Struggling with nix

flake.nix

{
  inputs = {
      nixpkgs.url                         = "github:nixos/nixpkgs/nixpkgs-unstable";
      nixpkgs.follows                     = "nix/nixpkgs";
     # debug.url                            
     nguix.url                            = "github:sauricat/nguix";
     nguix.follows                        = "nix/nixpkgs";
     #stdenv.url 
  };


  outputs = { self, nix, nixpkgs, nguix } : 
    let 
      # Generate a u  ser-friendly version number.
      version           = builtins.substring 0 8 self.lastModifiedDate;
      # System types to support.>
      supportedSystems  = [ "x86_64-linux" "x86_64-darwin" "aarch64-linux" "aarch64-darwin" ];

      # Nixpkgs instantiated for supported system types.
      forAllSystems     = nixpkgs.lib.genAttrs supportedSystems;
      nixpkgsFor        = forAllSystems (system: import nixpkgs { inherit system; });
    in{
      packages = forAllSystems (system: 
        let 
          pkgs = nixpkgsFor.${system};
        in{
          default = pkgs.stdenv.mkDerivation {
            name = "hello";
            src = self;
            buildPhase = "nguix --version";
            installPhase = "mkdir -p $out/bin; install -t $out/bin hello";
          };
        }
      );

    };      
}