Thomson Course Technology PTR and the author have attempted through-out this book to distinguish proprietary trademarks from descriptive terms by following the capitalization style used
Trang 2Game Programming
for Teens, Second Edition
Maneesh Sethi
Trang 3Publisher and General Manager, Thomson Course Technology PTR:
© 2005 by Thomson Course Technology PTR All rights reserved No part
of this book may be reproduced or transmitted in any form or by any
means, electronic or mechanical, including photocopying, recording, or
by any information storage or retrieval system without written
permis-sion from Thomson Course Technology PTR, except for the inclupermis-sion of
brief quotations in a review.
The Premier Press and Thomson Course Technology PTR logo and
related trade dress are trademarks of Thomson Course Technology and
may not be used without written permission.
BlitzPlus, Blitz3D, BlitzBasic2D, and BlitzMax are trademarks of Blitz
Research, Ltd Paint Shop Pro is a registered trademark of Corel
Corpora-tion MilkShape 3D is a registered trademark of ChumbaLum sOft.
CoolEdit Pro is a registered trademark of Syntrillium Software Corporation.
All other trademarks are the property of their respective owners.
Important: Thomson Course Technology PTR cannot provide software
support Please contact the appropriate software manufacturer’s
techni-cal support line or Web site for assistance.
Thomson Course Technology PTR and the author have attempted
through-out this book to distinguish proprietary trademarks from descriptive terms
by following the capitalization style used by the manufacturer.
Information contained in this book has been obtained by Thomson
Course Technology PTR from sources believed to be reliable However,
because of the possibility of human or mechanical error by our sources,
Thomson Course Technology PTR, or others, the Publisher does not
guarantee the accuracy, adequacy, or completeness of any information
and is not responsible for any errors or omissions or the results obtained
from use of such information Readers should be particularly aware of
the fact that the Internet is an ever-changing entity Some facts may have
changed since this book went to press.
Educational facilities, companies, and organizations interested in
multi-ple copies or licensing of this book should contact the publisher for
quantity discount information Training manuals, CD-ROMs, and
por-tions of this book are also available individually or can be tailored for
Thomson Course Technology PTR,
a division of Thomson Course Technology
25 Thomson Place Boston, MA 02210 http://www.courseptr.com
Trang 4For my parents, Neelam and Prabhjot
Trang 5Jeez, there are so many people to thank This feels like I’m accepting an Oscar™: I’m
afraid the band will start playing and usher me off the stage Anyway, first of all thankyou André LaMothe for giving me a chance and taking me out to lunch I will get youback for that one day Thank you everyone at Premier Press: my production editor JennyDavidson, my copy editor, Kezia Endsley, my acquisitions editor, Emi Smith, and my CDeditor, Brandon Penticuff
Thanks go out to Adam Hepworth, who spent a lot of his “busy” day helping read my textand correcting a lot of errors To all of my brothers and sisters, Rachi, who offered her helpeven though she was across an ocean, Nagina, whose love and support (and numerousphone calls) helped carry me through, and Ramit, who gave me a person to look up to andwho helped me through the thick and thin (as well as giving me the chance to use
“abeyance” in a sentence) Thanks for being here and giving me support when I needed it
To my mom and dad: I couldn’t have done this without you I love you so much
Finally, thanks to Edgar L Ibarra (Feo) for his artwork and Thomas Stenbäck for his work
on the CD’s music Also, to Ari Feldman, for allowing me to use his sprite library on theCD
Also, for contributing a demo program to the book, thanks to Jason Brasier and Edgar
Ibarra for Rockfall and Marcus “Eikon” Smith for Galaxiga.
And to everyone whose name I forgot, you know who you are Thanks!
IV
Acknowledgments
Trang 6M ANEESH S ETHI is a high school student in California who will be enrolled at Stanford
University in 2006 Maneesh has worked with Web design and development since he was
in fifth grade and was the founder and head designer of Standard Design, a Web site
design company Maneesh has taught game programming on TechTV’s Call for Help and
at game programming conferences such as the XGDX He is the author of Game
Programming for Teens (First Edition) and Web Design for Teens, both published by Course
PTR, and How to Succeed as a Lazy Student.
