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4f4c5c6218
Updated for the fact that the apple2 version is in penetrator-apple2 and not just penetrator
134 lines
5.2 KiB
Markdown
134 lines
5.2 KiB
Markdown
# penetrator
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Remake of the ZX Spectrum game for the Apple II.
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1. INTRODUCTION
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This is a "port" of the Commander X16 version that's also in my repo's as just
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penetrator. I had to rewrite quite a bit of the drawing code and make some
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other changes to make it work on the Apple II, and to make it fast enough.
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This is also my very first program for the Apple II. It was a learning
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experience :)
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2. CURRENT STATUS
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The game is a pretty good replica of the original. It is missing sound. It's
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also missing the demo attract mode, and the fireworks.
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3. TECHNICAL DETAILS
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The game is written in 6502 assembly using the ca65 assembler.
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The other interesting thing about the original is that it ran the AI and user
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input twice for every world move. This version does not do it the same way. The
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bullet update ran twice for each world update but now that the world moves while
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the bullets move twice, the bullets could pass through the walls. To fix this
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issue, I have made the bullets 50% longer.
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4. KEYS and JOYSTICK
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The Apple 2 gameplay works only with a joystick since you cannot detect multiple
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keys down on the Apple II. The UI works with the keyboard or joystick and the
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world editor uses both.
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The menus all show the keys to advance. There's also a help screen in the
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editor.
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5. THE FILES
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I tried to comment all the code very thoroughly in the CX16 version. Since this
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version is derived from that version, the code is also well documented, but to
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be honest, the comments may not always be accurate. I did not do a pass to see
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if they are accurate.
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There are actually 2 programs in this. The 1st is the game, and it's in
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src/apple2.
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* defs.inc - Constants and definitions used throughout
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* draw.inc - VERA layer drawing. drawSprite, for example
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* edit.inc - The built-in world editor
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* file.inc - Load and Save code
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* fontdata.inc - A ZX Spectrum font in 16x8
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* game.inc - The in-game logic, AI etc. The bulk of the "game"
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* input.inc - User controls for game and editor
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* logo.hgr - 8Kb splash screen in HGR format
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* logo.inc - file that simply does an incbin on logo.hgr
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* logodata.inc - Line data for writing Penetrator and logo image data
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* macros.inc - print macros mostly
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* penetrator.asm - Where the game starts, initial setup, etc.
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* penetrator.cfg - ca65 configuration file
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* rodata.inc - Read-only data such as lookup tables, sprites etc.
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* terrain.inc - The terrain drawing routines
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* text.inc - In game text and print functions
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* trndata.inc - The world data (triplet - top, bottom and enemy pos)
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* ui.inc - User facing screens, name input, etc.
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* variables.inc - All non zero page variables
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* zpvars.inc - The zero page variables
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The second is the ProDos loader that will auto-load the game. It's in the
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src/apple2.loader folder. It has these files (all provided to me by Oliver
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Schmidt)
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* loader.cfg - ca65 configuration file
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* loader.s - file to load and start the game
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6. BUILDING THE GAME
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Making the game has a few steps. Use make and the Makefile on all OSs, that would be the easiest.
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Start by making the loader - this needs to be done once only.
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make TARGETS=apple2.loader
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Next, make the game with:
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make
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The next step is to make a bootable disk image. For this, you will need some
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other piece of 3rd party software. It's called AppleCommander. Once
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downloaded, put it in the apple2 folder in the root (apple2 folder at same level
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as Makefile). This software will put the loader and game into the disk image.
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Since I use Windows to develop, I have a file called build.cmd next to the
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Makefile (and checked in here as well). The contents of this file is listed
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below (where the line ends with "\\" isn't actually a line-end, I just cut the
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line there for readability, the next line is actually on the same line as the
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line ending with "\\").
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copy apple2\\template.dsk Penetrator.dsk
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java -jar apple2\AppleCommander-win64-1.5.0.jar -p Penetrator.dsk \\
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penetrat.system sys < penetrator-apple2.apple2.loader
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java -jar apple2\AppleCommander-win64-1.5.0.jar -as Penetrator.dsk \\
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penetrat bin < penetrator-apple2.apple2
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apple2\\Applewin.exe -d1 penetrator.dsk
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You will need to install Java to use AppleCommander. The apple2/template.dsk is
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a "blank ProDos floppy" that has the loader and the game placed on it by
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AppleCommander. I use the AppleWin emulator to run the game (-d1 penetrator.dsk
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mounts the floppy in drive one, and then boots from it automatically). In
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powershell, when developing the game, I would just use this command to do it
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all:
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make; .\\build.cmd
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Find AppleCommander here (I used Version 1.5.0):
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https://github.com/AppleCommander/AppleCommander/releases
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Find AppleWin here:
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https://github.com/AppleWin/AppleWin/releases
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7. CREDITS
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* Phillip Mitchell and Beam Software for creating and publishing the game in
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1982.
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* A special call-out to Oliver Schmidt who provided me with invaluable
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assistance to get me going on the Apple II.
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* Everyone involved in the Apple II projects (AppleWin | AppleCommander).
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* Everyone involved in making the cc65 tools, it's very good.
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8. CONTACT
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Feel free to contact me at swessels@email.com if you have thoughts or
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suggestions.
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Thank you
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Stefan Wessels
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16 December 2019 - Initial Revision
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