Making Games with Python & PyGame.pdf(with code)

T ABLE OF C ONTENTS Who is this book for? ........................................................................................................................ i About This Book .............................................................................................................................. ii Chapter 1 – Installing Python and Pygame ...................................................................................... 1 What You Should Know Before You Begin ................................................................................ 1 Downloading and Installing Python ............................................................................................. 1 Windows Instructions .................................................................................................................. 1 Mac OS X Instructions ................................................................................................................. 2 Ubuntu and Linux Instructions .................................................................................................... 2 Starting Python............................................................................................................................. 2 Installing Pygame......................................................................................................................... 3 How to Use This Book ................................................................................................................. 4 The Featured Programs ................................................................................................................ 4 Downloading Graphics and Sound Files ...................................................................................... 4 Line Numbers and Spaces ............................................................................................................ 4 Text Wrapping in This Book ....................................................................................................... 5 Checking Your Code Online ........................................................................................................ 6 More Info Links on http://invpy.com ........................................................................................... 6 Chapter 2 – Pygame Basics .............................................................................................................. 7 GUI vs. CLI ................................................................................................................................. 7 Source Code for Hello World with Pygame ................................................................................ 7 Setting Up a Pygame Program ..................................................................................................... 8 Game Loops and Game States ................................................................................................... 10 pygame.event.Event Objects ........................................................................................... 11 The QUIT Event and pygame.quit() Function .................................................................. 12 Pixel Coordinates ....................................................................................................................... 13iv http://inventwithpython.com/pygame A Reminder About Functions, Methods, Constructor Functions, and Functions in Modules (and the Difference Between Them) .................................................................................................. 14 Surface Objects and The Window ............................................................................................. 15 Colors ......................................................................................................................................... 16 Transparent Colors ..................................................................................................................... 17 pygame.Color Objects .......................................................................................................... 18 Rect Objects ............................................................................................................................... 18 Primitive Drawing Functions ..................................................................................................... 20 pygame.PixelArray Objects .............................................................................................. 23 The pygame.display.update() Function ...................................................................... 24 Animation .................................................................................................................................. 24 Frames Per Second and pygame.time.Clock Objects ....................................................... 27 Drawing Images with pygame.image.load() and blit() ............................................ 28 Fonts ........................................................................................................................................... 28 Anti-Aliasing.............................................................................................................................. 30 Playing Sounds........................................................................................................................... 31 Summary .................................................................................................................................... 32 Chapter 3 – Memory Puzzle .......................................................................................................... 33 How to Play Memory Puzzle ..................................................................................................... 33 Nested for Loops ..................................................................................................................... 33 Source Code of Memory Puzzle ................................................................................................ 34 Credits and Imports .................................................................................................................... 42 Magic Numbers are Bad ............................................................................................................ 42 Sanity Checks with assert Statements ................................................................................... 43 Telling If a Number is Even or Odd .......................................................................................... 44 Crash Early and Crash Often! .................................................................................................... 44 Making the Source Code Look Pretty ........................................................................................ 45 Using Constant Variables Instead of Strings ............................................................................. 46 Making Sure We Have Enough Icons ........................................................................................ 47 Tuples vs. Lists, Immutable vs. Mutable ................................................................................... 47 Email questions to the author: al@inventwithpython.comAbout This Book v One Item Tuples Need a Trailing Comma ................................................................................. 48 Converting Between Lists and Tuples ....................................................................................... 49 The global statement, and Why Global Variables are Evil.................................................... 49 Data Structures and 2D Lists ..................................................................................................... 51 The ―Start Game‖ Animation ..................................................................................................... 52 The Game Loop ......................................................................................................................... 52 The Event Handling Loop .......................................................................................................... 53 Checking Which Box The Mouse Cursor is Over ..................................................................... 54 Handling the First Clicked Box ................................................................................................. 55 Handling a Mismatched Pair of Icons ........................................................................................ 56 Handling If the Player Won ....................................................................................................... 56 Drawing the Game State to the Screen ...................................................................................... 57 Creating the ―Revealed Boxes‖ Data Structure ......................................................................... 