Foundation game design with ActionScript 3.0

677 Pages·2012·30.171 MB·English

by  Spuy, Rex van der

Foundation Game Design
with ActionScript 3.0

Second Edition

Rex van der Spuy
Foundation Game Design with ActionScript 3.0, Second Edition
Copyright © 2012 by Rex van der Spuy
All rights reserved. No part of this work may be reproduced or transmitted in any form or by any means, electronic or
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ISBN-13 (pbk): 978-1-4302-3993-2
ISBN-13 (electronic): 978-1-4302-3994-9
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Credits
President and Publisher: Copy Editor:
Paul Manning Mary Behr
Lead Editor: Compositor:
Ben Renow-Clarke Apress (Brigid Duffy)
Technical Reviewers: Production Editor:
Joshua Freeney Brigid Duffy
Editorial Board: Indexer:
Steve Anglin, Mark Beckner, Ewan Buckingham, Gary BIM Indexing & Proofreading Services
Cornell, Morgan Ertel, Jonathan Gennick, Jonathan
Hassell, Robert Hutchinson, Michelle Lowman, James Artist:
Markham, Matthew Moodie, Jeff Olson, Jeffrey Pepper, SPi Global
Douglas Pundick, Ben Renow-Clarke, Dominic
Cover Image Artist:
Shakeshaft, Gwenan Spearing, Matt Wade, Tom
Corné van Dooren
Welsh
Cover Designer:
Coordinating Editor:
Anna Ishchenko
Kelly Moritz
Dedicated to my father, Mani van der Spuy,
without whom this book would not have been written.
Thanks, Dad, for always believing in me.
CONTENTS AT A GLANCE

Contents
_________________________________________________________________________________

