{
  description = "OCaml -> JavaScript demo using js_of_ocaml";

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

  outputs =
    { self, nixpkgs }:
    let
      system = "x86_64-linux";
      pkgs = import nixpkgs { inherit system; };
    in
    {
      devShells.${system}.default = pkgs.mkShell {
        packages = with pkgs; [
          ocaml
          dune_3
          ocamlPackages.js_of_ocaml
          ocamlPackages.js_of_ocaml-compiler
          nodejs
          tmux
          ocamlPackages.ocaml-lsp
          ocamlPackages.ocamlformat
          (pkgs.writeShellApplication {
            name = "dev";
            runtimeInputs = [ dune nodejs tmux ];
            text = ''
              SESSION=ocaml-js

              tmux new-session -d -s "$SESSION"

              tmux new-window -t "$SESSION" -n build
              tmux send-keys -t "$SESSION:0" "dune build main.bc.js --watch" C-m

              tmux new-window -t "$SESSION" -n server
              tmux send-keys -t "$SESSION:1" "npx live-server result" C-m

              tmux attach -t "$SESSION"
            '';
          })
        ];
        shellHook = ''
          echo "Run 'dev' to start tmux dev environment."
        '';
      };

      packages.${system}.default = pkgs.stdenv.mkDerivation {
        pname = "ocaml-js-demo";
        version = "0.1";

        src = ./.;

        nativeBuildInputs = with pkgs; [
          ocaml
          dune_3
          ocamlPackages.js_of_ocaml
          ocamlPackages.js_of_ocaml-compiler
          ocamlPackages.js_of_ocaml-ppx
        ];

        buildPhase = ''
          dune build main.bc.js
        '';

        installPhase = ''
          mkdir -p $out
          cp _build/default/main.bc.js $out/
          cp index.html $out/
        '';
      };
    };
}