Derek Morris - Retro Game Dev: C64 Edition

DEREK MORRIS Copyright 2017 Retro Game Dev All rights reserved. To all the dreamers in life It is possible. TABLE OF CONTENTS Introduction......................................... 1 Why Develop for Retro Systems?............. 1 About This Book................................ 2 PART I: THE NECESSARY EVIL ............................... 3 Chapter 1: Numbers .................................. 4 Bases............................................ 4 Bits and Bytes.................................. 6 Uses.............................................. 7 Chapter 2: Commodore 64 Hardware............... 8 6510............................................. 8 VIC-II............................................. 9 SID............................................. 10 Memory........................................ 11 Chapter 3: 6502 Assembly Language.............. 12 Instructions.................................... 12 Addressing.................................... 14 Indexing....................................... 15 Flow Control................................... 15 PART II: STARTING TO PROGRAM ....................... 17 Chapter 4: I.D.E...................................... 18 Setup........................................... 19 First Program.................................. 23 Debugger...................................... 24 Chapter 5: Emulator............................... 27 Setup........................................... 27 Running a prg File............................ 28 Chapter 6: Code Framework....................... 29 Organization.................................. 29 Memory Layout............................... 30 Macros vs Subroutines....................... 31 BASIC Autoloader............................. 32 Character Sets................................. 32 Game Initialize................................ 34 Game Loop.................................... 34 PART III: LETS MAKE A SPACE SHOOTER ...... 37 Chapter 7: Create a Stellar Spaceship............. 38 Player Sprite................................... 38 Player Movement............................. 42 Chapter 8: Shoot the Bullets....................... 45 Software Sprites.............................. 45 Custom Characters........................... 48 Chapter 9: Start the Alien Invasion................. 51 Alien Sprites................................... 51 Alien Movement.............................. 54 Collisions...................................... 56 Chapter 10: Twinkle Twinkle Little Star........... 61 Custom Characters........................... 61 Star Movement................................ 62 Chapter 11: Let There Be Sound.................... 65 Execute Buffers............................... 65 Effects.......................................... 65 Chapter 12: Space Shooter Mini-Game............ 67 Game Flow.................................... 67 Scores and Lives.............................. 71 Memory Usage................................ 73 PART IV: LETS MAKE A PLATFORMER ............. 75 Chapter 13: Create a Cool Character.............. 76 Player Animation............................. 76 Player Movement............................. 77 Player Jumping............................... 80 Chapter 14: Add a Scrolling Background......... 83 Custom Characters........................... 83 Screen Map Data.............................. 84 Map Setup..................................... 87 Map Scrolling................................. 88 Collisions...................................... 91 Chapter 15: Pick Up the Pickups ................... 95 Collection...................................... 95 Reset........................................... 97 Chapter 16: Dig Up Those Pesky Worms........... 99 Enemy Animation............................ 99 Enemy Movement........................... 102 Chapter 17: Platformer Mini-Game............... 104 Timer......................................... 104 Death......................................... 105 Memory Usage............................... 106 PART V: RUNNING ON THE HARDWARE ....... 109 Chapter 18: What Do I Need?...................... 110 Computer.................................... 110 Display....................................... 112 Joystick....................................... 112 Storage....................................... 113 Fast Loader................................... 114 Chapter 19: Look, its On My TV................... 115 SD2IEC....................................... 115 Ultimate II.................................... 115 PART VI: FURTHER LEARNING ........................... 117 Chapter 20: Advanced Topics.................... 118 Chapter 21: Useful Resources and Wrap Up...... 119 Acknowledgements ............................... 120 Index .............................................. 121 Introduction Welcome to Retro Game Dev C64 Edition. 121 Introduction Welcome to Retro Game Dev C64 Edition.

Retro game systems from the 1980s hold a special place in my heart. Those early primitive games provided many hours of fun and amazement for a young child. A seed was planted in me that ultimately led to a long career in game development. The Commodore 64 is the largest selling home computer of all time with 17 million units sold worldwide, and decades later still boasts a thriving development community. Why Develop for Retro Systems? Retro games can be created on modern systems like a P.C. or a phone but usually a game engine is utilized that hides the complexities of the underlying hardware.

Its these very complexities that teach how to get the most out of the hardware while maximizing efficiency. Such valuable skills are highly sought after in the game industry. With the recent resurgence of retro games and the revamping of retro systems such as the NES Classic, SNES Classic, and C64 Mini, nows a great time to learn the inner workings of these systems and get your own games out there. Also, the availability of specialized retro game publishers means theres the possibility of having your creation released as a physical boxed product. How cool is that? About This Book This book is for those with a desire to create games for the Commodore 64. Whether youre a curious newcomer or are here for nostalgic reasons, I hope it provides a creative springboard that leads to more games for us all to enjoy.

Were privileged in this age of the internet that theres so much development information readily available, but it can be difficult to decipher, thus the aim of this book is to provide a concise guide to developing two mini-games: a space shooter and a platformer, but leave some more advanced features as a further learning exercise for the reader. Although the BASIC programming language is built into the Commodore 64, its operation is too slow for all but the most rudimentary of games, therefore well use assembly language. Assembly language is well documented elsewhere so this book will cover the basics but focus on the structure of the mini games and leave the reader to learn more about the assembly language code using suggested literature along with a full code base available to download. The development tools are P.C. only. The mini-games run on an emulator (various platforms) or a real Commodore 64/128.

Suggested Learning Process To get the most from this book I suggest the following steps: Download the assets from www.retrogamedev.com. Run some of the pre-built prgs (Commodore program files) in an emulator or on a real Commodore 64/128. Follow through the book trying the experiments and heeding the warnings. Experiment Warning! Study the supplied code base. Have fun! PART I: THE NECESSARY EVIL Chapter 1: Numbers The circuits contained within computers are designed to have two states: off and on (or low and high). These states are represented with different electronic voltage levels (usually 0V and 3.3V or 5V).