Computer Game Design 101

2 ActionScript is… Object-oriented programming Everything you do in ActionScript does something to some object* Some objects are called Symbols in Flash –Movie Clip –Graphic –Button * anything you can manipulate in some way

3 Object oriented? You can decide what happens when a user clicks a button without worrying about how the button (or program) knows that it has been clicked You can decide what changes to make to an object’s properties without knowing the internal mechanics of how those changes were made You can program tasks incrementally without sitting down and writing the whole program from start to finish in one session

4 ActionScript Deconstructed Class: a group of items that are similar in some way –Items are called objects or instances of the class Objects can be concrete (like a button or graphic) or abstract (like a variable that is invisible, but hold data) Objects have two aspects form (properties) and function (methods) Each property and method is defined by Actions (pieces of code that tell Flash how to manipulate a target object at any point in your movie).

5 ActionScript Metaphor Ball could be considered a class of items defined as “spherical things” –One object in this class is a movie clip called Tennis_ball The properties of Tennis_ball might be the color neon green or a 20-pixel diameter Its methods might be bounce, roll, and/or spin –A 2 nd object in the ball class might be Softball Properties white…etc.

6 ActionScript Flow Flash executes ActionScript statements starting with the first statement and continuing in order until it reaches the final statement or a statement that instructs ActionScript to go somewhere else.

7 One type of action that sends ActionScript somewhere other than the next statement is an if statement

8 Actions Tell Flash to do something –Frame actions –Object actions Actions also can have parameters

9 gotoAndPlay This frame action sends the playhead to the specified frame in a scene and plays from that frame. If no scene is specified, the playhead goes to the specified frame in the current scene.

10 Functions Perform a specific task Like in a spreadsheet program (Excel)

11 getVersion Returns the Flash Player version number and operating system information. You can use this function to determine whether the Flash Player that is in use can handle your Actionscript.

12 Properties All available information about an object You can use ActionScript to read and modify object properties All property names begin with an underscore (e.g., _visible)

13 _visible = false This property make an object invisible Assign the following action to a button… On (release) { _visible = false; } Button disappears on mouse click

14 Method Similar to actions in that they effect objects Built into objects Invoked (Executed) through dot notation

15 RocketMC.gotoAndPlay(“BlastOff”); ActionScript notation must end in ; Movie clip Rocket MC goes to a frame labeled BlastOff and plays

16 Variables hold data for use in your Flash movies Variables can hold any type of data You could store: –User name –Result of calculation –True or false value

17 Expressions An expression is any statement that Flash can evaluate and that returns a value. You can create an expression by combining operators and values or by calling a function.

18 Operators Expressions use operators to tell Flash how to manipulate the values in the expression. They are the commands that say “add these values” or “multiply these numbers”

19 Some types of operators Assignment: are used to assign values to variables. The most common is (=). It makes the variable on the left equal to the value of the variable or expression on the right. Comparison and equivalence: ( ), (< =) Numeric: perform mathematical operations on values

20 Looping When you need to repeat certain actions in your movies more than once. Makes coding more efficient, using the same set of commands as many times as necessary to complete a task.

21 Looping examples while Creates a loop that continues to repeat as long as a condition remains true for Creates a loop that executes a specific number of times using a counter for…in Creates a loop that executes once for each member of a group of objects (class) This makes certain that the entire group of objects is processed in the same way

22 Hints Before you begin writing scripts, formulate your goal and understand what you want to achieve. Planning your scripts is as important as developing storyboards for your work. Start by writing out what you want to happen in the movie, as in this example: –I want to create my whole site using Flash. –Site visitors will be asked for their name, which will be reused in messages throughout the site. –The site will have a draggable navigation bar with buttons that link to each section of the site. –When a navigation button is clicked, the new section will fade in at the center of the Stage. –One scene will have a contact form with the user's name already filled in.