{
  # Den adapted from default microvm template.
  description = "NixOS in MicroVMs with Den";

  nixConfig = {
    extra-substituters = [ "https://microvm.cachix.org" ];
    extra-trusted-public-keys = [ "microvm.cachix.org-1:oXnBc6hRE3eX5rSYdRyMYXnfzcCxC7yKPTbZXALsqys=" ];
  };

  inputs.den.url = "github:vic/den";
  inputs.flake-aspects.url = "github:vic/flake-aspects";
  inputs.import-tree.url = "github:vic/import-tree";

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

  inputs.microvm = {
    url = "github:microvm-nix/microvm.nix";
    inputs.nixpkgs.follows = "nixpkgs";
  };

  outputs =
    inputs:
    (inputs.nixpkgs.lib.evalModules {
      modules = [ (inputs.import-tree ./modules) ];
      specialArgs = { inherit inputs; };
    }).config.flake;
}