{
  inputs = {
    nixpkgs.url = "nixpkgs/nixpkgs-unstable";
  };
  outputs = {nixpkgs, ...}: let
    system = "x86_64-linux";
    pkgs = nixpkgs.legacyPackages.${system};
    debugGhcOptions = pkgs.lib.concatStringsSep " " (debugGhcFlags ++ commonGhcFlags);
    debugGhcFlags = [
      "-O0"
      "-Wall"
      "-Widentities"
      "-Wincomplete-record-updates"
      "-Wincomplete-uni-patterns"
      # "-Wmissing-export-lists"
      "-Wmissing-home-modules"
      "-Wpartial-fields"
      "-Wredundant-constraints"
      "-threaded"
      "-rtsopts"
      "-with-rtsopts=-N"
      "-main-is Game"
    ];
    haddockOptions = pkgs.lib.concatStringsSep " " haddockFlags;
    haddockFlags = [
      "--html"
      "--odir docs"
      "--optghc=-i./src"
      "src/Game.hs"
    ];
    releaseGhcOptions = pkgs.lib.concatStringsSep " " (releaseGhcFlags ++ commonGhcFlags);
    releaseGhcFlags = [
      "-O2"
      "-threaded"
      "-rtsopts"
      "-with-rtsopts=-N"
      "-main-is Game"
    ];
    noHaddockOptions = "";
    commonGhcFlags = [
      "-i./src"
    ];
    ghcPackages = p: [
      p.GLFW-b
      p.linear
      p.OpenGL
    ];
  in {
    packages.${system} = {
      debug = pkgs.callPackage ./package.nix {
        ghcOptions = debugGhcOptions;
        haddockOptions = noHaddockOptions;
        inherit ghcPackages;
      };
      release = pkgs.callPackage ./package.nix {
        ghcOptions = releaseGhcOptions;
        haddockOptions = noHaddockOptions;
        inherit ghcPackages;
      };
      docs = pkgs.callPackage ./package.nix {
        ghcOptions = "--version";
        inherit haddockOptions;
        inherit ghcPackages;
      };
      default = pkgs.callPackage ./package.nix {
        ghcOptions = releaseGhcOptions;
        inherit haddockOptions;
        inherit ghcPackages;
      };
    };
  };
}