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

  outputs = { self, nixpkgs, flake-utils }: flake-utils.lib.eachDefaultSystem (system:
    let
      pkgs = import nixpkgs { inherit system; };
    in
    {
      packages = rec {
        u01 = pkgs.callPackage
          ({ stdenv, catch2_3, cmake }: stdenv.mkDerivation {
            name = "ecg-u01";

            src = ./u01;

            nativeBuildInputs = [ catch2_3 cmake ];

            doCheck = true;
          })
          { };

        u02 = pkgs.callPackage
          ({ stdenv, catch2_3, cmake, freeglut, libGL, libGLU }: stdenv.mkDerivation {
            name = "ecg-u02";

            src = ./u02;

            nativeBuildInputs = [ catch2_3 cmake freeglut libGL libGLU ];

            doCheck = true;
          })
          { };
      };

      devShells.default = pkgs.mkShell {
        nativeBuildInputs = with pkgs; [ catch2_3 cmake freeglut libGL libGLU ];
      };
    });
}