diff --git a/CMakeLists.txt b/CMakeLists.txt
index 94298ec..8b01464 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -67,13 +67,17 @@ endif()
 if(BUILD_TESTS)
 	enable_testing()
 
-	include(FetchContent)
-	FetchContent_Declare(
-		googletest
-		URL https://github.com/google/googletest/archive/refs/tags/v1.15.2.zip
-	)
-	set(gtest_force_shared_crt ON CACHE BOOL "" FORCE)
-	FetchContent_MakeAvailable(googletest)
+	find_package(GTest QUIET)
+
+	if(NOT GTest_FOUND)
+		include(FetchContent)
+		FetchContent_Declare(
+			googletest
+			URL https://github.com/google/googletest/archive/refs/tags/v1.15.2.zip
+		)
+		set(gtest_force_shared_crt ON CACHE BOOL "" FORCE)
+		FetchContent_MakeAvailable(googletest)
+	endif()
 
 	file(GLOB TEST_SOURCES "${CMAKE_SOURCE_DIR}/tests/*.cpp")
 
@@ -86,3 +90,4 @@ if(BUILD_TESTS)
 	include(GoogleTest)
 	gtest_discover_tests(smath_tests)
 endif()
+
diff --git a/README.md b/README.md
index 4fb4c30..26a45ea 100644
--- a/README.md
+++ b/README.md
@@ -1,4 +1,19 @@
 # smath
 
-Single-file linear algebra math library for C++23.
+Single-file, header-only linear algebra math library for C++23.
+
+## Features
+
+- Generic `Vec<N, T>` class with useful aliases `Vec2/Vec3/Vec4` and friendly accessors (`x/y/z/w`, `r/g/b/a`). They support approx-equal and tuple/structured bindings.
+- `std::format` support.
+- Compile-time swizzles via `swizzle<"...">`.
+- Generic matrix `Mat` class with useful aliases `Mat2/Mat3/Mat4`.
+- `Quaternion<T>` built on `Vec4`.
+- Angle helpers `rad/deg/turns` respecting a configurable base unit via the macro `SMATH_ANGLE_UNIT`.
+- Optional implicit conversions.
+- Packing utilities for normalized RGBA (`pack_unorm4x8`, `unpack_snorm4x8`, etc.).
+
+## License
+
+This library is licensed under the Apache License 2.0. See the (LICENSE.txt)[LICENSE.txt] file for more details.
 
diff --git a/flake.nix b/flake.nix
index ce4b778..3126772 100644
--- a/flake.nix
+++ b/flake.nix
@@ -36,7 +36,11 @@
 
           src = ./.;
 
-          nativeBuildInputs = [ pkgs.copyPkgconfigItems ];
+          nativeBuildInputs = with pkgs; [
+            cmake
+            gtest
+            copyPkgconfigItems
+          ];
 
           pkgconfigItems = [
             (pkgs.makePkgconfigItem rec {
@@ -51,17 +55,18 @@
             })
           ];
 
-          dontBuild = true;
-
           installPhase = ''
             runHook preInstall
             mkdir -p $out/include
-            cp include/*.hpp $out/include/
+            cp ../include/smath.hpp $out/include/
             runHook postInstall
           '';
 
+          dontBuild = false;
+          doCheck = true;
+
           meta = with pkgs.lib; {
-            description = desc;
+            description = "Single-file linear algebra math library for C++23.";
             homepage = "https://github.com/slendidev/smath";
             license = licenses.asl20;
             platforms = platforms.all;