About the Author………………………………………………………………...xiii
About the Technical Reviewer………………………………………………...xiv
About the Cover Image Designer……………………………………………..xv
Acknowledgements…………………………………………………………….xvi
Introduction…………………………………………………………………..…xvii
Chapter 1: Programming Foundations: How To Make A Video Game……… ..1
Basic requirements .............................................................................................................. 2
1. A computer .................................................................................................................... 2
2. Graphic design software ............................................................................................... 2
3. Computer programming software ................................................................................. 3
Adobe Flash Professional ................................................................................................. 5
Things you need to know ..................................................................................................... 5
And the things you don’t need to know ................................................................................ 6
It’s all about programming .................................................................................................... 6
Programming? But I’m terrible at math! ............................................................................... 7
I already know how to program! ........................................................................................... 8
iv
What kind of games can I make? ..................................................................................... 8
Learning new terms .......................................................................................................... 9
Laying the foundation ....................................................................................................... 9
Using Flash Builder ............................................................................................................ 10
Setting up the work environment in Flash Builder .......................................................... 10
Writing your first program ................................................................................................... 20
ActionScript files and the .as file extension ....................................................................... 20
I’ll take that to go! ............................................................................................................... 22
A little magic with sprites ................................................................................................ 23
Don’t skip class! .............................................................................................................. 25
Using the constructor method ......................................................................................... 27
Aligning code .................................................................................................................. 29
What’s your directive? ........................................................................................................ 32
Adding comments to your code ......................................................................................... 34
Running your program and compiling the SWF file ........................................................... 36
What happened when you compiled the program .......................................................... 38
It didn’t work? ..................................................................................................................... 40
Some common error messages ...................................................................................... 43
Confirm your program with the original source files ....................................................... 45
More about Flash Builder ................................................................................................... 45
Editing window quirks and features ................................................................................ 45
Perspectives ................................................................................................................... 48
A little more about AS3.0 and the Flash Player ................................................................. 52
Naming conventions........................................................................................................... 54
Summary ............................................................................................................................ 55
Chapter 2: Making Game Graphics ..................................................................... 57
Create a game world background ...................................................................................... 59
Create a new file in Photoshop ....................................................................................... 60
Draw the sky ................................................................................................................... 64
Drawing hills .................................................................................................................... 76
Drawing with the pen tool ............................................................................................... 79
v
Duplicating, modifying, and arranging layers .................................................................. 91
Bevel and emboss .......................................................................................................... 96
Making boxes with the rectangular selection tool ......................................................... 100
Making a game character ................................................................................................ 106
Create a new file ........................................................................................................... 106
Draw your character ..................................................................................................... 107
Making buttons ................................................................................................................. 110
Create a new file ........................................................................................................... 111
Draw the button............................................................................................................. 111
Using the type tool ........................................................................................................ 114
Making more buttons .................................................................................................... 115
Save your work and make the PNG files ...................................................................... 117
Checking your work.......................................................................................................... 118
More about Photoshop ..................................................................................................... 119
Summary .......................................................................................................................... 120
Chapter 3: Programming Objects ...................................................................... 121
But I’m a bit scared of programming! ............................................................................... 122
Loading and displaying images ........................................................................................ 123
Setting up a new AS3.0 project .................................................................................... 124
Understanding the setup file ......................................................................................... 126
Set up the Flash Player with a metadata tag ................................................................ 127
Loading and displaying the background.png image ..................................................... 130
How did that work? ....................................................................................................... 132
Variables ....................................................................................................................... 134
Variable types ............................................................................................................... 135
Creating empty boxes ................................................................................................... 136
Creating instances and objects..................................................................................... 137
Displaying the image on the stage ............................................................................... 140
Understanding the code structure................................................................................. 147
Positioning Sprites on the stage ................................................................................... 148
Programming buttons ....................................................................................................... 158
vi
Understanding dot notation ........................................................................................... 159
Methods ........................................................................................................................ 159
Using method calls ....................................................................................................... 160
Using function definitions .............................................................................................. 161
Using a basic method ................................................................................................... 163
Understanding events and event listeners ................................................................... 168
Making your buttons work ............................................................................................. 177
Controlling Sprite objects with properties......................................................................... 178
Going up and down ....................................................................................................... 180
Moving incrementally ....................................................................................................... 182
Tracing the output ......................................................................................................... 183
Using increment and decrement operators .................................................................. 184
Limiting movement ........................................................................................................ 185
Making it bigger and smaller ......................................................................................... 189
Vanishing! ..................................................................................................................... 192
Spinning around ............................................................................................................ 195
More properties? ........................................................................................................... 198
Centering Sprites ............................................................................................................. 198
Code summary ................................................................................................................. 202
Summary ....................................................................................................................... 206
Chapter 4: Decision Making ............................................................................... 209
Using text ......................................................................................................................... 210
Setting up the project .................................................................................................... 210
The classes you have to import .................................................................................... 212
Creating TextFormat and TextField objects ................................................................. 213
Setting the format of text ............................................................................................... 214
Configuring and displaying the output text ................................................................... 216
Configuring and displaying the input field ..................................................................... 218
Building a simple guessing game .................................................................................... 222
Understanding the program structure ........................................................................... 222
Learning more about variables ........................................................................................ 224
vii
Listening for key presses .............................................................................................. 227
Making decisions .............................................................................................................. 231
Displaying the game status ........................................................................................... 238
Using postfix operators to change variable values by one .............................................. 240
Tying up strings............................................................................................................. 241
Hey, why use the gameStatus variable, anyway? ........................................................ 245
Using uint vs. int variables ............................................................................................ 245
Winning and losing ....................................................................................................... 246
Modular programming with methods ............................................................................ 252
Polishing up ...................................................................................................................... 253
Tackling random numbers ............................................................................................ 254
Disabling the Enter key ................................................................................................. 258
Making really nice buttons ............................................................................................... 260
Understanding the concepts ......................................................................................... 262
Loading the images and displaying the button ............................................................. 263
Understanding the mouse events ................................................................................. 265
Adding the button to the number guessing game ............................................................ 271
Disabling the button at the end of the game ................................................................. 272
Managing complex code ............................................................................................... 278
Project extensions ............................................................................................................ 279
Make a Play again button ............................................................................................. 279
Tracking guesses .......................................................................................................... 280
Adding a visual display ................................................................................................. 281
Turning the tables ......................................................................................................... 281
A quick guide to embedding fonts .................................................................................... 281
Summary .......................................................................................................................... 284
Chapter 5: Controlling A Player Character ....................................................... 285
Controlling a player character with the keyboard ............................................................. 285
Controlling with the keyboard—the wrong way! ........................................................... 286
Controlling the keyboard—the right way! ...................................................................... 290
Moving with velocity ...................................................................................................... 292
viii
Using the new keyDownHandler ................................................................................... 294
Using the keyUpHandler ............................................................................................... 294
Using the enterFrameHandler ...................................................................................... 296
Setting stage boundaries .............................................................................................. 298
Blocking movement at the stage edges ........................................................................ 298
Screen wrapping ........................................................................................................... 303
Embedding images .......................................................................................................... 304
Scrolling ........................................................................................................................... 307
Looking at the code ...................................................................................................... 310
Better scrolling .............................................................................................................. 313
Even better scrolling ..................................................................................................... 320
Taking it further ................................................................................................................ 323
Parallax scrolling ........................................................................................................... 324
Summary .......................................................................................................................... 329
Chapter 6: Bumping Into Things ....................................................................... 331
Basic collision detection with hitTestObject .................................................................. 331
Using hitTestObject ...................................................................................................... 335
Triggering a change of state ............................................................................................ 337
Reducing a health meter ............................................................................................... 341
Using scaleX to scale the meter based on a percentage ............................................. 343
Updating a score ........................................................................................................... 344
Picking up and dropping objects ................................................................................... 351
The bad news about hitTestObject .................................................................................. 357
Detecting collisions with the bounding box ................................................................... 358
Learning to live with it ................................................................................................... 359
Creating subobjects ...................................................................................................... 360
Advanced collision detection strategies ........................................................................ 364
Working with vector based collision detection ................................................................. 365
Preventing objects from overlapping ............................................................................ 365
Programming with the Collision class ........................................................................... 373
Another look at methods, arguments, and parameters ................................................. 378
ix