58 Creating the Board Data Structure: Step 1 – Get All Possible Icons ......................................... 58 Step 2 – Shuffling and Truncating the List of All Icons ............................................................ 59 Step 3 – Placing the Icons on the Board .................................................................................... 59 Splitting a List into a List of Lists.............................................................................................. 60 Different Coordinate Systems .................................................................................................... 61 Converting from Pixel Coordinates to Box Coordinates ........................................................... 62 Drawing the Icon, and Syntactic Sugar ...................................................................................... 63 Syntactic Sugar with Getting a Board Space’s Icon’s Shape and Color .................................... 64 Drawing the Box Cover ............................................................................................................. 64 Handling the Revealing and Covering Animation ..................................................................... 65 Drawing the Entire Board .......................................................................................................... 66 Drawing the Highlight ............................................................................................................... 67 The ―Start Game‖ Animation ..................................................................................................... 67 Revealing and Covering the Groups of Boxes ........................................................................... 68 The ―Game Won‖ Animation .................................................................................................... 68 Telling if the Player Has Won ................................................................................................... 69vi http://inventwithpython.com/pygame Why Bother Having a main() Function? ................................................................................ 69 Why Bother With Readability? .................................................................................................. 70 Summary, and a Hacking Suggestion ........................................................................................ 74 Chapter 4 – Slide Puzzle ................................................................................................................ 77 How to Play Slide Puzzle ........................................................................................................... 77 Source Code to Slide Puzzle ...................................................................................................... 77 Second Verse, Same as the First ................................................................................................ 85 Setting Up the Buttons ............................................................................................................... 86 Being Smart By Using Stupid Code .......................................................................................... 87 The Main Game Loop ................................................................................................................ 88 Clicking on the Buttons ............................................................................................................. 89 Sliding Tiles with the Mouse ..................................................................................................... 90 Sliding Tiles with the Keyboard ................................................................................................ 90 ―Equal To One Of‖ Trick with the in Operator ........................................................................ 91 WASD and Arrow Keys ............................................................................................................ 91 Actually Performing the Tile Slide ............................................................................................ 92 IDLE and Terminating Pygame Programs ................................................................................. 92 Checking for a Specific Event, and Posting Events to Pygame’s Event Queue ........................ 92 Creating the Board Data Structure ............................................................................................. 93 Not Tracking the Blank Position ................................................................................................ 94 Making a Move by Updating the Board Data Structure ............................................................ 94 When NOT to Use an Assertion ................................................................................................ 95 Getting a Not-So-Random Move ............................................................................................... 96 Converting Tile Coordinates to Pixel Coordinates .................................................................... 97 Converting from Pixel Coordinates to Board Coordinates ........................................................ 97 Drawing a Tile ........................................................................................................................... 97 The Making Text Appear on the Screen .................................................................................... 98 Drawing the Board ..................................................................................................................... 99 Drawing the Border of the Board ............................................................................................... 99 Email questions to the author: al@inventwithpython.comAbout This Book vii Drawing the Buttons ................................................................................................................ 100 Animating the Tile Slides ........................................................................................................ 100 The copy() Surface Method ................................................................................................. 101 Creating a New Puzzle ............................................................................................................. 103 Animating the Board Reset ...................................................................................................... 104 Time vs. Memory Tradeoffs .................................................................................................... 105 Nobody Cares About a Few Bytes ........................................................................................... 106 Nobody Cares About a Few Million Nanoseconds .................................................................. 107 Summary .................................................................................................................................. 107 Chapter 5 – Simulate .................................................................................................................... 108 How to Play Simulate .............................................................................................................. 108 Source Code to Simulate .......................................................................................................... 108 The Usual Starting Stuff .......................................................................................................... 114 Setting Up the Buttons ............................................................................................................. 115 The main() Function ............................................................................................................. 115 Some Local Variables Used in This Program .......................................................................... 116 Drawing the Board and Handling Input ................................................................................... 117 Checking for Mouse Clicks ..................................................................................................... 118 Checking for Keyboard Presses ............................................................................................... 118 The Two States of the Game Loop .......................................................................................... 119 Figuring Out if the Player Pressed the Right Buttons .............................................................. 119 Epoch Time .............................................................................................................................. 121 Drawing the Board to the Screen ............................................................................................. 122 Same Old terminate() Function ....................................................................................... 