anchor.diff: -{ stdenv, fetchurl, cmake, curl, glew, makeWrapper, mesa, SDL2,
  +{ stdenv, lib, fetchurl, cmake, curl, glew, makeWrapper, mesa, SDL2,
     SDL2_image, unzip, wget, zlib, withOpenal ? true, openal ? null }:
   
   assert withOpenal -> openal != null;
  
positive.code:   '';
  
    nativeBuildInputs = 
      with stdenv.lib;
      [ cmake curl glew makeWrapper mesa SDL2 SDL2_image unzip wget zlib ]
      ++ optional withOpenal openal;
  
    cmakeFlags = [ "-DCMAKE_BUILD_TYPE=Release" "-DOPENSPADES_INSTALL_BINARY=bin" ];
  
  
negative.code:     unzip -u -o Resources/DevPaks27.zip -d Resources/DevPak
    '';
  
    NIX_CFLAGS_LINK = lib.optional withOpenal "-lopenal";
  
    meta = with stdenv.lib; {
      description = "A compatible client of Ace of Spades 0.75";
  