diff --git a/CMakeLists.txt b/CMakeLists.txt
index dd327d6..effda97 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -21,4 +21,4 @@ set(CMAKE_CXX_STANDARD_REQUIRED ON)
 set(CMAKE_CXX_EXTENSIONS OFF)
 
 add_subdirectory(src)
-add_subdirectory(examples/simple)
\ No newline at end of file
+add_subdirectory(examples)
\ No newline at end of file
diff --git a/examples/CMakeLists.txt b/examples/CMakeLists.txt
new file mode 100644
index 0000000..2bdd295
--- /dev/null
+++ b/examples/CMakeLists.txt
@@ -0,0 +1,2 @@
+add_subdirectory(simple)
+add_subdirectory(pong)
\ No newline at end of file
diff --git a/examples/pong/CMakeLists.txt b/examples/pong/CMakeLists.txt
new file mode 100644
index 0000000..cbdcc48
--- /dev/null
+++ b/examples/pong/CMakeLists.txt
@@ -0,0 +1,4 @@
+
+add_executable(paradiso_pong pong.cpp)
+
+target_link_libraries(paradiso_pong paradiso_core)
\ No newline at end of file
diff --git a/examples/pong/pong.cpp b/examples/pong/pong.cpp
new file mode 100644
index 0000000..1643d92
--- /dev/null
+++ b/examples/pong/pong.cpp
@@ -0,0 +1,259 @@
+/**
+ * paradiso - Paradigmen der Softwareentwicklung
+ *
+ * (c) Copyright 2023 Hartmut Seichter
+ *
+ */
+
+#include <paradiso/bitmap.hpp>
+#include <paradiso/context.hpp>
+#include <paradiso/geometry.hpp>
+#include <paradiso/renderer.hpp>
+#include <paradiso/shader.hpp>
+#include <paradiso/sprite.hpp>
+#include <paradiso/vector.hpp>
+#include <paradiso/window.hpp>
+
+#include <unordered_map>
+
+#include <iomanip>
+#include <iostream>
+
+struct PongStage {
+
+    using Vec2 = paradiso::Vector2<float>;
+
+    Vec2 tl{Vec2::make(-1.0f, -1.0f)};
+    Vec2 br{Vec2::make(+1.0f, +1.0f)};
+
+    enum class TouchPoint { None, Left, Right, Bottom, Top };
+
+    TouchPoint touch(const Vec2& o, float eps = 0.001f) noexcept {
+        std::unordered_map<TouchPoint, float> deltas;
+        deltas[TouchPoint::Left] = std::abs(o.x() - tl.x());
+        deltas[TouchPoint::Right] = std::abs(o.x() - br.x());
+        deltas[TouchPoint::Bottom] = std::abs(o.y() - br.y());
+        deltas[TouchPoint::Top] = std::abs(o.y() - tl.y());
+
+        auto min_el = *std::min_element(
+            std::begin(deltas), std::end(deltas),
+            [](const auto& l, const auto& r) { return l.second < r.second; });
+
+        auto t = (min_el.second <= eps) ? min_el.first : TouchPoint::None;
+
+        if (t != TouchPoint::None) {
+            sprite.bitmap.pixel(0,0) = paradiso::RGBA::white();
+        } else {
+            sprite.bitmap.pixel(0,0) = paradiso::RGBA::black();
+        }
+
+        return t;
+    };
+
+    // sprite
+    paradiso::Sprite sprite{
+        .bitmap = paradiso::Bitmap::from_data(paradiso::Size{1, 1},
+                                              paradiso::RGBA::from_rgb(0x80,0xFF,0xFF))
+                                              };
+
+    void draw(const paradiso::Shader& shader) {
+        renderer.draw(sprite, shader);
+    }
+
+    paradiso::Renderer renderer{};
+};
+
+struct PongPaddle {
+
+    static constexpr float whoopiness = 0.95f;
+
+    // sprite
+    paradiso::Sprite sprite{
