{
  description = "whc NixOS — desktop (i7-12700F + RTX 4060) + laptop (Ultra 9 285H / Arc)";

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

  outputs =
    { self, nixpkgs, ... }:
    let
      system = "x86_64-linux";
      mkSystem = host: nixpkgs.lib.nixosSystem {
        inherit system;
        modules = [ (./hosts + "/${host}") ];
      };
    in
    {
      nixosConfigurations = {
        desktop = mkSystem "desktop";
        laptop = mkSystem "laptop";
        # hostname 仍是 nixos：让不带 attr 的 `nixos-rebuild --flake .#` 也能命中
        nixos = mkSystem "laptop";
      };

      # 无 flake 时也可：把本仓库拷到 /etc/nixos 后 nixos-rebuild switch
      formatter.${system} = nixpkgs.legacyPackages.${system}.nixfmt-rfc-style;
    };
}