122 Reusing The Constant Variables .............................................................................................. 123 Animating the Button Flash ..................................................................................................... 123 Drawing the Buttons ................................................................................................................ 126 Animating the Background Change ......................................................................................... 126 The Game Over Animation ...................................................................................................... 127viii http://inventwithpython.com/pygame Converting from Pixel Coordinates to Buttons ........................................................................ 129 Explicit is Better Than Implicit ................................................................................................ 129 Chapter 6 – Wormy ...................................................................................................................... 131 How to Play Wormy ................................................................................................................ 131 Source Code to Wormy ............................................................................................................ 131 The Grid ................................................................................................................................... 137 The Setup Code ........................................................................................................................ 137 The main() Function ............................................................................................................. 138 A Separate runGame() Function .......................................................................................... 139 The Event Handling Loop ........................................................................................................ 139 Collision Detection .................................................................................................................. 140 Detecting Collisions with the Apple ........................................................................................ 141 Moving the Worm .................................................................................................................... 142 The insert() List Method................................................................................................... 142 Drawing the Screen .................................................................................................................. 143 Drawing ―Press a key‖ Text to the Screen ............................................................................... 143 The checkForKeyPress() Function ................................................................................ 143 The Start Screen ....................................................................................................................... 144 Rotating the Start Screen Text ................................................................................................. 145 Rotations Are Not Perfect ........................................................................................................ 146 Deciding Where the Apple Appears ........................................................................................ 147 Game Over Screens .................................................................................................................. 147 Drawing Functions ................................................................................................................... 148 Don’t Reuse Variable Names ................................................................................................... 151 Chapter 7 - Tetromino .................................................................................................................. 153 How to Play Tetromino ............................................................................................................ 153 Some Tetromino Nomenclature ............................................................................................... 153 Source Code to Tetromino ....................................................................................................... 154 The Usual Setup Code ............................................................................................................. 166 Email questions to the author: al@inventwithpython.comAbout This Book ix Setting up Timing Constants for Holding Down Keys ............................................................ 166 More Setup Code ..................................................................................................................... 166 Setting Up the Piece Templates ............................................................................................... 168 Splitting a ―Line of Code‖ Across Multiple Lines ................................................................... 171 The main() Function ............................................................................................................. 172 The Start of a New Game ......................................................................................................... 173 The Game Loop ....................................................................................................................... 174 The Event Handling Loop ........................................................................................................ 174 Pausing the Game .................................................................................................................... 174 Using Movement Variables to Handle User Input ................................................................... 175 Checking if a Slide or Rotation is Valid .................................................................................. 175 Finding the Bottom .................................................................................................................. 178 Moving by Holding Down the Key.......................................................................................... 179 Letting the Piece ―Naturally‖ Fall ............................................................................................ 182 Drawing Everything on the Screen .......................................................................................... 182 makeTextObjs() , A Shortcut Function for Making Text .................................................. 183 The Same Old terminate() Function ................................................................................ 183 Waiting for a Key Press Event with the checkForKeyPress() Function ........................ 183 showTextScreen() , A Generic Text Screen Function ..................................................... 184 The checkForQuit() Function .......................................................................................... 185 The calculateLevelAndFallFreq() Function .......................................................... 185 Generating Pieces with the getNewPiece() Function ....................................................... 188 Adding Pieces to the Board Data Structure ............................................................................. 189 Creating a New Board Data Structure ...................................................................................... 189 The isOnBoard() and isValidPosition() Functions ............................................... 190 Checking for, and Removing, Complete Lines ........................................................................ 192 Convert from Board Coordinates to Pixel Coordinates ........................................................... 195 Drawing a Box on the Board or Elsewhere on the Screen ....................................................... 195 Drawing Everything to the Screen ........................................................................................... 196x http://inventwithpython.com/pygame Drawing the Score and Level Text .......................................................................................... 196 Drawing a Piece on the Board or Elsewhere on the Screen ..................................................... 197 Drawing the ―Next‖ Piece ........................................................................................................ 197 Summary .................................................................................................................................. 198 Chapter 8 – Squirrel Eat Squirrel ................................................................................................. 200 How to Play Squirrel Eat Squirrel............................................................................................ 