+        .bitmap = paradiso::Bitmap::from_data(paradiso::Size{1, 1},
+                                              paradiso::RGBA::white()),
+        .pivot = paradiso::Vector2<float>::make(0.0f, -0.9f),
+        .scale = paradiso::Vector2<float>::make(0.25f, 0.01f)};
+
+    // keyboard handler
+    void on_keyboard(const paradiso::Window::KeyboardInputStack& input) {
+
+        if (input.size()) {
+            if (input.top().key == 'A' || input.top().key == 263) {
+                velocity_horizontal -= 0.01;
+            } else if (input.top().key == 'D' || input.top().key == 262) {
+                velocity_horizontal += 0.01;
+            }
+        }
+    }
+
+    void draw(const paradiso::Shader& shader) {
+
+        // update internal state
+        velocity_horizontal *= whoopiness;
+        sprite.pivot.x() += velocity_horizontal;
+
+        std::clamp(sprite.pivot.x(), -0.5f, 0.5f);
+
+        // update shader uniforms
+        shader.set_uniform("pivot", sprite.pivot);
+        shader.set_uniform("scale", sprite.scale);
+        shader.set_uniform("rotation", sprite.rotation);
+
+        renderer.draw(sprite, shader);
+    }
+
+    float velocity_horizontal{};
+
+    paradiso::Renderer renderer{};
+};
+
+struct PongBall {
+    // sprite
+    paradiso::Sprite sprite{
+        .bitmap = paradiso::Bitmap::from_data(paradiso::Size{1, 1},
+                                              paradiso::RGBA::white()),
+        .pivot = paradiso::Vector2<float>::make(0.0f, 0.0f),
+        .scale = paradiso::Vector2<float>::make(0.0125f, 0.0125f),
+    };
+
+    void interact(PongStage& stage) {
+
+        auto touch = stage.touch(sprite.pivot);
+
+        switch (touch) {
+        case PongStage::TouchPoint::Top:
+        case PongStage::TouchPoint::Bottom:
+            velocity.y() *= -1;
+            break;
+        case PongStage::TouchPoint::Left:
+        case PongStage::TouchPoint::Right:
+            velocity.x() *= -1;
+            break;
+        default:
+            break;
+        }
+    }
+
+    // interact ball & paddle
+    void interact(const PongPaddle& paddle) {
+        const auto& ps = paddle.sprite.scale;
+        const auto& pp = paddle.sprite.pivot;
+
+        auto left_x = pp.x() - ps.x();
+        auto right_x = pp.x() + ps.x();
+
+        static constexpr float eps{0.01f};
+
+        if (sprite.pivot.x() >= left_x && sprite.pivot.x() <= right_x &&
+            std::abs(pp.y() - sprite.pivot.y()) < eps) {
+
+            velocity.y() *= -1;
+            velocity.x() += paddle.velocity_horizontal * paddle.whoopiness;
+        }
+    }
+
+    void update() { sprite.pivot += velocity; }
+
+    void draw(const paradiso::Shader& shader) {
+
+        std::clamp(sprite.pivot.x(), -0.5f, 0.5f);
+
+        // update shader uniforms
+        shader.set_uniform("pivot", sprite.pivot);
+        shader.set_uniform("scale", sprite.scale);
+        shader.set_uniform("rotation", sprite.rotation);
+
+        renderer.draw(sprite, shader);
+    }
+
+    paradiso::Vector2<float> velocity{};
+
+    paradiso::Renderer renderer{};
+
+    constexpr void push(const auto& impulse) noexcept { velocity += impulse; }
