The assembly code is written to be compiled with ca65, which is part
of the cc65 suite of tools (https://cc65.github.io/). On MacOS, the
tools can be installed using homebrew with brew install cc65.
The ROM images (drmario.nes for the original NTSC version, and
drmario_a.nes for NTSC revision A) can be compiled from source using
the included makefile with make all.
Running make test generates the ROM images and compares them with
the expected output.