You can simply clone the repository using Git, or if you just want to download this, click the `Clone or download` button up and to the right of this. This repo is also usable as a GitHub template for creating new repositories.
Make sure you have [RGBDS](https://github.com/rednex/rgbds), at least version 0.4.0, and GNU Make installed. Python 3 is required for the PB16 compressor bundled as a usage example, but that script is optional.
Everything in the `src` directory is the source, and can be freely modified however you want.
Any `.asm` files in that directory (and its sub-directories, recursively) will be individually assembled, automatically.
If you need some files not to be assembled directly (because they are only meant to be `INCLUDE`d), you can either rename them (typically, to `.inc`), or move them outside of `src` (typically, to a directory called `include`).
If you want to add resources, I recommend using the `src/assets` directory.
Add rules in the Makefile; an example is provided for compressing files using PB16 (a variation of [PackBits](https://wiki.nesdev.com/w/index.php/Tile_compression#PackBits)).
Pass the `-s` flag to `make` if it spews too much input for your tastes.
Päss the `-j <N>` flag to `make` to build more things in parallel, replacing `<N>` with however many things you want to build in parallel; your number of (logical) CPU cores is often a good pick (so, `-j 8` for me), run the command `nproc` to obtain it.
If you get errors that you don't understand, try running `make clean`.
If that gives the same error, try deleting the `assets` directory.
If that still doesn't work, try deleting the `bin` and `obj` directories as well.
If that still doesn't work, feel free to ask for help.
I recommend the [BGB](https://bgb.bircd.org) emulator for developing ROMs on Windows and, via Wine, Linux and macOS (64-bit build available for Catalina).
[SameBoy](https://github.com/LIJI32/SameBoy) is more accurate, but has a more lackluster interface outside of macOS.
