{
  inputs = {
    nixpkgs.url = "github:nixos/nixpkgs/nixos-25.11";
    flake-utils.url = "github:numtide/flake-utils";
  };

  outputs = { self, nixpkgs, flake-utils, }:
    flake-utils.lib.eachDefaultSystem (system:
      let pkgs = import nixpkgs { inherit system; };
      in {
        default = pkgs.mkShell {
          packages = [
            pkgs.nodejs
            pkgs.yarn
          ];

          nativeBuildInputs = [ pkgs.yarnConfigHook ];

          # Must be named this for pkgs.yarnConfigHook
          yarnOfflineCache = pkgs.fetchYarnDeps {
            yarnLock = ./yarn.lock;
          };

          # PLAYWRIGHT_BROWSERS_PATH = pkgs.playwright-driver.browsers;
          # PLAYWRIGHT_SKIP_BROWSER_DOWNLOAD = "1";

          # Optional but often needed in Nix sandboxes:
          # XDG_CACHE_HOME = "$TMPDIR/xdg-cache";
          # XDG_CONFIG_HOME = "$TMPDIR/xdg-config";
          # XDG_DATA_HOME = "$TMPDIR/xdg-data";
        };
      }
    );
}