# Advanced Builds

For users of BSD, Linux, macOS, you can customize the image at
build time.

In the top level directory is a `package` directory containing
a file named `list`. You can add files to compile into your
system by adding them to the `list` and rebuilding.

Example:

If you have wanted to include the NumbersWithoutPrefixes.forth
example, add:

    ~~~
    'example/NumbersWithoutPrefixes.forth include
    ~~~

To the start of the `list` file and then run `make` again. The
newly built `bin/retro` will now include your additions.