{
  description = "Advent of Code 2023";

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

  outputs = { self, nixpkgs, flake-utils }:
    flake-utils.lib.eachDefaultSystem (system:
      let
        inherit (nixpkgs) lib;
        pkgs = import nixpkgs { inherit system; };
        zig = pkgs.zig_0_11;
      in
      {
        devShells = {
          default = pkgs.mkShellNoCC {
            buildInputs = [ zig pkgs.zls ];
          };
          ci = pkgs.mkShellNoCC {
            buildInputs = [ zig ];
          };
        };

        packages.default =
          let
            optimize = "ReleaseSafe";
          in
          pkgs.stdenv.mkDerivation {
            name = "aoc23";
            src = lib.cleanSource ./.;

            buildInputs = [ zig ];

            # https://github.com/ziglang/zig/issues/6810
            XDG_CACHE_HOME = "xdg_cache";

            zigFlags = [ "-Doptimize=${optimize}" ];

            buildPhase = ''
              runHook preBuild
              zig build $zigFlags
              runHook postBuild
            '';

            doCheck = true;
            checkPhase = ''
              runHook preCheck
              zig build test $zigFlags
              runHook postCheck
            '';

            installPhase = ''
              runHook preInstall
              zig build install --prefix $out $zigFlags
              runHook postInstall
            '';
          };
      });
}