anchor.diff:    dontUnpack = true;
   
     installPhase = with systemSpecific; ''
  +    runHook preInstall
  +
       install -Dm644 $src $out/share/fonts/truetype/${fontFile}
  +
  +    runHook postInstall
     '';
   
     meta = with stdenv.lib; {
  
positive.code:       of files ranging from png, svg, iconjar, sprites, and fonts.
      '';
      homepage = "https://www.joypixels.com/fonts";
      license = let free-license = joypixels-free-license;
                    appendix = joypixels-license-appendix;
        in with systemSpecific; {
          spdxId = "LicenseRef-JoyPixels-Free-6.0-with-${capitalized}-Appendix";
          fullName = "${free-license.fullName} with ${appendix.fullName}";
  
negative.code: { stdenv
  , fetchurl
  , config
  , acceptLicense ? config.joypixels.acceptLicense or false
  }:
  
  let
    inherit (stdenv.hostPlatform.parsed) kernel;
  
    systemSpecific = {
      darwin = rec {
        systemTag =  "nix-darwin";
        capitalized = systemTag;
        fontFile = "JoyPixels-SBIX.ttf";
      };
    }.${kernel.name} or rec {
      systemTag = "nixos";
      capitalized = "NixOS";
      fontFile = "joypixels-android.ttf";
    };
  
    joypixels-free-license = with systemSpecific; {
      spdxId = "LicenseRef-JoyPixels-Free-6.0";
      fullName = "JoyPixels Free License Agreement 6.0";
      url = "https://cdn.joypixels.com/distributions/${systemTag}/license/free-license.pdf";
      free = false;
    };
  
    joypixels-license-appendix = with systemSpecific; {
      spdxId = "LicenseRef-JoyPixels-NixOS-Appendix";
      fullName = "JoyPixels ${capitalized} License Appendix";
      url = "https://cdn.joypixels.com/distributions/${systemTag}/appendix/joypixels-license-appendix.pdf";
      free = false;
    };
  
    throwLicense = throw ''
      Use of the JoyPixels font requires acceptance of the license.
        - ${joypixels-free-license.fullName} [1]
        - ${joypixels-license-appendix.fullName} [2]
  
      You can express acceptance by setting acceptLicense to true in your
      configuration. Note that this is not a free license so it requires allowing
      unfree licenses.
  
      configuration.nix:
        nixpkgs.config.allowUnfree = true;
        nixpkgs.config.joypixels.acceptLicense = true;
  
      config.nix:
        allowUnfree = true;
        joypixels.acceptLicense = true;
  
      [1]: ${joypixels-free-license.url}
      [2]: ${joypixels-license-appendix.url}
    '';
  
  in
  
  