+};
+
+auto main() -> int {
+
+    // Ausgabefenster ... sieht aus als wäre es auf dem Stack
+    auto window = paradiso::Window();
+
+    // wir bauen ein Fenster ...
+    window
+        .set_size(paradiso::Size{.width = 720, .height = 720}) // ... Grösse
+        .set_position(paradiso::Point{.x = 100, .y = 100})     // ... Position
+        .set_title("PardiSO.Pong")                             // ... Titel
+        .set_visible(true); // ... und jetzt anzeigen!
+
+    // der Fenster Kontext
+    auto ctx = paradiso::Context{};
+
+    // ein Shader (Schattierungsprogramm)
+    auto shader = paradiso::Shader{};
+
+    // wir nutzen einen vorgefertigten shader
+    shader.load_preset(paradiso::Shader::Preset::Sprite);
+
+    auto paddle = PongPaddle{};
+    auto ball = PongBall{};
+    auto stage = PongStage{};
+
+    ball.push(paradiso::Vector2<float>::make(0.0001f, -0.0005f));
+
+    // ein viewport stellt die Sicht der Kamera dar, d.h. bei quadratischen
+    // Pixeln sollte hier auch eine dementsprechende Grösse eingestellt
+    // werden
+    ctx.set_viewport(paradiso::Rectangle{
+        .position = paradiso::Point{.x = 0, .y = 0},
+        .size = window.client_size()
+                    .maximal_extent() // wir wollen das
+                                      // Seitenverhältnis beibehalten
+    });
+
+    // nothing beats a classic look
+    ctx.set_clearcolor(paradiso::RGBA::from_rgb(0x00, 0x00, 0x00));
+
+    // das update führt den hier mitgegebnen Ausdruck innerhalb der internen
+    // Updates des Fensters auf. Es wird hier auch explizit ein bool gefordert
+    // damit das update auch zu jederzeit unterbrochen werden kann
+    while (window.update([&](paradiso::Window& w) -> bool {
+        auto me = window.client_size().maximal_extent();
+
+        ctx.set_viewport(paradiso::Rectangle{
+            .position = paradiso::Point{.x = 0, .y = 0},
+            .size = me // wir wollen das
+                       // Seitenverhältnis beibehalten
+        });
+
+        // hier wird das eigentliche löschen des vorherigen Inhalts ausgelöst
+        ctx.clear();
+
+        paddle.on_keyboard(w.keyboard_input());
+
+        // still here
+        bool want_close =
+            (w.keyboard_input().size() && w.keyboard_input().top().key == 'Q');
+
+        if (!w.keyboard_input().empty()) {
+            if (w.keyboard_input().top().key == 'R') {
+                ball.sprite.pivot.x() =  0.0f;
+                ball.sprite.pivot.y() =  0.9f;
+            }
+        }
+
+        ball.interact(stage);
+        ball.interact(paddle);
+
+        ball.update();
+
+        stage.draw(shader);
+        paddle.draw(shader);
+        ball.draw(shader);
+
+        // ... signalisiere ob wir weitermachen wollen ...
+        return !want_close;
+    })) {
+    };
+
+    return 0;
+}
\ No newline at end of file
diff --git a/examples/simple/CMakeLists.txt b/examples/simple/CMakeLists.txt
index 62f3f94..1cc24a7 100644
--- a/examples/simple/CMakeLists.txt
+++ b/examples/simple/CMakeLists.txt
@@ -1,16 +1,9 @@
-set(paradiso_src
-    main.cpp
-    )
 
