{
  description = "advent_of_code";

  inputs = {
    nixpkgs.url = "github:nixos/nixpkgs/nixpkgs-unstable";
  };

  outputs = {
    self,
    nixpkgs,
  }: let
    forAllSystems = function:
      nixpkgs.lib.genAttrs nixpkgs.lib.systems.flakeExposed (
        system: function nixpkgs.legacyPackages.${system}
      );
  in {
    #packages = forAllSystems (pkgs: {
    #  example = pkgs.callPackage ./default.nix { };
    #  default = self.packages.${pkgs.stdenv.hostPlatform.system}.example;
    #});

    devShells = forAllSystems (pkgs: {
      default = pkgs.callPackage ./shell.nix {inherit pkgs;};
    });

    #overlays.default = final: _: {example = final.callPackage ./default.nix {};};
  };
}