anchor.diff:      substituteInPlace Source/init.cpp --replace "/usr/share/diasurgical/devilutionx/" "${placeholder "out"}/share/diasurgical/devilutionx/"
   
       # download dependencies ahead of time
  -    substituteInPlace 3rdParty/asio/CMakeLists.txt --replace "https://github.com/diasurgical/asio/archive/ebeff99f539da23d27c2e8d4bdbc1ee011968644.tar.gz" "${asio}"
  -    substituteInPlace 3rdParty/SDL_audiolib/CMakeLists.txt --replace "https://github.com/realnc/SDL_audiolib/archive/aa79660eba4467a44f9dcaecf26b0f0a000abfd7.tar.gz" "${SDL_audiolib}"
  -    substituteInPlace 3rdParty/simpleini/CMakeLists.txt --replace "https://github.com/brofield/simpleini/archive/7bca74f6535a37846162383e52071f380c99a43a.zip" "${simpleini}"
  +    substituteInPlace 3rdParty/asio/CMakeLists.txt --replace "${asio.url}" "${asio}"
  +    substituteInPlace 3rdParty/libmpq/CMakeLists.txt --replace "${libmpq.url}" "${libmpq}"
  +    substituteInPlace 3rdParty/libsmackerdec/CMakeLists.txt --replace "${libsmackerdec.url}" "${libsmackerdec}"
  +    substituteInPlace 3rdParty/libzt/CMakeLists.txt \
  +      --replace "GIT_REPOSITORY https://github.com/diasurgical/libzt.git" "" \
  +      --replace "GIT_TAG ${libzt.rev}" "SOURCE_DIR ${libzt}"
  +    substituteInPlace 3rdParty/simpleini/CMakeLists.txt --replace "${simpleini.url}" "${simpleini}"
     '';
   
     cmakeFlags = [
       "-DBINARY_RELEASE=ON"
       "-DVERSION_NUM=${version}"
  -    "-DPACKET_ENCRYPTION=OFF" # FIXME: build with libsodium
  -    "-DDISABLE_ZERO_TIER=ON" # FIXME: build with libzt
     ];
   
     nativeBuildInputs = [
  
positive.code: 
  let
    # TODO: submit a PR upstream to allow system copies of these libraries where possible
    asio = fetchurl {
      url = "https://github.com/diasurgical/asio/archive/ebeff99f539da23d27c2e8d4bdbc1ee011968644.tar.gz";
      sha256 = "0vhb4cig40mm0a98i74grpmfkcmby8zxg6vqa38dpryxpgvp5fw8";
    };
  
    SDL_audiolib = fetchurl {
      url = "https://github.com/realnc/SDL_audiolib/archive/aa79660eba4467a44f9dcaecf26b0f0a000abfd7.tar.gz";
      sha256 = "0z4rizncp6gqsy72b3709zc9fr915wgcwnlx1fhhy7mrczsly630";
    };
  
    simpleini = fetchzip {
      url = "https://github.com/brofield/simpleini/archive/7bca74f6535a37846162383e52071f380c99a43a.zip";
      sha256 = "07kf1jjbc9v04hsysa6v2wh1m9csf5qz0b1wmlkf9sj00kf47zj7";
    };
  in
  
  stdenv.mkDerivation rec {
    pname = "devilutionx";
    version = "1.3.0";
  
    src = fetchFromGitHub {
      owner = "diasurgical";
      repo = "devilutionX";
      rev = version;
      sha256 = "0acrkqi0pr3cbr5i1a1vfrnxv1n3xmql5d86bm2gywvpdb94xads";
    };
  
    patches = [
      # allow building with system SDL2_image instead of vendored version
      # this patch can be removed on the next release of devilutionx
      # see https://github.com/diasurgical/devilutionX/pull/3386
      (fetchpatch {
        url = "https://github.com/diasurgical/devilutionX/commit/41ff03e94c02477bffb2d62764e8624c0e06854d.patch";
        sha256 = "1lrnb9d0dcdyd78rix5rl4p8kkwbnl91llr9fgb86ysm3q58qkvj";
      })
    ];
  
  
negative.code: , fetchFromGitHub
  , fetchpatch
  , fetchurl
  , bzip2
  , cmake
  , pkg-config
  , gettext
  , libsodium
  , SDL2
  , SDL_audiolib
  , SDL2_image
  , fmt
  , libpng
  