 add_executable(
-    paradiso
-    ${paradiso_src}
+    paradiso_simple
+    simple.cpp
     )
 
-target_link_libraries(paradiso
+target_link_libraries(paradiso_simple
     paradiso_core
     )
-
-target_include_directories(paradiso 
-    PRIVATE
-    lib)
\ No newline at end of file
diff --git a/examples/simple/main.cpp b/examples/simple/simple.cpp
similarity index 60%
rename from examples/simple/main.cpp
rename to examples/simple/simple.cpp
index eb4c1c8..09db5f1 100644
--- a/examples/simple/main.cpp
+++ b/examples/simple/simple.cpp
@@ -16,66 +16,6 @@
 #include <iomanip>
 #include <iostream>
 
-void setup_shaders(paradiso::Shader& shader) {
-    const auto unlit_v = R"(
-#version 400 core
-
-layout (location = 0) in vec3 vertices;
-layout (location = 1) in vec3 normals;
-layout (location = 2) in vec2 texture_coords;
-
-// pivot der sprite
-uniform vec2 pivot = vec2( 0.0, 0.0 );
-// scale 
-uniform vec2 scale = vec2( 1.0, 1.0 );
-// rotation
-uniform float rotation = 0.2;
-
-// wir sind natuerlich in homogenenen 3D Koordinaten unterwegs
-mat4 mm = mat4(
-    vec4( scale.x, 0.0, 0.0, 0.0),
-    vec4( 0.0, scale.y, 0.0, 0.0),
-    vec4( 0.0, 0.0, 1.0, 0.0),
-    vec4( pivot, 0.0, 1.0)
-);
-
-float sir = sin(rotation);
-float cor = cos(rotation);
-
-mat4 mr = mat4(
-    vec4( cor, sir, 0.0, 0.0),
-    vec4(-sir, cor, 0.0, 0.0),
-    vec4( 0.0, 0.0, 1.0, 0.0),
-    vec4( 0.0, 0.0, 0.0, 1.0)
-    );
-
-out vec2 tex_c; // das hier reicht die texturkoordinaten durch
-
-void main() {
-    tex_c = texture_coords; // umstaendlich aber notwendig
-    gl_Position = mm * mr * vec4(vertices, 1.0); // unsere eigentliche shader position
-}
-)";
-
-    const auto unlit_f = R"(
-#version 400 core
-
-uniform sampler2D tex_color; // hier ist unsere sprite textur (bitmap)
-
-in vec2 tex_c; // da sind die texturkoordinaten wieder
-
-out vec4 frag_color; // das hier wird der output (pixelwert/fragment)
-
-void main() {
-    frag_color = texture(tex_color,tex_c);
-})";
-
-    shader.set_source(paradiso::Shader::Type::Vertex, unlit_v);
-    shader.set_source(paradiso::Shader::Type::Fragment, unlit_f);
-
-    shader.build();
-}
-
 auto main() -> int {
 
     // Ausgabefenster ... sieht aus als wäre es auf dem Stack
@@ -85,7 +25,7 @@ auto main() -> int {
     window
         .set_size(paradiso::Size{.width = 1280, .height = 720}) // ... Grösse
         .set_position(paradiso::Point{.x = 100, .y = 100})      // ... Position
-        .set_title("PardiSO")                                   // ... Titel
+        .set_title("PardiSO.Simple")                            // ... Titel
         .set_visible(true); // ... und jetzt anzeigen!
 
     // der Fenster Kontext
@@ -107,36 +47,39 @@ auto main() -> int {
     // ein Shader (Schattierungsprogramm)
     auto shader = paradiso::Shader{};
 
-    // hier werden die Shader Programme geladen, kompiliert usw.
-    setup_shaders(shader);
+    // wir nutzen einen vorgefertigten shader
+    shader.load_preset(paradiso::Shader::Preset::Sprite);
 
     // kein schönes Design: dies sind globale Variablen ...
     uint8_t slider_value = 0xFF;
     bool want_close{false};
 
-    // eine sehr rudimentäre Eingabebehandlung. Bei vorhandenen
-    // Eingaben landen diese hier. Wer sich am Design beteiligen
-    // möchte: hier gibt es viel Potential zur Verbesserung ;)
-    window.set_keyboardcallback(
-        [&](auto& w, int key, int scancode, int action, int mods) {
-            if (key == 'Q' || key == 256) // Q oder ESC beenden das Programm
+    // hier "vor-deklariert" der Input-handler für unser Demo
+    auto SimpleKeyboardHandler =
+        [&](const paradiso::Window::KeyboardInputStack& input) {
+            // ohne Input kein Handling ...
+            if (input.empty())
+                return;
+
+            if (input.top().key == 'Q' ||
+                input.top().key == 256) // Q oder ESC beenden das Programm
                 want_close = true;
-            else if (key == 'B') { // kleine Spielerei
+            else if (input.top().key == 'B') { // kleine Spielerei
                 slider_value += 10;
-            } else if (key == 'W') {
+            } else if (input.top().key == 'W') {
                 sprite.pivot.y() += 0.1f;
-            } else if (key == 'S') {
+            } else if (input.top().key == 'S') {
                 sprite.pivot.y() -= 0.1f;
-            } else if (key == 'A') {
+            } else if (input.top().key == 'A') {
                 sprite.pivot.x() -= 0.1f;
-            } else if (key == 'D') {
+            } else if (input.top().key == 'D') {
                 sprite.pivot.x() += 0.1f;
-            } else if (key == 'P') {
+            } else if (input.top().key == 'P') {
                 sprite.scale *= 0.9;
-            } else if (key == 'R') {
+            } else if (input.top().key == 'R') {
                 sprite.rotation += 0.1;
             }
-        });
+        };
 
