Chapter 2: Gameplay Details
"As
Pac-Man was originally conceived to appeal to women players, it is
a very easy and approachable game. I believe that is an ingredient
in the longevity of the game."-Toru Iwatani, creator
of Pac-Man
The
Basics
The
premise of Pac-Man is delightfully simple: using a four-way
joystick, the player guides Pac-Man-up, down, left, and
right-through a maze filled with dots for him to gobble up.
Four ghost monsters are also in the maze and chase after our hero,
trying to capture and kill him.
The goal is to clear the maze of
dots while avoiding the deadly ghosts. Each round starts with the
ghosts in the "monster pen" at the center of the maze,
emerging from it to join in the chase.
If Pac-Man is captured by a
ghost, a life is lost, the ghosts are returned to their pen, and a
new Pac-Man is placed at the starting position before play
continues. When the maze is cleared of all dots, the board is
reset, and a new round begins. If Pac-Man gets caught by a ghost
when he has no extra lives, the game is over.
There are 244 dots
in the maze, and Pac-Man must eat them all in order to proceed to
the next round. The 240 small dots are worth ten points each, and
the four large, flashing dots - best known as energizers - are
worth 50 points each.
This yields a total of 2,600 points for
clearing the maze of dots each round. Players have two ways to
increase their score beyond what is earned from eating dots:
The first way to
increase your score each round is by turning the tables on your
enemies by making them your prey. Whenever Pac-Man eats one of the
four energizer dots located in the corners of the maze, the ghosts
reverse their direction and, in early levels, turn the same shade
of blue for a short period of time before returning to normal.
While blue, they are vulnerable to Pac-Man and can be gobbled up
for extra points providing they are caught before the time
expires. After being eaten, a ghost's eyes will return to the
monster pen where it is resurrected, exiting to chase Pac-Man once
again.
The first ghost captured after an energizer has been eaten
is always worth 200 points. Each additional ghost captured from
the same energizer will then be worth twice as many points as the
one before it-400, 800, and 1,600 points, respectively. If
all four ghosts are captured at all four energizers, an additional
12,000 points can be earned on these earlier levels. This should
not prove too terribly difficult to achieve for the first few
rounds as the ghosts initially remain blue for several seconds.
Soon after, however, the ghosts' "blue time" will get
reduced to one or two seconds at the most, making it much more
problematic to capture all four before time runs out on these
boards. By level 19, the ghosts stop turning blue altogether and
can no longer be eaten for additional points.
The second way to
increase your score each round is by eating the bonus
symbols (commonly
known as fruit)
that appear directly below the monster pen twice each round for
additional points. The first bonus fruit appears after 70 dots
have been cleared from the maze; the second one appears after 170
dots are cleared.
Each fruit is worth anywhere from 100 to 5,000
points, depending on what level the player is currently on.
Whenever a fruit appears, the amount of time it stays on the
screen before disappearing is always between nine and ten seconds.
The exact
duration (i.e., 9.3333 seconds,
10.0 seconds, 9.75 seconds, etc.) is variable and does
not become predictable with
the use of patterns. In other words, executing the same
pattern on the same
level twice is no guarantee for
how long the bonus fruit will stay onscreen each time.
This
usually goes unnoticed given that the majority of patterns are
designed to eat the bonus fruit as quickly as possible after it
has been triggered to appear. The symbols used for the last six
rounds completed, plus the current round are also shown along the
bottom edge of the screen (often called the fruit counter or level
counter). See Table
A.1 in the
appendices for all bonus fruit and scoring values, per level.
Ghosts have three
mutually-exclusive modes of behavior they can be in during play:
chase, scatter, and frightened. Each mode has
a different objective/goal to be carried out:
-
CHASE - A
ghost's objective in chase mode is to find and capture
Pac-Man by hunting him down through the maze. Each ghost exhibits
unique behavior when chasing Pac-Man, giving them their different
personalities: Blinky (red) is very aggressive and hard to shake
once he gets behind you, Pinky (pink) tends to get in front of
you and cut you off, Inky (light blue) is the least predictable
of the bunch, and Clyde (orange) seems to do his own thing and
stay out of the way.
-
SCATTER - In
scatter mode, the ghosts give up the chase for a few
seconds and head for their respective home corners. It is a
welcome but brief rest-soon enough, they will revert to
chase mode and be after Pac-Man again.
-
FRIGHTENED - Ghosts
enter frightened mode whenever Pac-Man eats one of the
four energizers located in the far corners of the maze. During
the early levels, the ghosts will all turn dark blue (meaning
they are vulnerable) and aimlessly wander the maze for a few
seconds. They will flash moments before returning to their
previous mode of behavior.
Reversal
Of Fortune
In
all three modes of behavior, the ghosts are prohibited from
reversing their direction of travel. As such, they can only choose
between continuing on their current course or turning off to one
side or the other at the next intersection. Thus, once a ghost
chooses which way to go at a maze intersection, it has no option
but to continue forward on that path until the next intersection
is reached.
Of course, if you've spent any time playing Pac-Man,
you already know the ghosts will reverse direction at
certain times. But how can this be if they are expressly
prohibited from doing so on their own? The answer is: when
changing modes, the system can override the ghosts' normal
behavior, forcing them to go the opposite way. Whenever this
happens, it is a visual indicator of their behavior changing from
one mode to another.
