134 lines
4.4 KiB
Markdown
134 lines
4.4 KiB
Markdown
# DOS VGA Arena Shooter Game
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A Smash TV/Robotron-like game to help me learn a whole bunch of things
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about game programming, DOS & PC programming, x86 assembler & C, and VGA graphics!
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[Video of the game in action here!](https://makertube.net/w/1iQ7YYFkQjFmjuMy72Msqp)
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## Play!
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The latest build of the game is under Releases.
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[Send any feedback you wish](https://theindustriousrabbit.com/about) -- it's
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appreciated! -- but I really don't know when I'll get back to working on this.
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Use WASD to move, left mouse to fire, aim using your mouse. Shooting enemies
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restores health and gives you coins. If you earn enough coins, you can upgrade:
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* `P` will increase damage per shot
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* `O` permanently upgrades your max health and restores all your health
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* `I` will increase the amount of health you can get from shooting enemies
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There are two weapon pickups:
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* Yellow is a shotgun, firing a spread of three shots
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* Red doubles up your shots, potentially making it through more enemies
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Much of it is not working:
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* The game just starts.
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* The game doesn't end when you run out of health. Hit [Escape] to end the game.
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* The difficulty needs serious tuning.
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* It does not look good.
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* If you play for too long the game will likely crash.
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Try it out!
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## Setup
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Builds are done on a host Linux system with Open Watcom 2.0 installed to
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a local directory. On my machine, that's `~/Applications/open-watcom-v2`.
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Tests and game are run in DOSBox-X.
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### Clone and build Open Watcom 2 for DOS cross-compilation
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You'll need to build Open Watcom 2 from source to get DOS compilation on Linux.
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[Follow the directions on their GitHub wiki](https://github.com/open-watcom/open-watcom-v2/wiki/Build).
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You may need DOSBox installed for the Open Watcom 2 build.
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### Modify `setup.sh` to use your local Open Watcom install
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Changing the path of `export WATCOM` should be enough
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### Install Ruby and the RMagick gem
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The spritesheet builder uses Ruby and RMagick to produce the x86 assembler
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spritesheets from `spritesheet.bmp`.
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### Install DOSBox-X
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I used [the Flatpak version](https://flathub.org/apps/com.dosbox_x.DOSBox-X) and created a wrapper script in my `PATH`:
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```sh
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#!/bin/sh
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flatpak run com.dosbox_x.DOSBox-X "$@"
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```
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### Try building the game & tests
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`bin/game` builds and runs `game.exe` and `bin/test` builds and runs the
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unit tests.
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### Make a release
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`bin/release` makes `release.zip` which contains the game and the DOS/4GW
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wrapper.
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## What's in here?
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### System access code
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Everything in the `system` folder is about directly accessing the PC hardware:
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* `keyboard.c` accepts keyboard input using a keyboard interrupt.
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* `mouse_io.c` accepts mouse input.
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* `pc_stuff.c` does various PC things with interrupts.
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* `vga.c` accesses the VGA card and has drawing routines built for
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32-bit protected mode code and using the 320x200x256 chained VGA mode (mode 10h).
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### Unit tests
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I'm using the [CuTest](https://github.com/ennorehling/cutest) library to write basic unit tests for the game.
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I wanted to try out C unit testing and see what libraries could work on
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retro machines, and CuTest fit the bill. The tests run directly in DOS.
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### Compiled sprites
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I automated the pipeline to building compiled sprites from a bitmap file.
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Originally, I was doing memory copies from that bitmap file, and no matter
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how much I optimized them, they were slow slow slow. Having Ruby build the
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sprites as a series of `mov` instructions sped up the game immensely.
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### Inline assembler
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There's some non-trivial inline assembler in `system/vga.c` for drawing
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font glyphs. https://github.com/dhepper/font8x8 is the source of the
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font. I probably could have gotten the performance fast enough in pure C,
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but I really wanted to try some inline assembler.
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### Bitmap loading code
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Before switching to compiled sprites, I wrote code to load BMP files to
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a memory location of your choosing, as well as to extract the palette for
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feeding to the VGA card.
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### Open Watcom `wmake` Makefiles
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The `Makefile`s are not sophisticated, but it took me quite a while to
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research Open Watcom's slightly different syntax for `Makefiles`. The GNU
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make docs didn't help too much.
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## License
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MIT License on the code. If you use any code verbatim, or do anything else with this,
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let me know!
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CuTest has its own license.
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Any art that's not the spritesheet is (C) John Bintz, all rights reserved. That
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should only be the `chicken.bmp` file that's used as an example for
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bitmap loading code.
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