     // das update führt den hier mitgegebnen Ausdruck innerhalb der internen
     // Updates des Fensters auf. Es wird hier auch explizit ein bool gefordert
@@ -152,11 +95,15 @@ auto main() -> int {
         // Pixeln sollte hier auch eine dementsprechende Grösse eingestellt
         // werden
         ctx.set_viewport(paradiso::Rectangle{
+            .position = paradiso::Point{.x = 0, .y = 0},
             .size =
                 w.client_size().maximal_extent() // wir wollen das
                                                  // Seitenverhältnis beibehalten
         });
 
+        // handle keyboard input ...
+        SimpleKeyboardHandler(w.keyboard_input());
+
         // hier wird das eigentliche löschen des vorherigen Inhalts ausgelöst
         ctx.clear();
 
diff --git a/src/lib/CMakeLists.txt b/src/lib/CMakeLists.txt
index 05e3c49..d437135 100644
--- a/src/lib/CMakeLists.txt
+++ b/src/lib/CMakeLists.txt
@@ -12,9 +12,11 @@ set(paradiso_srcs
     src/window.cpp
     src/renderer.cpp
     src/context.cpp
+    src/shader_sprite.hpp
     )
 
 set(paradiso_incs
+    include/paradiso/aabb.hpp
     include/paradiso/bitmap.hpp
     include/paradiso/geometry.hpp
     include/paradiso/sprite.hpp
diff --git a/src/lib/include/paradiso/aabb.hpp b/src/lib/include/paradiso/aabb.hpp
new file mode 100644
index 0000000..8a8b77a
--- /dev/null
+++ b/src/lib/include/paradiso/aabb.hpp
@@ -0,0 +1,61 @@
+/*
+ * Copyright 2023 Hartmut Seichter
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ *
+ */
+
+#ifndef PARADISO_AABB_HPP
+#define PARADISO_AABB_HPP
+
+#include <paradiso/vector.hpp>
+
+namespace paradiso {
+struct AABB final {
+
+    Vector2<float> top_left{};
+    Vector2<float> bottom_right{};
+
+    static constexpr AABB from_vertices(auto& vertices) noexcept {
+
+        Matrix<2, 2, float> min_max;
+        min_max.set_slice<2, 1>(0, 0) = vertices.front();
+        min_max.set_slice<2, 1>(1, 0) = vertices.front();
+
+        for (const auto& v : vertices) {
+            min_max(0, 0) = std::min(min_max(0, 0), v.x());
+            min_max(0, 1) = std::min(min_max(0, 1), v.y());
+            min_max(1, 0) = std::min(min_max(1, 0), v.x());
+            min_max(1, 1) = std::min(min_max(1, 1), v.y());
+        }
+
+        return {.top_left = Vector2<float>::make(min_max(0, 0), min_max(0, 1)),
+                .bottom_right =
+                    Vector2<float>::make(min_max(1, 0), min_max(1, 1))};
+    }
+
+    bool constexpr is_inside(const Vector2<float>& v) const {
+        return (v.x() >= top_left.x() && v.x() <= bottom_right.x() && 
+                v.y() >= top_left.y() && v.y() <= bottom_right.y());
+    }
+};
+
+} // namespace paradiso
+
+#endif
\ No newline at end of file
diff --git a/src/lib/include/paradiso/bitmap.hpp b/src/lib/include/paradiso/bitmap.hpp
index bcc314a..c95f861 100644
--- a/src/lib/include/paradiso/bitmap.hpp
+++ b/src/lib/include/paradiso/bitmap.hpp
@@ -60,6 +60,7 @@ struct Bitmap final {
      * @return reference to itself
      */
     constexpr auto fill(const RGBA& color) noexcept {
+        change_count++;
         std::fill(data.begin(), data.end(), color);
         return *this;
     }
@@ -71,6 +72,7 @@ struct Bitmap final {
      * @return reference to pixel data at position
      */
     constexpr RGBA& pixel(std::integral auto x, std::integral auto y) {
+        change_count++;
         return data[y * size.width + x];
     }
 
@@ -85,8 +87,14 @@ struct Bitmap final {
         return data[y * size.width + x];
     }
 
