{
  description = "NixOS configuration";

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

    # home-manager, used for managing user configuration
    home-manager = {
      url = "github:nix-community/home-manager/master";
      # The `follows` keyword in inputs is used for inheritance.
      # Here, `inputs.nixpkgs` of home-manager is kept consistent with
      # the `inputs.nixpkgs` of the current flake,
      # to avoid problems caused by different versions of nixpkgs.
      inputs.nixpkgs.follows = "nixpkgs";
    };

    silentSDDM = {
      url = "github:uiriansan/SilentSDDM";
      inputs.nixpkgs.follows = "nixpkgs";
    };

    nixcats.url = "github:BirdeeHub/nixCats-nvim";

    hyprland-git = {
      url = "github:hyprwm/Hyprland/25250527793eb04bb60f103abe7f06370b9f6e1c";
      inputs.nixpkgs.follows = "nixpkgs";
    };
  };

  outputs = inputs @ {
    nixpkgs,
    home-manager,
    silentSDDM,
    ...
  }: {
    nixosConfigurations = {
      girlCore = nixpkgs.lib.nixosSystem {
        specialArgs = {inherit inputs;};
        modules = [
          ./configuration.nix
          # make home-manager as a module of nixos
          # so that home-manager configuration will be deployed automatically when executing `nixos-rebuild switch`
          home-manager.nixosModules.home-manager
          silentSDDM.nixosModules.default
        ];
      };
    };
  };
}