Update README.md

README.md

@@ -3,14 +3,49 @@ a small C++ game framework for 2D games.
 
 this will likely see breaking changes.
 
-#### Prerequisites 
+#### prerequisites 
  - A C++17 compiler and CMake
  - Only an SDL2 `platform` [is done](https://github.com/NoelFB/blah/blob/master/private/blah/internal/platform_sdl2.cpp). CMake will need to find SDL2 via `SDL2_INCLUDE_DIRS` and `SDL2_LIBRARIES`
  - Only an OpenGL `graphics` [is done](https://github.com/NoelFB/blah/blob/master/private/blah/internal/graphics_opengl.cpp), so it currently requires OpenGL.
  
-#### Notes
+#### notes
  - There are probably lots of small bugs as this is highly untested. Best used as a learning resource for now.
  - There's a custom "vector" class which is called List and Stacklist which may later be replaced with std::vector
  - There's no Shader abstraction, so the [Sprite Batcher](https://github.com/NoelFB/blah/blob/master/public/blah/drawing/batch.h) has hard-coded GLSL. This will need to change.
  - The rendering layer may be replaced with [FNA3D](https://github.com/FNA-XNA/FNA3D), [BGFX](https://github.com/bkaradzic/bgfx), [Sokol](https://github.com/floooh/sokol), or something else.
  - There's no Audio layer implementation yet.
+
+
+#### a sample application
+
+```cpp
+#include <blah.h>
+using namespace Blah;
+
+Batch batch;
+
+void render()
+{
+	Graphics::clear(Graphics::backbuffer, 0x00000000);
+	
+	batch.push_matrix(Mat3x2::create_transform(Vec2(App::draw_width(), App::draw_height()) / 2, Vec2::zero, Vec2::one, Time::elapsed * Calc::TAU));
+	batch.rect(Rect(-32, -32, 64, 64), 0xff0000);
+	batch.pop_matrix();
+	
+	batch.render(Graphics::backbuffer);
+	batch.clear();
+}
+
+int main()
+{
+	Config config;
+	config.name = "blah app";
+	config.width = 1280;
+	config.height = 720;
+	config.on_render = render;
+	
+	App::run(&config);
+	return 0;
+}
+
+```