Besides game programming, Maneesh enjoys playing games (of course), sports such as
tennis and basketball, and of course, sleep Learn more about Maneesh, as well as his
award-winning T-shirts and iPod sock case at www.maneeshsethi.com
V
About the Author
Trang 7Contents
Introduction xi
Part I: The Basics of BASIC 1
Chapter 1 Getting Started 3
A Brief History of BASIC .3
Installing BlitzPlus .4
Windows and Panels .5
Toolbars .6
Menus .7
The First Game: KONG .7
Compiling the Code 16
Summary .18
Chapter 2 Getting to Know BASIC 19
Hello, World! .19
Variables 23
Declaring Variables .23
Using Variables .24
Input 26
Conditionals .28
Truth and Falsehood .28
If Then .29
Trang 8Contents VII
If Then…Else .30
Select…Case 32
Logical Operators .33
The NOT Operator .35
The Goto Command .35
A Text-Based Guessing Game .37
Summary .39
Chapter 3 Loops, Functions, Arrays, and Types 41
Understanding Loops .41
For…Next 42
While…Wend 46
Repeat…Until .48
Understanding Functions .51
Scope Considerations 53
When to Use Functions .57
Understanding Arrays .58
Multi-Dimensional Arrays .64
Using Types 67
Coordinate Systems .75
For…Each…Next .77
Putting It All Together: Textanoid! .79
Summary .93
Chapter 4 The Style Factor 95
Developing Style .95
White Space and Indentation .96
Comments .97
Pre-Program Comments 99
Main Program Comments .100
Function Comments .100
Function and Variable Names .101
Names .101
Naming Format .101
Summary .103
Trang 9VIII
Part II: Getting Graphical 105
Chapter 5 Beginning Graphics 107
Creating the Graphics Window .107
Width and Height .108
Color Depth .109
[Mode] .110
Images .114
LoadImage .114
DrawImage .116
CreateImage 118
MaskImage 122
Colors .125
RGB .126
Color .128
Cls and ClsColor .130
Summary 131
Chapter 6 Page Flipping and Pixel Plotting 133
Page Flipping .133
Buffers .136
SetBuffer .137
CreateImage 143
Locking and Unlocking Buffers .156
Lock/Unlock .156
ReadPixel()/ReadPixelFast() .157
WritePixel/WritePixelFast .161
Using Buffers: A Paint Program .166
Initialization 168
Main Loop 170
Functions .172
Summary 180
Trang 10Contents IX
Chapter 7 Basic Image Programming 181
Transformations .181
Translating .181
Scaling .186
Rotation .209
Parallaxing .217
TileBlock and TileImage .218
Summary 225
Chapter 8 Animation 227
Using Bitmaps in Animation 227
Making Bitmaps .234
Displaying Movement .239
Summary 247
Chapter 9 Collision Detection 249
Basic Collisions .249
Bounding Circles 253
Distance between Points .253
Radii .255
Bounding Boxes .260
Pixel-Imperfect Collisions .268
Pixel-Perfect Collisions .272
Summary 274
Part III: Completing the Puzzle 275
Chapter 10 Handling Input 277
Handling the Keyboard .277
KeyDown() .278
KeyHit() .285
Mapping the Mouse to the Screen .294
Displaying the Mouse Cursor .295
What Was That? Handling Mouse Key Presses .298
The Middle Mouse Wheel .306
Handling Joystick Input .310
Summary 312
Trang 11Chapter 11 Sounds and Music 313
Sound .313
Loading Sounds .314
Listen Closely—Playing Sounds .316
Music .330
Channels and PlayMusic() .330
Messing With ’Da Channels .331
Summary 335
Chapter 12 Artificial Intelligence 337
Random Numbers 337
Creating a MilliSecs() Timer .342
Chasing and Evading .349
Chasing .349
Evading .354
Summary 356
Chapter 13 The Final Frontier: Invaderz!!! 359
Let’s Bust It: Planning the Game .359
Constants, Functions, and Types in Invaderz!!! .362
Playing Invaderz!!! .366
Epilogue .368
Part IV: Appendixes 371
Appendix A Scan Code Reference 373
Appendix B Useful Links 379
Blitz Basic Links .379
General Game Programming Links .380
Appendix C What’s on the CD 381
Source 382
Art .382
Sounds .382
Games 382
Programs .383
Index 384
Contents
X
Trang 12Hey, reader Thanks for buying my book I am really thankful for it
What is programming? Programming, according to Dictionary.com, is “a set of coded
instructions that enables a machine, especially a computer, to perform a desired sequence
of operations.” In other words, programming allows you to make your computer do
what-ever you want it to do Programming is used in what-everything related to the computer, but
there are many distinct flavors of programming This book teaches game programming.
