{
  description = "chess_interface Development Environment";

  inputs = {
    nixpkgs.url = "github:nixos/nixpkgs/nixpkgs-unstable";
    zig-overlay.url = "github:mitchellh/zig-overlay";
    zig-overlay.inputs.nixpkgs.follows = "nixpkgs";
    flake-utils.url = "github:numtide/flake-utils";
  };

  outputs = { self, nixpkgs, zig-overlay, flake-utils, ... }:
    flake-utils.lib.eachDefaultSystem (system:
      let
        pkgs = import nixpkgs {
          inherit system;
          overlays = [
            zig-overlay.overlays.default   # <-- use the flake overlay, NOT (import zig-overlay)
          ];
        };
      in {
        devShells.default = pkgs.mkShell {
          packages = with pkgs; [
            zigpkgs.master   # Zig nightly (“master”)
            zls              # Zig LSP (optional)
          ];

          ZIG_GLOBAL_CACHE_DIR = ".zig-cache-global";

          shellHook = ''
            echo "Welcome to the chess_interface dev env (${system})"
            echo "Zig: $(zig version)"
          '';
        };
      });
}