diff --git a/include/uui/config.hpp b/include/uui/config.hpp
new file mode 100644
index 0000000..1afb3a0
--- /dev/null
+++ b/include/uui/config.hpp
@@ -0,0 +1,8 @@
+#pragma once
+
+#include "graphic_context.hpp"
+
+namespace Config
+{
+constexpr unsigned int FONT_TEXTURE_UNIT = GL_TEXTURE0;
+}
diff --git a/include/uui/opengl/component.hpp b/include/uui/opengl/component.hpp
index 1f44a39..b2c57bc 100644
--- a/include/uui/opengl/component.hpp
+++ b/include/uui/opengl/component.hpp
@@ -18,7 +18,7 @@ public:
 	GlComponent(GlComponent&&) = delete;
 	~GlComponent();
 
-	void set_background_color(float r, float g, float b, float a = 0.0f);
+	void set_background_color(float r, float g, float b, float a = 1.0f);
 
 protected:
 	std::shared_ptr<GlWindow> window;
diff --git a/manifest.md b/manifest.md
new file mode 100644
index 0000000..b7f40bd
--- /dev/null
+++ b/manifest.md
@@ -0,0 +1,30 @@
+# UUI : micro UI Toolkit
+
+
+* C++ + Vulkan/OpenGL
+
+* Python binding
+
+* Ease of use : safe and good semantic
+
+* Let custom rendering
+
+
+## Technical
+
+* minimum ressource : CPU/memory
+
+* minimum redraw
+
+* core profile : no immediate mode
+
+* Object based
+
+* Init/Render lambda
+
+* Opengl context
+
+
+## Layout / Style
+
+* Constraint based? padding/margin?
diff --git a/src/test/example_gl.cpp b/src/test/example_gl.cpp
index 8f82bb9..f1eeb8b 100644
--- a/src/test/example_gl.cpp
+++ b/src/test/example_gl.cpp
@@ -15,10 +15,12 @@ int main()
 			uui::GlApplication app;
 			// uui::GlApplication app2; // exception : application already created
 			auto window = app.create_window(800, 600, "OpenGl!");
-			// auto comp = window->create_component(0, 100, 0.5f, 50);
-			// comp->set_background_color(0.8f, 0.1f, 0.5f);
+			auto comp = window->create_component(0, 100, 0.5f, 50);
+			comp->set_background_color(0.8f, 0.1f, 0.5f);
+			comp = window->create_component(0.25f, 50, 0.4f, 150);
+			comp->set_background_color(0.3f, 0.8f, 0.4f, 0.5f);
 			auto label = window->create_label(50, 50, "Hello World!", {0.5f, 1.0f, 0.5f, 1.0f});
-			label->set_background_color(0.1f, 0.2f, 0.5f);
+			label->set_background_color(0.1f, 0.2f, 0.5f, 0.8f);
 			label = window->create_label(0.5f, 0.5f, "Hello World!", {1.0f, 1.0f, 1.0f, 0.5f});
 			label->set_background_color(0.5f, 0.5f, 0.1f);
 			label = window->create_label(0.75f, 0.75f, "Hello World!", {1.0f, 1.0f, 1.0f, 0.1f});
@@ -32,9 +34,12 @@ int main()
 		// 	comp->set_background_color(0.8f, 0.1f, 0.5f);
 		// 	comp = window_1->create_component(0.75f, 0.75f, 0.25f, 0.25f);
 		// 	comp->set_background_color(0.2f, 0.1f, 0.5f);
+
 		// 	auto window_2 = app.create_window(600, 600, "OpenGL 2!");
 		// 	comp = window_2->create_component(0, 0.5f, 100, 0.5f);
 		// 	comp->set_background_color(0.2f, 0.5f, 0.3f);
+		// 	auto label = window_2->create_label(50, 50, "Hello World!", {0.5f, 1.0f, 0.5f, 1.0f});
+		// 	label->set_background_color(0.1f, 0.2f, 0.5f);
 		// 	app.run();
 		// }
 	}
diff --git a/src/uui/opengl/component.cpp b/src/uui/opengl/component.cpp
index 922c016..1a43e76 100644
--- a/src/uui/opengl/component.cpp
+++ b/src/uui/opengl/component.cpp
@@ -40,7 +40,7 @@ uui::GlComponent::~GlComponent()
 		deinit();
 }
 