+    constexpr void force_change() noexcept
+    {
+        change_count++;
+    } 
+
     Size size{.width = 0, .height = 0}; //!< extent of bitmap
     std::vector<RGBA> data{};           //!< data storage
+    std::uint64_t change_count{};
 };
 } // namespace paradiso
 
diff --git a/src/lib/include/paradiso/matrixbase.hpp b/src/lib/include/paradiso/matrixbase.hpp
index 56d012e..5e77268 100644
--- a/src/lib/include/paradiso/matrixbase.hpp
+++ b/src/lib/include/paradiso/matrixbase.hpp
@@ -25,6 +25,7 @@
 
 #include <paradiso/globals.hpp>
 
+#include <algorithm>
 
 namespace paradiso {
 
@@ -84,7 +85,7 @@ template <typename Scalar, typename Derived> struct MatrixBase {
 
     constexpr void normalize() { *this /= this->norm(); }
 
-    static constexpr Scalar dot(const Derived& a, const Derived& b) {
+    static constexpr Scalar dot(const auto& a, const auto& b) {
         return std::inner_product(std::begin(a), std::end(a), std::begin(b),
                                   Scalar{0});
     }
@@ -111,6 +112,13 @@ template <typename Scalar, typename Derived> struct MatrixBase {
             e -= b;
     }
 
+    constexpr void operator+=(const Derived& b) {
+        std::transform((*this).begin(),(*this).end(),b.begin(),(*this).begin(),std::plus<>());
+    }
+    constexpr void operator-=(const Derived& b) {
+        std::transform((*this).begin(),(*this).end(),b.begin(),(*this).begin(),std::minus<>());
+    }
+
     constexpr const Derived operator*(const Scalar& b) const {
         Derived r(derived());
         for (auto& e : r)
diff --git a/src/lib/include/paradiso/rgba.hpp b/src/lib/include/paradiso/rgba.hpp
index 28c6987..0ab6ec4 100644
--- a/src/lib/include/paradiso/rgba.hpp
+++ b/src/lib/include/paradiso/rgba.hpp
@@ -79,6 +79,14 @@ struct RGBA final {
         pixel = (pixel & 0xFFFFFF00) | v;
         return *this;
     }
+
+    static constexpr RGBA white() noexcept {
+        return RGBA::from_rgb(0xFF, 0xFF, 0xFF);
+    }
+
+    static constexpr RGBA black() noexcept {
+        return RGBA::from_rgb(0x00, 0x00, 0x00);
+    }
 };
 } // namespace paradiso
 
diff --git a/src/lib/include/paradiso/shader.hpp b/src/lib/include/paradiso/shader.hpp
index 9382fc9..549fe7d 100644
--- a/src/lib/include/paradiso/shader.hpp
+++ b/src/lib/include/paradiso/shader.hpp
@@ -42,9 +42,13 @@ struct Shader final {
 
     enum class Type { Vertex, Fragment, Geometry, Compute };
 
+    enum class Preset { Sprite };
+
     void set_source(Type t, const std::string& c) { source_[t] = c; }
     std::string source(Type t) const { return source_.at(t); }
 
+    bool load_preset(Preset preset);
+
     bool build();
 
     bool ready() const;
@@ -54,9 +58,11 @@ struct Shader final {
     const Shader&
     set_uniform_at_location(int location,
                             float v) const; //!< sets a float in a shader
+                            
     const Shader& set_uniform_at_location(
         int location,
         uint32_t v) const; //!< sets a 32bit unsigned in a shader
+
     const Shader& set_uniform_at_location(
         int location,
         int32_t v) const; //!< sets a 32bit signed in a shader
diff --git a/src/lib/include/paradiso/window.hpp b/src/lib/include/paradiso/window.hpp
index 0b81873..6613b99 100644
--- a/src/lib/include/paradiso/window.hpp
+++ b/src/lib/include/paradiso/window.hpp
@@ -27,19 +27,24 @@
 #include <paradiso/geometry.hpp>
 
 #include <functional>
+#include <stack>
 
 namespace paradiso {
 
+struct KeyboardInput final {
+    int key{}, scancode{}, action{}, mods{};
+};
+
 struct Window final {
+
     using Size = paradiso::Size;
     using Position = paradiso::Point;
+    using KeyboardInputStack = std::stack<KeyboardInput>;
 
     using on_updatecallback_t = std::function<bool(
         Window&)>; //! update needs to return true to continue
     using on_resizecallback_t =
         std::function<void(Window&)>; //! resize is 'informal'
-    using on_keyboardcallback_t =
-        std::function<void(Window&, int, int, int, int)>;
 
