#chase|chase]]" mode). However, when the player "eats" one of the power pills and, becomes invulnerable for a period of time, the ghosts change roles and must avoid being caught ("[[#flee|flee]]" mode).
+The ghosts in Pac-Man act as threats requiring the player to avoid them ("[[#chase|chase]]" mode). However, when the player "eats" one of the power pills and, becomes invulnerable for a period of time, the ghosts change roles and must avoid being caught ("[[#flee|flee]]" mode). When the ghosts are caught by Pac-Man, their disembodied eyes return to their starting pen where the ghost "respawns".
@@ Line 70: / Line 70: @@
 Note that the ghosts are not really "fleeing" from the player but merely scattering in 4 different directions. Another result of this is that, as time passes and the ghosts move apart during "flee mode", it is more difficult for the player to reach all 4 of them.
 ==Post-Mortem==
@@ Line 76: / Line 79: @@
 ====Simple Rules Create Complex Environment ====
-The careful construction of simple rules for the 4 ghosts provided myriad gameplay scenarios.
+====Personality====
 ===What Didn't Work===
 ====Predictability Leads to Exploitation====
-While the behaviors of the ghosts seemed complex and almost sentient, there was very little decision-making going on. Novice players felt that there was more AI happening than was actually present. Indeed, the differing rules for the ghosts made for very complex combinations of behaviors. However, as these patterns were discerned and shared between the gaming community, the game quickly became "broken". The designers thought that by simply increasing the speed of the game as levels progressed, they would prevent players from "beating" the game. This however, was not the case.
+Despite the complex-looking behavior, there was no [randomness] involved in the AI. Even despite the fact that people were often thrown off by the seemingly random behaviors of Inky and Clyde, because the rules were simple, patterns could not only be recognized but they could be pre-determined.
 Every level beyond the 21st was identical -- both in maze construction and the speed of the ghosts -- therefore, the optimal pattern to "solve" the level was the same. At that point, the game devolved into an endurance test to see how long a player could go before making a mistake.
@@ Line 88: / Line 105: @@
 ===Lessons Learned===
 (TODO)
 ==Reception by Public==
 (TODO)
 ==References==
@@ Line 99: / Line 118: @@
 ==External Links==
-[http://en.wikipedia.org/wiki/Pac-Man Wikipedia:Pac-Man]
+* [http://en.wikipedia.org/wiki/Pac-Man Wikipedia:Pac-Man]
+* [http://www.mameworld.info/net/pacman/history/p1_01.htm The History of Pac-Man]
-[http://www.mameworld.info/net/pacman/history/p1_01.htm The History of Pac-Man]
+* [http://gameinternals.com/post/2072558330/understanding-pac-man-ghost-behavior Understanding Pac-Man Ghost Behavior]
-−
 [http://gameinternals.com/post/2072558330/understanding-pac-man-ghost-behavior Understanding Pac-Man Ghost Behavior]

@@ Line 5: / Line 5: @@
 {{GameInfoBox
 |gametitle=Pac-Man
-|imagefile=http://upload.wikimedia.org/wikipedia/en/5/59/Pac-man.png
+|imagefile=Pac-man.png
 |developer=Namco
 |publisher=Namco, Midway
@@ Line 90: / Line 90: @@
 ==Reception by Public==
+(TODO)
 ==References==