-void uui::GlComponent::set_background_color(float r, float g, float b, float a)
+void uui::GlComponent::set_background_color(float r, float g, float b, float a /*=0.0f*/)
 {
 	background_color = {r, g, b, a};
 	glBindVertexArray(gl_vao);
@@ -95,12 +95,14 @@ void uui::GlComponent::set_vbo_data()
 	float x_max = x_min + (2.0f * vert_w);
 	float y_min = (-2.0f * vert_y) + 1.0f;
 	float y_max = y_min - (2.0f * vert_h);
+	std::cout << "Sending vbo data with color: " << background_color[0] << ", " << background_color[1] << ", " << background_color[2] << ", "
+				 << background_color[3] << std::endl;
 	// clang-format off
 	float vertices[] = {
-		x_max, y_min, 0.0f, background_color[0] , background_color[1], background_color[2], background_color[3], // top right
-		x_max, y_max, 0.0f, background_color[0] , background_color[1], background_color[2], background_color[3], // bottom right
-		x_min, y_max, 0.0f, background_color[0] , background_color[1], background_color[2], background_color[3], // bottom left
-		x_min, y_min, 0.0f, background_color[0] , background_color[1], background_color[2], background_color[3]  // top left
+		x_max, y_min, background_color[0] , background_color[1], background_color[2], background_color[3], // top right
+		x_max, y_max, background_color[0] , background_color[1], background_color[2], background_color[3], // bottom right
+		x_min, y_max, background_color[0] , background_color[1], background_color[2], background_color[3], // bottom left
+		x_min, y_min, background_color[0] , background_color[1], background_color[2], background_color[3]  // top left
 	};
 	// clang-format on
 	glBindBuffer(GL_ARRAY_BUFFER, gl_vbo);
@@ -108,20 +110,20 @@ void uui::GlComponent::set_vbo_data()
 
 	glVertexAttribPointer(
 		 0, // index
-		 3, // size
+		 2, // size
 		 GL_FLOAT, // type
 		 GL_FALSE, // enable normalization,
-		 7 * sizeof(float), // stride
+		 6 * sizeof(float), // stride
 		 (void*)0 // offset
 	);
 	glEnableVertexAttribArray(0);
 	glVertexAttribPointer(
 		 1, // index
-		 3, // size
+		 4, // size
 		 GL_FLOAT, // type
 		 GL_FALSE, // enable normalization,
-		 7 * sizeof(float), // stride
-		 (void*)(3 * sizeof(float)) // offset
+		 6 * sizeof(float), // stride
+		 (void*)(2 * sizeof(float)) // offset
 	);
 	glEnableVertexAttribArray(1);
 }
diff --git a/src/uui/opengl/font_manager.cpp b/src/uui/opengl/font_manager.cpp
index ec1b478..546ae6e 100644
--- a/src/uui/opengl/font_manager.cpp
+++ b/src/uui/opengl/font_manager.cpp
@@ -6,6 +6,7 @@
 #include <algorithm>
 #include <iostream>
 
+#include "uui/config.hpp"
 #include "uui/opengl/application.hpp"
 #include "uui/opengl/gl_utils.hpp"
 #include "uui/shader.hpp"
@@ -166,7 +167,7 @@ const uui::GlFontManager::Font& uui::GlFontManager::init_font(const std::string&
 	glLinkProgram(gl_program);
 
 	// Create a texture that will be used to hold all ASCII glyphs
-	glActiveTexture(GL_TEXTURE0);
+	glActiveTexture(Config::FONT_TEXTURE_UNIT);
 	glGenTextures(1, &font.atlas_texture);
 	glBindTexture(GL_TEXTURE_2D, font.atlas_texture);
 
@@ -249,7 +250,7 @@ void uui::GlFontManager::render_text(
 	glGetIntegerv(GL_CURRENT_PROGRAM, (GLint*)(&gl_prev_program));
 	glUseProgram(gl_program);
 
-	glActiveTexture(GL_TEXTURE0);
+	glActiveTexture(Config::FONT_TEXTURE_UNIT);
 	auto [color_r, color_g, color_b, color_a] = text_color;
 	glUniform4f(glGetUniformLocation(gl_program, "textColor"), color_r, color_g, color_b, color_a);
 	glBindVertexArray(gl_vao);
diff --git a/src/uui/opengl/shaders/main.frag b/src/uui/opengl/shaders/main.frag
index 58aeffd..7dca716 100644
--- a/src/uui/opengl/shaders/main.frag
+++ b/src/uui/opengl/shaders/main.frag
@@ -7,4 +7,5 @@ in vec4 backgroundColor;
 void main()
 {
 	FragColor = backgroundColor;
+	// FragColor = vec4(backgroundColor.xyz * backgroundColor.a, backgroundColor.a); // premultiply
 }
diff --git a/src/uui/opengl/window.cpp b/src/uui/opengl/window.cpp
index eb4618c..d728d77 100644
--- a/src/uui/opengl/window.cpp
+++ b/src/uui/opengl/window.cpp
@@ -120,7 +120,8 @@ void uui::GlWindow::init()
 
 	// glEnable(GL_CULL_FACE);
 	glEnable(GL_BLEND);
-	glBlendFunc(GL_SRC_ALPHA, GL_DST_ALPHA);
+	glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
+	glBlendEquation(GL_FUNC_ADD);
 
 	if constexpr(uui::GlApplication::debug_mode)
 	{