{
  description = "The Sieve of Eratosthenes implemented in many different languages";

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

  outputs = { self, nixpkgs, flake-utils, ... }:
    flake-utils.lib.eachDefaultSystem (system:
      let
        pkgs = nixpkgs.legacyPackages.${system};
        inherit (pkgs) lib;

        # Check if project has a shell.nix
        hasShell = dir: (builtins.readDir ./${dir}) ? "shell.nix";

        # Get all project directories
        currentDir = builtins.readDir ./.;
        dirs = lib.filterAttrs (_: v: v == "directory") currentDir;
      in
        lib.concatMapAttrs (dir: _: {
          packages.${dir} = pkgs.callPackage ./${dir} {};
        } // lib.optionalAttrs (hasShell dir) {
          devShells.${dir} = pkgs.callPackage ./${dir}/shell.nix {};
        }) dirs
    );
}