Game Development Reference
In-Depth Information
rate independent of the
.swf
file's frame rate (FPS). The
.swf
file can have a frame rate setting of
25 (for example), but the game can run at a 30 frame ticks a second. To do this, we first set the
frameRate
to the desired number of frame update ticks we want per second (30). When
Main.as
calls the
startTimer
function (described in detail when we get to the section on the
init
function), the
gameTimer
is put into action. First, we will calculate the
timerPeriod
value as
1000 /
frameRate
. With the
updateAfterEvent
function call (in the
runGame
function), we help to smooth
out the render of the screen by asking the Flash display engine to update at the rate of the
Timer
,
not the frame rate set in the
.swf
. So, going back to our example, if the game SWF is set to run at
25 FPS, and the
frameRate
is set to 30 ticks, the
updateAfterEvent
will help to smooth out the
rendering of the screen by asking the Flash display engine to update at the timer tick rate (30),
not the
.swf
file's FPS setting (25).
The
timerPeriod
will be passed into the
Timer
instance and the game will attempt to run at this
rate. We say “attempt” because if the game includes too many on screen moving objects or more
logic than can be computed inside the
timerPeriod
number of milliseconds (or a combination of
both), then there will be a noticable slowdown in the game screen updates. In later chapters, we
will add functionality to the
runGame
function to mitigate some of these issues.
The screen definition variables
The screen definition variables create instances of our
BasicScreen
class. This is a rather simple
class that allows a single positional text box and an OK button on the screen. We will use this
simple screen for the title, instructions, level, and game over screens. We will customize each
screen when we create the
init
function override in our game's
Main.as
class. Note that the
levelInText
is a special variable. Setting this string to a default value will allow the
leveInScreen
to display some default text along on each new level. This text can be combined with dynamic
text to create a screen that says something like Level 1 with the word “Level” being the default text
and the number “1” being the dynamic text.
public var titleScreen:BasicScreen;
public var gameOverScreen:BasicScreen;
public var instructionsScreen:BasicScreen;
public var levelInScreen:BasicScreen;
public var levelInText:String;
public var screenTextFormat:TextFormat;
public var screenButtonFormat:TextFormat;
We also create two
TextFormat
objects that will be used for defining the format of the text on the
screens and the format of the button text.
The ScoreBoard variables
The
scoreBoard
instance of the
ScoreBoard
class will handle a simple heads up display (HUD) for
the user with information such as the current score. It is a simple framework class that will be
customized in the
init
function override in each game's
Main.as
class. The changes will depend
on the game that is to be created. We also define a
TextFormatObject
for the basic look of the
text for our scoreboard text:
scoreBoardTextFormat
.
The Game object variable
The
Game
object, represented by the variable simply named
game
, is an instance of the
Game
class.
The
Main.as
class's
init
function override will inistantiate this. For example, the
StubGame.as
we