Ghosts are forced to reverse direction by the
system anytime the mode changes from: chase-to-scatter,
chase-to-frightened, scatter-to-chase, and scatter-to-frightened.
Ghosts do not reverse direction when changing back from frightened
to chase or scatter modes.
When the system
forces the ghosts to reverse course, they do not necessarily
change direction simultaneously; some ghosts may continue forward
for a fraction of a second before turning around.
The delay
between when the system signals a reversal and when a ghost
actually responds depends on how long it takes the ghost to enter
the next game tile along its present course after the reversal
signal is given (more on tiles in Chapter 3). Once the ghost
enters a new tile, it will obey the reversal signal and turn
around.
Scatter,
Chase, Repeat...
Ghosts alternate
between scatter and chase modes during gameplay at predetermined
intervals. These mode changes are easy to spot as the ghosts
simultaneously reverse direction when they occur. Scatter modes
happen four times per level before the ghosts stay in chase mode
indefinitely.
Good players will take full advantage of the scatter
periods by using the brief moment when the ghosts are not chasing
Pac-Man to clear dots from the more dangerous areas of the maze.
The scatter/chase timer gets reset whenever a life is lost or a
level is completed. At the start of a level or after losing a
life, ghosts emerge from the ghost pen already in the first of the
four scatter modes.
For
the first four levels, the first two scatter periods last for
seven seconds each. They change to five seconds each for level
five and beyond. The third scatter mode is always set to five
seconds. The fourth scatter period lasts for five seconds on level
one, but then is only 1/60th of a second for the rest
of play. When this occurs, it appears as a simple reversal of
direction by the ghosts.
The first and second chase periods last
for 20 seconds each. The third chase period is 20 seconds on level
one but then balloons to 1,033 seconds for levels two through
four, and 1,037 seconds for all levels beyond-lasting over
17 minutes! If the ghosts enter frightened mode, the scatter/chase
timer is paused.
When time runs out, they return to the mode they
were in before being frightened and the scatter/chase timer
resumes. This information is summarized in the following table
(all values are in seconds):
Mode
|
Level
1
|
Levels
2-4
|
Levels
5+
|
Scatter
|
7
|
7
|
5
|
Chase
|
20
|
20
|
20
|
Scatter
|
7
|
7
|
5
|
Chase
|
20
|
20
|
20
|
Scatter
|
5
|
5
|
5
|
Chase
|
20
|
1033
|
1037
|
Scatter
|
5
|
1/60
|
1/60
|
Chase
|
indefinite
|
indefinite
|
indefinite
|
Frightening
Behavior
Anytime Pac-Man
eats one of the four energizers on the level, the ghosts reverse
direction and, on earlier levels, go into frightened
mode. Frightened ghosts turn dark
blue and wander about the maze for a few moments, flashing briefly
as a warning before returning to normal. Ghosts use a
pseudo-random number generator (PRNG) to pick a way to turn at
each intersection when frightened.
The PRNG generates an
pseudo-random memory address to read the last few bits from. These
bits are translated into the direction a frightened ghost must
first try. If a wall blocks the chosen direction, the ghost then
attempts the remaining directions in this order: up,
left, down, and right,
until a passable direction is
found. The PRNG gets reset with an identical seed value every new
level and every new life, causing predictable results.
This is why
the frightened ghosts' movements are repeatable in the context of
a memorized pattern or sequence. As the levels progress, the time
ghosts spend in frightened mode grows shorter until eventually
they no longer turn blue at all (they still reverse direction).
Refer to Table
A.1 in the
appendices for the frightened time in seconds and number of
flashes, per level.
Speed
The game starts
with Pac-Man at 80% of his maximum speed. By the fifth level,
Pac-Man is moving at full speed and will continue to do so until
the 21st
level. At that point, he slows
back down to 90% and holds this speed for the remainder of the
game. Every time Pac-Man eats a regular dot, he stops moving for
one frame (1/60th
of a second), slowing his
progress by roughly ten percent-just enough for a following
ghost to overtake him.
Eating an energizer dot causes Pac-Man to
stop moving for three frames. The normal speed maintained by the
ghosts is a little slower than Pac-Man's until the 21st
level when they start moving
faster than he does. If a ghost enters a side tunnel, however, its
speed is cut nearly in half.
When frightened, ghosts move at a
much slower rate of speed than normal and, for levels one through
four, Pac-Man also speeds up. The table below summarizes the speed
data for both Pac-Man and the ghosts, per level. This information
is also contained in Table
A.1 in the
appendices.
|
PAC-MAN
SPEED
|
GHOST
SPEED
|
LEVEL
|
NORM
|
NORM
DOTS
|
FRIGHT
|
FRIGHT
DOTS
|
NORM
|
FRIGHT
|
TUNNEL
|
1
|
80%
|
71%
|
90%
|
79%
|
75%
|
50%
|
40%
|
2
- 4
|
90%
|
79%
|
95%
|
83%
|
85%
|
55%
|
45%
|
5
- 20
|
100%
|
87%
|
100%
|
87%
|
95%
|
60%
|
50%
|
21+
|
90%
|
79%
|
-
|
-
|
95%
|
-
|
50%
|