Need nix help please

Code Help Nix
1

Question: why can’t I get my box file to cooperate haha help me

Repl link:

https://replit.com/@Forrestey/Fresh?s=app

{lib, buildPackages, ... }:

let
  # Define Node.js version and packages
  nodejsVersion = "14.x";
  nodejs = buildPackages.nodejs.override { version = nodejsVersion; };

  # Define Python version and packages (if needed)
  pythonVersion = "3.8";
  pythonPackages = buildPackages.python38;

  # Define the mapping library (easiest option: Leaflet.js)
  mappingLibrary = lib.mkIf true (buildPackages.leaflet);

  # Define the preferred database (easiest option: MongoDB)
  database = lib.mkIf true (buildPackages.mongodb);
in {
  # Environment variables
  environment.systemPackages = with lib; [
    # General tools
    git
    curl
    wget

    # Node.js and npm
    (nodejs.withPackages (nodePackages: with nodePackages; [
      # Add any npm packages you need here
    ]))

    # Python (optional - if you're using Python)
    (pythonPackages.withPackages (pythonPackages: with pythonPackages; [
      # Add any Python packages you need here
    ]))
    
    # Mapping Library (easiest: Leaflet.js)
    mappingLibrary

    # Database (easiest: MongoDB)
    database
  ];

  # Replit specific configurations
  Replit = {
    languageVersion = "javascript";
    runCommand = "npm install && npm start";
  };
}