{
  inputs = {
    nixpkgs.url = "nixpkgs/nixos-unstable";
  };
  outputs = { nixpkgs, ... }:
    let
      systems = [ "x86_64-linux" "aarch64-linux" "x86_64-darwin" "aarch64-darwin" ];
      foreachSystem = nixpkgs.lib.genAttrs systems;
    in
    {
      packages = foreachSystem (system:
        let
          pkgs = import nixpkgs { inherit system; };
        in
        rec {
          hello = pkgs.callPackage ./default.nix { };

          default = hello;
        });
      devShells = foreachSystem
        (system:
          let
            pkgs = import nixpkgs { inherit system; };
          in
          with pkgs;  {
            default = pkgs.callPackage ./shell.nix { };
          });
    };
}