{
  description = "It's Adventing Time";

  inputs.nixpkgs.url = "nixpkgs/nixos-unstable";

  outputs = {
    self,
    nixpkgs,
  }: let
    inherit (nixpkgs) lib;
    genSystems = lib.genAttrs [
      "x86_64-linux"
      "aarch64-linux"
    ];
    pkgsFor = nixpkgs.legacyPackages;
  in {
    devShells = genSystems (
      system: let
        pkgs = pkgsFor.${system};
      in {
        default = pkgs.mkShell {
          nativeBuildInputs = [
            pkgs.clang-tools
            (pkgs.sbcl.withPackages (p:
              with p; [
                alexandria
                cl-ppcre
                iterate
                split-sequence
                str
              ]))
            (pkgs.ghc.withPackages (p:
              with p; [
                containers
                extra
                regex-compat
                split
                text
                text-icu
                unordered-containers
                vector
              ]))
          ];
          CXXFLAGS = "-std=c++20 -Wall";
        };
      }
    );

    formatter = genSystems (system: pkgsFor.system.alejandra);
  };
}