anchor.diff:  
     enableParallelBuilding = true;
   
  -  makeFlags = [ "OPT=true"
  -                "RELEASE=true"
  -                "DATA_DIR=$(out)/share"
  -                "ENABLE_LOCAL_USER_DIR=true"
  -              ];
  +  makeFlags = [
  +    "OPT=true"
  +    "RELEASE=true"
  +    "DATA_DIR=$(out)/share"
  +    "ENABLE_LOCAL_USER_DIR=true"
  +    "NO_STEAMWORKS=true"
  +  ];
   
     installPhase = ''
       install -Dm755 keeper $out/bin/keeper
  
positive.code: 
        "nix-prefetch-url file://\$PWD/${name}".
      '';
      sha256 = "0115pxdzdyma2vicxgr0j21pp82gxdyrlj090s8ihp0b50f0nk53";
    } else null;
  
    sourceRoot = "source";
  
negative.code: { lib
  , stdenv
  , fetchFromGitHub
  , requireFile
  , openal
  , curl
  , libogg
  , libvorbis
  , SDL2
  , SDL2_image
  , zlib
  , clang
  , libtheora
  , unfree_assets ? false }:
  
  stdenv.mkDerivation rec {
    pname = "keeperrl";
    version = "alpha34";
  
    free-src = fetchFromGitHub {
      owner = "miki151";
      repo = "keeperrl";
      rev = version;
      sha256 = "sha256-0sww+ppctXvxMouclG3OdXpcNgrrOZJw9z8s2GhJ+IE=";
    };
  
    assets = if unfree_assets then requireFile rec {
  