adding a readme

README.md

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+# MS-DOS VGA Arena Shooter Game
+
+A Smash TV/Robotron-like game to help me learn a whole bunch of things
+about game programming, DOS & PC programming, x86 assembler & C, and VGA graphics!
+
+## Play!
+
+The latest build of the game is under Releases.
+[Send any feedback you wish](https://theindustriousrabbit.com/about) -- it's
+appreciated! -- but I really don't know when I'll get back to working on this.
+
+## Setup
+
+Builds are done on a host Linux system with Open Watcom 2.0 installed to
+a local directory. On my machine, that's `~/Applications/open-watcom-v2`.
+Tests and game are run in DOSBox-X.
+
+### Clone and build Open Watcom 2 for DOS cross-compilation
+
+You'll need to build Open Watcom 2 from source to get DOS compilation on Linux.
+[Follow the directions on their GitHub wiki](https://github.com/open-watcom/open-watcom-v2/wiki/Build).
+
+You may need DOSBox installed for the Open Watcom 2 build.
+
+### Modify `setup.sh` to use your local Open Watcom install
+
+Changing the path of `export WATCOM` should be enough
+
+### Install Ruby and the RMagick gem
+
+The spritesheet builder uses Ruby and RMagick to produce the x86 assembler
+spritesheets from `spritesheet.bmp`.
+
+### Install DOSBox-X
+
+I used [the Flatpak version](https://flathub.org/apps/com.dosbox_x.DOSBox-X) and created a wrapper script in my `PATH`:
+
+```sh
+#!/bin/sh
+
+flatpak run com.dosbox_x.DOSBox-X "$@"
+```
+
+### Try building the game & tests
+
+`bin/game` builds and runs `game.exe` and `bin/test` builds and runs the
+unit tests.
+
+## What's in here?
+
+### System access code
+
+Everything in the `system` folder is about directly accessing the PC hardware:
+
+* `keyboard.c` accepts keyboard input using a keyboard interrupt.
+* `mouse_io.c` accepts mouse input.
+* `pc_stuff.c` does various PC things with interrupts.
+* `vga.c` accesses the VGA card and has drawing routines built for
+  32-bit protected mode code and using the 320x200x256 chained VGA mode (mode 10h).
+
+### Unit tests
+
+I'm using the [CuTest](https://github.com/ennorehling/cutest) library to write basic unit tests for the game.
+I wanted to try out C unit testing and see what libraries could work on
+retro machines, and CuTest fit the bill. The tests run directly in DOS.
+
+### Compiled sprites
+
+I automated the pipeline to building compiled sprites from a bitmap file.
+Originally, I was doing memory copies from that bitmap file, and no matter
+how much I optimized them, they were slow slow slow. Having Ruby build the
+sprites as a series of `mov` instructions sped up the game immensely.
+
+### Inline assembler
+
+There's some non-trivial inline assembler in `system/vga.c` for drawing
+font glyhps. https://github.com/dhepper/font8x8 is the source of the
+font. I probably could have gotten the performance fast enough in pure C,
+but I really wanted to try some inline assembler.
+
+### Bitmap loading code
+
+Before switching to compiled sprites, I wrote code to load BMP files to
+a memory location of your choosing, as well as to extract the palette for
+feeding to the VGA card.
+
+### Open Watcom `wmake` Makefiles
+
+The `Makefile`s are not sophisticated, but it took me quite a while to
+research Open Watcom's slightly different syntax for `Makefiles`. The GNU
+make docs didn't help too much.
+
+## License
+
+MIT License on the code. If you use any code verbatim, or do anything else with this,
+let me know!
+
+CuTest has its own license.
+
+Any art that's not the spritesheet is (C) John Bintz, all rights reserved. That
+should only be the `chicken.bmp` file that's used as an example for
+bitmap loading code.

build.bat

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-wcc386.exe -q bmp_loader.c
-wcc386.exe -q mouse_io.c
-wcc386.exe -q pc_stuff.c
-wcc386.exe -q vga.c
-wcc386.exe -q keyboard.c
-wcl386.exe -q game.c bmp_load.obj mouse_io.obj pc_stuff.obj vga.obj keyboard.obj
-