adding default.nix for nix packaging

default.nix

@@ -0,0 +1,48 @@
+{ lib
+, stdenv
+, fetchFromGitHub
+, meson
+, ninja
+, pkg-config
+, wrapGAppsHook4
+, gtk4
+, gtkmm4
+, libsigcxx
+}:
+
+stdenv.mkDerivation rec {
+  pname = "minesweeper";
+  version = "0.2.0";
+
+  src = ./.;
+  
+  # If you want to use fetchFromGitHub instead:
+  # src = fetchFromGitHub {
+  #   owner = "username";
+  #   repo = "minesweeper";
+  #   rev = "v${version}";
+  #   hash = "sha256-0000000000000000000000000000000000000000000=";
+  # };
+
+  nativeBuildInputs = [
+    meson
+    ninja
+    pkg-config
+    wrapGAppsHook4
+  ];
+
+  buildInputs = [
+    gtk4
+    gtkmm4
+    libsigcxx
+  ];
+
+  meta = with lib; {
+    description = "Modern Minesweeper game with GTK4 interface";
+    homepage = "https://github.com/username/minesweeper";
+    license = licenses.mit;
+    platforms = platforms.linux;
+    maintainers = with maintainers; [ /* your name here */ ];
+    mainProgram = "minesweeper";
+  };
+}