200 The Design of Squirrel Eat Squirrel ......................................................................................... 200 Source Code to Squirrel Eat Squirrel ....................................................................................... 201 The Usual Setup Code ............................................................................................................. 211 Describing the Data Structures ................................................................................................ 212 The main() Function ............................................................................................................. 213 The pygame.transform.flip() Function .................................................................... 214 A More Detailed Game State than Usual ................................................................................. 214 The Usual Text Creation Code................................................................................................. 215 Cameras ................................................................................................................................... 215 The ―Active Area‖ ................................................................................................................... 217 Keeping Track of the Location of Things in the Game World ................................................ 218 Starting Off with Some Grass .................................................................................................. 219 The Game Loop ....................................................................................................................... 219 Checking to Disable Invulnerability ........................................................................................ 219 Moving the Enemy Squirrels ................................................................................................... 219 Removing the Far Away Grass and Squirrel Objects .............................................................. 221 When Deleting Items in a List, Iterate Over the List in Reverse ............................................. 221 Adding New Grass and Squirrel Objects ................................................................................. 223 Camera Slack, and Moving the Camera View ......................................................................... 223 Drawing the Background, Grass, Squirrels, and Health Meter ................................................ 224 The Event Handling Loop ........................................................................................................ 226 Moving the Player, and Accounting for Bounce ...................................................................... 228 Collision Detection: Eat or Be Eaten ....................................................................................... 229 Email questions to the author: al@inventwithpython.comAbout This Book xi The Game Over Screen ............................................................................................................ 231 Winning ................................................................................................................................... 232 Drawing a Graphical Health Meter .......................................................................................... 232 The Same Old terminate() Function ................................................................................ 232 The Mathematics of the Sine Function .................................................................................... 233 Backwards Compatibility with Python Version 2 .................................................................... 236 The getRandomVelocity() Function .............................................................................. 237 Finding a Place to Add New Squirrels and Grass .................................................................... 237 Creating Enemy Squirrel Data Structures ................................................................................ 238 Flipping the Squirrel Image ..................................................................................................... 239 Creating Grass Data Structures ................................................................................................ 239 Checking if Outside the Active Area ....................................................................................... 240 Summary .................................................................................................................................. 241 Chapter 9 – Star Pusher ................................................................................................................ 242 How to Play Star Pusher .......................................................................................................... 242 Source Code to Star Pusher ...................................................................................................... 242 The Initial Setup ....................................................................................................................... 256 Data Structures in Star Pusher ................................................................................................. 271 The ―Game State‖ Data Structure ............................................................................................ 271 The ―Map‖ Data Structure ....................................................................................................... 271 The ―Levels‖ Data Structure .................................................................................................... 272 Reading and Writing Text Files ............................................................................................... 272 Text Files and Binary Files ...................................................................................................... 272 Writing to Files ........................................................................................................................ 273 Reading from Files ................................................................................................................... 274 About the Star Pusher Map File Format .................................................................................. 274 Recursive Functions ................................................................................................................. 280 Stack Overflows ....................................................................................................................... 281 Preventing Stack Overflows with a Base Case ........................................................................ 283xii http://inventwithpython.com/pygame The Flood Fill Algorithm ......................................................................................................... 284 Drawing the Map ..................................................................................................................... 285 Checking if the Level is Finished ............................................................................................ 287 Summary .................................................................................................................................. 288 Chapter 10 – Four Extra Games ................................................................................................... 289 Flippy, an ―Othello‖ Clone ...................................................................................................... 290 Source Code for Flippy ............................................................................................................ 292 Ink Spill, a ―Flood It‖ Clone .................................................................................................... 305 Source Code for Ink Spill ........................................................................................................ 305 Four-In-A-Row, a ―Connect Four‖ Clone ................................................................................ 317 Source Code for Four-In-A-Row ............................................................................................. 317 Gemgem, a ―Bejeweled‖ Clone ............................................................................................... 327 Source Code for Gemgem ........................................................................................................ 327 Summary .................................................................................................................................. 340 Glossary ....................................................................................................................................... 342 About the Author ......................................................................................................................... 347