Game Design

1
Game Design

• CSE 203 Lecture 6
• Annatala Wolf

2
Constructors

• If you use classes in your design, you may want
  to use constructors. A constructor is an
  operation that automatically runs when an object
  is created.
• To call a constructor, you use the phrase New
  Type(args go here)
• You can think of the constructor as a function
  that returns a Type object.

3
Constructor Example

• Class Dude
• Private Define name As Text
• Constructor(name As Text)
• This.name name
• End Constructor
• End Class
• Method Main()
• // Make a Dude object and set its name
• Define fred As Dude New Dude(Fred)
• End Method

4
Default Constructor

• In Phrogram, all classes have a default (empty)
  constructor, even if you dont define one. If
  you dont call a constructor, it will call the
  default one for you when you make the object.
• // Calls default Constructor()
• // for Sprite class!
• Define jumper As Sprite

5
New Objects

• Every time you call a constructor, you get a new
  object. So this resets the objectyoull lose
  anything you did with it before.
• // Calls Foos Constructor()
• Define blather As Foo
• // Overwrites blather
• blather New Foo(stuff, 12)
• // Overwrites blather again
• blather New Foo()

6
Dont Get Lost!

• If you have difficulty getting classes to
  workremember, you dont need to use them for
  your project.
• You should, however, understand how to separate
  your code into operations. Your Main() method
  should be relatively clean and short, and most of
  the variables you use should be at the program
  level.

7
Kinds of Projects

• Your project will probably be a game of some
  sort. This is partly because Phrogram lends
  itself well to game programming.
• Non-game projects are also possible. You could
  write a simulation, a tool, or an application.
  But it should be tricky to implement, and
  interesting!

8
Game Genres

• Strategy puzzle games, strategic combat
• Action side-scroller, platformer, first-person
  shooter, puzzle (Tetris), fighting
• Roleplay/RPG usually with epic plot, multiple
  characters, character growth
• Adventure mix of action and RPG
• Sports sports, card games, driving
• Simulation usually resource management

9
Planning the Game

• Game design begins with a concept. What do you
  want the game to be like for the player?
• Generally, there will be a set of different
  situations a player can be presented with.
• There may be multiple levels to complete
• There might be menu windows that pop up
• There could be different modes of play
• There might be choices before the game starts

10
Game State

• With all these different things going on, how can
  you keep track of what the program is supposed to
  do?
• The idea of game state encompasses not only the
  data the game has access to and where the code is
  running, but also what mode the game is in.
• We can use variables to remember what state the
  game is in.

11
Constants

• Sometimes, youll want to use a variable to refer
  to the same value over and over again, without
  ever changing. This kind of variable is called a
  constant.
• Constants are useful for remembering constant
  values (like PI 3.14159), or state labels
  (NORTH 1, EAST 2, etc.)

12
Defining Constants

• To define constants, use the keyword Constant
  (instead of Define). You need to assign them
  when you create them.
• Constant PI As Decimal 3.1416
• Constant MAIN_MENU As Integer 2
• Note that constant values are traditionally
  written in ALL_CAPS.

13
Using Constants

• Constants are used just like variables, but they
  cant be reassigned. (You can even make them
  private class members if you want to use them
  only in that class.)
• area PI radius radius
• MAIN_MENU 3 // error! constant

14
Back To State

• Consider a game that starts with a character
  creation screen, then toggles between a map
  screen and a combat screen. How would we keep
  track of it?
• At the program level, well make
• Constant GS_CREATE As Integer 1
• Constant GS_MAP As Integer 2
• Constant GS_COMBAT As Integer 3

15
Testing For State

• We can segregate each mode of the game into a
  separate operation, for simplicity. Well call
  these from the main event loop.
• While (Not gameOver)
• If (gameState GS_CREATE) Then
• charCreation()
• Else If (gameState GS_MAP) Then
• mapScreen()
• Else If (gameState GS_COMBAT) Then
• combatScreen()
• End If
• Delay(refreshRate)
• RefreshScreen()
• End While

16
Aiming For The Moon

• Part of the project proposal process is deciding
  how much you want to tackle.
• Games will be graded on originality, fun, and
  difficulty. But some things are too difficult to
  complete in four weeks.
• Solution aim for something hard, that you can
  scale back if necessary. ?