     Window();
     ~Window();
@@ -66,17 +71,20 @@ struct Window final {
     Window& set_fullscreen(bool use_fullscreen);
 
     void set_resizecallback(on_resizecallback_t f) { on_resize_ = f; }
-    void set_keyboardcallback(on_keyboardcallback_t f) { on_keyboard_ = f; }
+
 
     bool visible() const;
     Window& set_visible(bool is_visible);
 
+    const KeyboardInputStack& keyboard_input() const;
+
   private:
     struct impl;
     std::unique_ptr<impl> impl_;
 
     on_resizecallback_t on_resize_;
-    on_keyboardcallback_t on_keyboard_;
+
+
 };
 
 } // namespace paradiso
diff --git a/src/lib/src/renderer.cpp b/src/lib/src/renderer.cpp
index 2898c0d..eccb289 100644
--- a/src/lib/src/renderer.cpp
+++ b/src/lib/src/renderer.cpp
@@ -38,14 +38,14 @@ namespace paradiso {
 struct Renderer::impl {
 
     uint64_t change_count{std::numeric_limits<uint64_t>::max()};
+    uint64_t change_count_texture{std::numeric_limits<uint64_t>::max()};
 
+    // below corresponds to GL state
     uint32_t vertex_array_obj{};
     uint32_t element_buffer_obj{};
     std::vector<uint32_t> vertex_buffer_ob{};
     uint32_t texture_id{};
 
-    impl() = default;
-
     ~impl() { release(); }
 
     bool ready() const {
@@ -153,7 +153,7 @@ struct Renderer::impl {
             glGenerateMipmap(GL_TEXTURE_2D);
             glGenerateTextureMipmap(texture_id);
 
-        } else {
+        } else if (image.change_count != change_count_texture) {
 
             glActiveTexture(GL_TEXTURE0);
             glBindTexture(GL_TEXTURE_2D, texture_id);
@@ -169,6 +169,8 @@ struct Renderer::impl {
                             GL_BGRA,            // format
                             GL_UNSIGNED_BYTE,   // type
                             image.data.data()); // pointer
+
+            change_count_texture = image.change_count;
         }
 
         glBindTexture(GL_TEXTURE_2D, 0);
diff --git a/src/lib/src/shader.cpp b/src/lib/src/shader.cpp
index 47d5070..7ed3fa5 100644
--- a/src/lib/src/shader.cpp
+++ b/src/lib/src/shader.cpp
@@ -22,6 +22,8 @@
  */
 #include "paradiso/shader.hpp"
 
+#include "shader_sprite.hpp"
+
 #include "glad/glad.h"
 