Game programming is very different from the other types of programming When you
turn on your computer, you often see static programs—programs that sit there and wait
for you to do something Not with games Games are running constantly, and they don’t
need the player to do anything to keep it running
Of course, does this mean that game programming is a bit tougher than other styles of
programming? Yes and no Although game programming can be difficult at times, this
book strives to turn the difficult into second nature We use a language of programming
called BASIC, which, as you can probably guess, is pretty darn basic
What’s in the Book?
This book is meant to be a guide to teach any beginner how to design and develop games
Inside the book you will find a wealth of knowledge all written in mind to help you reach
the goal of making a game Each chapter builds on the previous chapters and makes the
book seem like a staircase—you move up step by step The last chapter helps use all of
your culminated knowledge in the production of a final game
Introduction
Trang 13Part I discusses the BlitzPlus language During this time, the book does not discuss
graph-ical programs, but instead uses text-based to get the language points across
Part II teaches the reader all about graphics within games There is such information as
varying colors, loading and displaying images, making scrolling backgrounds, and thingslike that
Part III examines other related parts to game programming The reader can learn how to
use keyboard input, sounds, and music, and take into account artificial intelligence Thispart also creates the final game that the book has been leading up to
Part IV contains all the appendixes for the book You will find all of the scan codes (for
han-dling input), a list of Web sites to further your knowledge in the field, and what is on the CD
Who Are You?
I suppose you can answer this question better than I, but let me tell you what I am ing for in a reader First of all, I am guessing that you are either a teenager who is inter-ested in game programming or a parent who is interested in having your child learn gameprogramming That is pretty much all that is required: interest This book is not set up to
look-be difficult It helps introduce the reader into the world of game programming
There are literally very few requirements All you really need is a basic knowledge of math,like addition, subtraction, multiplication, and division If you know those techniques, youare pretty much set! I also suggest that the reader asks his or her parent for help whenevernecessary I use some rudimentary algebra, but those instances are few and far between,and should be easy to comprehend
You don’t need to have any knowledge of other programming languages Not that it won’thelp if you do, of course If you do know any other languages, you can learn from this
book as well But, Game Programming for Teens, Second Edition teaches the language of
game programming along with the ability to actually implement games
If you are the parent of a child who wants to learn programming, this book is the way to
go General programming is a long and boring subject, but game programming allows your
child to create things that are fun Help your child with programming while he or she reads
this book, as well Not only will you both learn programming, but who knows, it maystrengthen the bond between parent and child (this comes from my psychologist side)
Who Am I?
Hey everybody, I am Maneesh Sethi I am a high school student, and the reason I am ing this book is because I believe that, because I am a teenager myself, I would be the bestone to help other teens learn about programming I began programming in 1999 in C and
writ-XII Introduction
Trang 14C++ Two years ago I discovered BlitzPlus and I have studied it ever since BlitzPlus seems
to be the easiest way for any novice to begin writing games, and I want to help the reader
progress as fast as possible The Web site for this book is located on
www.maneeshsethi.com, and you can e-mail me with any questions (before or after you
buy the book) at maneesh@maneeshsethi.com I love to get e-mails!
Conventions Used in This Book
n o t e
Notes provide additional information on a feature, extend an idea on how to do something, or
illus-trate a cool fact
c a u t i o n
Cautions warn you of potential problems and tell you what not to do
t i p
Tips give you some pertinent information on a better, faster, or easier way of doing something
Let’s Get Ready to Rumble…
If you are still browsing this book in the bookstore, now would be the time to take it
home The bookstore would probably appreciate it if you buy it first (so would I!)
The first part quickly teaches you all of the intricacies of the BlitzPlus programming language
And so we begin…
Introduction
Trang 15This page intentionally left blank
Trang 17Welcome to the amazing world of game programming! This book will show you
the ins and outs of video games and teach you to develop your own Gameprogramming is a huge topic, however, and we are going to hurry through theboring material in order to get to the fun stuff In other words, let's start right away!The easiest language for learning programming (at least in my opinion) is BASIC
BASIC stands for Beginner's All Purpose Symbolic Instruction Code, but that's not really
important BASIC is very easy to write and understand, and it's modeled after human language (it uses words instead of just numbers), so if you can speak English, you shouldn’t have a hard time with BASIC
We will be using a program called BlitzPlus in this book BlitzPlus is built to use a modified version of BASIC in its programming We begin with a short history of BASIC,just to get the ball rolling on the language