{
  description = "NixOS System Configuration for duckland.org";

  # Binary cache configuration for faster builds
  nixConfig = {
    allowUnfree = true;
    # Binary cache servers (substituters)
    extra-substituters = [
      "https://cache.nixos.org"
      "https://chaotic-nyx.cachix.org"
      "https://nix-community.cachix.org"
    ];
    # Public keys for binary cache verification
    extra-trusted-public-keys = [
      "cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY="
      "chaotic-nyx.cachix.org-1:HfnXSw4pj95iI/n17rIDy40agHj12WfF+Gqk6SonIT8="
      "nix-community.cachix.org-1:mB9FSh9qf2dCimDSUo8Zy7bkq5CX+/rkCWyvRCYg3Fs="
    ];
  };

  inputs = {
    nixpkgs.url = "github:nixos/nixpkgs/nixos-unstable";
    # nixpkgs.url = "github:nixos/nixpkgs/nixos-25.05";
    nixpkgs-stable.url = "github:nixos/nixpkgs/nixos-25.05";
    # disko.inputs.nixpkgs.follows = "nixpkgs";
    # disko.url = "github:nix-community/disko";
    # nixos-cosmic.inputs.nixpkgs.follows = "nixpkgs";
    # nixos-cosmic.url = "github:lilyinstarlight/nixos-cosmic";
    bzmenu.url = "github:e-tho/bzmenu";
    catppuccin.url = "github:catppuccin/nix";
    colmena.url = "github:zhaofengli/colmena";
    colmena.inputs.nixpkgs.follows = "nixpkgs";
    home-manager.url = "github:nix-community/home-manager";
    home-manager.inputs.nixpkgs.follows = "nixpkgs";
    naviterm.url = "gitlab:detoxify92/naviterm";
    nixos-hardware.url = "github:NixOS/nixos-hardware/master";
    nvf.url = "github:notashelf/nvf";
    nvf.inputs.nixpkgs.follows = "nixpkgs";
  };

  outputs = inputs @ {
    self,
    nixpkgs,
    nix,
    nixpkgs-stable,
    nixos-hardware,
    home-manager,
    catppuccin,
    colmena,
    ...
  }: let
    inherit (self) outputs;
    lib = nixpkgs.lib // home-manager.lib;
  in {
    inherit lib;
    nixpkgs.config.allowUnfree = true;
    config.allowUnfree = true;
    nixpkgs.config.allowUnfreePredicate = pkg:
      builtins.elem (lib.getName pkg) ["widevine-cdm"];
    colmena = {
      meta = {
        nixpkgs = import nixpkgs {system = "x86_64-linux";};
        specialArgs = {inherit inputs outputs;};
      };
      # ace = import ./hosts/ace/colmena.nix;          # Acer C720
      book = import ./hosts/book/colmena.nix; # Google Pixelbook 2017 w/ nvme.
      display = import ./hosts/display/colmena.nix; # Pi4
      # eve = import ./hosts/eve/colmena.nix; # Google Pixelbook 2017 w/ eMMC.
      fred = import ./hosts/fred/colmena.nix; # acer server
      loki = import ./hosts/loki/colmena.nix; # Dell XPS 13
      # pi1 = import ./hosts/pi1/colmena.nix;
      # pocket2 = import ./hosts/pocket2/colmena.nix;
      smaug = import ./hosts/smaug/colmena.nix; # Thinkpad x260
      w1 = import ./hosts/w1/colmena.nix; # Hetzner VPS
      # w2 = import ./hosts/w2/colmena.nix;
    };

    nixosConfigurations = {
      # clients
      ace = lib.nixosSystem {
        modules = [./hosts/ace];
        specialArgs = {inherit inputs outputs;};
      };
      dragon = lib.nixosSystem {
        modules = [./hosts/dragon];
        specialArgs = {inherit inputs outputs;};
      };
      eve = lib.nixosSystem {
        modules = [./hosts/eve];
        specialArgs = {inherit inputs outputs;};
      };
      loki = lib.nixosSystem {
        modules = [./hosts/loki];
        specialArgs = {inherit inputs outputs;};
      };

      pocket2 = lib.nixosSystem {
        modules = [./hosts/pocket2];
        specialArgs = {inherit inputs outputs;};
      };
      smaug = lib.nixosSystem {
        modules = [./hosts/smaug];
        specialArgs = {inherit inputs outputs;};
      };
      t2 = lib.nixosSystem {
        modules = [./hosts/t2];
        specialArgs = {inherit inputs outputs;};
      };
      pi1 = lib.nixosSystem {
        modules = [./hosts/pi1];
        specialArgs = {inherit inputs outputs;};
      };

      # servers
      display = lib.nixosSystem {
        modules = [./hosts/display];
        specialArgs = {inherit inputs outputs;};
      };
      fred = lib.nixosSystem {
        modules = [./hosts/fred];
        specialArgs = {inherit inputs outputs;};
      };
      vm = lib.nixosSystem {
        modules = [
          "${nixpkgs}/nixos/modules/installer/cd-dvd/installation-cd-graphical-gnome.nix"
          "${nixpkgs}/nixos/modules/installer/cd-dvd/channel.nix"
          ./hosts/vm
        ];
        specialArgs = {inherit inputs outputs;};
      };
      harper2 = lib.nixosSystem {
        modules = [./hosts/harper2];
        specialArgs = {inherit inputs outputs;};
      };
      harper = lib.nixosSystem {
        modules = [./hosts/harper];
        specialArgs = {inherit inputs outputs;};
      };
      nuwww = lib.nixosSystem {
        modules = [./hosts/nuwww];
        specialArgs = {inherit inputs outputs;};
      };
      pihole = lib.nixosSystem {
        modules = [./hosts/pihole];
        specialArgs = {inherit inputs outputs;};
      };
      www2 = lib.nixosSystem {
        modules = [./hosts/www2];
        specialArgs = {inherit inputs outputs;};
      };
      w1 = lib.nixosSystem {
        modules = [./hosts/w1];
        specialArgs = {inherit inputs outputs;};
      };
      # w2 = lib.nixosSystem {
      #   modules = [./hosts/w2];
      #   specialArgs = {
      #     inherit inputs outputs;
      #   };
      # };
    };
  };
}