 #include <iostream>
@@ -199,6 +201,18 @@ Shader::~Shader() {}
 
 bool Shader::ready() const { return impl_->is_valid(); }
 
+bool Shader::load_preset(Preset preset) {
+    switch (preset) {
+    case Preset::Sprite:
+        this->set_source(paradiso::Shader::Type::Vertex, sprite_unlit_vertex);
+        this->set_source(paradiso::Shader::Type::Fragment,
+                         sprite_unlit_fragment);
+        break;
+    }
+
+    return build();
+}
+
 const Shader& Shader::set_uniform_at_location(int location, float v) const {
     impl_->bind(location, v);
     return *this;
diff --git a/src/lib/src/shader_sprite.hpp b/src/lib/src/shader_sprite.hpp
new file mode 100644
index 0000000..fc4c15d
--- /dev/null
+++ b/src/lib/src/shader_sprite.hpp
@@ -0,0 +1,83 @@
+/*
+ * Copyright 2023 Hartmut Seichter
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ *
+ */
+#ifndef PARADISO_SHADER_SPRITE_HPP
+#define PARADISO_SHADER_SPRITE_HPP
+
+namespace paradiso {
+
+static constexpr auto sprite_unlit_vertex = R"(
+#version 400 core
+
+layout (location = 0) in vec3 vertices;
+layout (location = 1) in vec3 normals;
+layout (location = 2) in vec2 texture_coords;
+
+// pivot der sprite
+uniform vec2 pivot = vec2( 0.0, 0.0 );
+// scale 
+uniform vec2 scale = vec2( 1.0, 1.0 );
+// rotation
+uniform float rotation = 0.0;
+
+// wir sind natuerlich in homogenenen 3D Koordinaten unterwegs
+mat4 mm = mat4(
+    vec4( scale.x, 0.0, 0.0, 0.0),
+    vec4( 0.0, scale.y, 0.0, 0.0),
+    vec4( 0.0, 0.0, 1.0, 0.0),
+    vec4( pivot, 0.0, 1.0)
+);
+
+float sir = sin(rotation);
+float cor = cos(rotation);
+
+mat4 mr = mat4(
+    vec4( cor, sir, 0.0, 0.0),
+    vec4(-sir, cor, 0.0, 0.0),
+    vec4( 0.0, 0.0, 1.0, 0.0),
+    vec4( 0.0, 0.0, 0.0, 1.0)
+    );
+
+out vec2 tex_c; // das hier reicht die texturkoordinaten durch
+
+void main() {
+    tex_c = texture_coords; // umstaendlich aber notwendig
+    gl_Position = mm * mr * vec4(vertices, 1.0); // unsere eigentliche shader transformation
+}
+)";
+
+
+static constexpr auto sprite_unlit_fragment = R"(
+#version 400 core
+
+uniform sampler2D tex_color; // hier ist unsere sprite textur (bitmap)
+
+in vec2 tex_c; // da sind die texturkoordinaten wieder
+
+out vec4 frag_color; // das hier wird der output (pixelwert/fragment)
+
+void main() {
+    frag_color = texture(tex_color,tex_c);
+})";
+} // namespace paradiso
+
+#endif
\ No newline at end of file
diff --git a/src/lib/src/window.cpp b/src/lib/src/window.cpp
index cf5e0ef..4962439 100644
--- a/src/lib/src/window.cpp
+++ b/src/lib/src/window.cpp
@@ -39,6 +39,8 @@ struct Window::impl {
 
     GLFWwindow* window_ = nullptr;
 
+    KeyboardInputStack keyboard_input_{};
+
     std::tuple<int, int> _old_size;
     std::tuple<int, int> _old_pos;
 
@@ -79,12 +81,9 @@ struct Window::impl {
                              int action, int mods) {
         Window::impl* impl =
             static_cast<Window::impl*>(glfwGetWindowUserPointer(window));
-        impl->parent_.get().on_keyboard_(impl->parent_, key, scancode, action,
-                                         mods);
-        //        input::get()._key_code = scancode;
-        //        input::get()._key_pressed = action;
-        // action 0,1,2
-        //        std::cout << __FUNCTION__ << action <<  std::endl;
+
+        impl->keyboard_input_.emplace(KeyboardInput{
+            .key = key, .scancode = scancode, .action = action, .mods = mods});
     }
 
     static void charmods_callback(GLFWwindow* window, unsigned int codepoint,
@@ -179,9 +178,10 @@ struct Window::impl {
 
     bool update(Window::on_updatecallback_t cb) {
         if (window_ && !glfwWindowShouldClose(window_)) {
-            // TODO lock and unlock the current input system to allow for late
-            // events coming in
-            //            input::get().reset();
+
+            // delete events
+            paradiso::Window::KeyboardInputStack{}.swap(keyboard_input_);
+
 
             // get new events
             glfwPollEvents();
@@ -263,10 +263,8 @@ struct Window::impl {
 //
 //
 Window::Window()
-    : impl_(std::make_unique<Window::impl>(*this)), on_resize_([](Window&) {}),
-      on_keyboard_([](Window&, int, int, int, int) {})
-
-{}
+    : impl_(std::make_unique<Window::impl>(*this)), on_resize_([](Window&) {}) {
+}
 
 Window::~Window() {}
 
@@ -308,4 +306,9 @@ Window& Window::set_title(std::string_view title) {
     impl_->set_title(title);
     return *this;
 }
+const Window::KeyboardInputStack& Window::keyboard_input() const {
+    return impl_->keyboard_input_;
+}
+
+
 } // namespace paradiso