diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..42afabf
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+/build
\ No newline at end of file
diff --git a/CMakeLists.txt b/CMakeLists.txt
new file mode 100644
index 0000000..20f3b1c
--- /dev/null
+++ b/CMakeLists.txt
@@ -0,0 +1,57 @@
+cmake_minimum_required(VERSION 3.16)
+project(VRModelViewer VERSION 0.1.0 LANGUAGES CXX)
+
+set(CMAKE_CXX_STANDARD 17)
+set(CMAKE_CXX_STANDARD_REQUIRED ON)
+set(CMAKE_EXPORT_COMPILE_COMMANDS ON)
+
+if(NOT CMAKE_BUILD_TYPE)
+  set(CMAKE_BUILD_TYPE Debug)
+endif()
+
+find_package(OpenSceneGraph REQUIRED COMPONENTS
+  osgDB osgGA osgUtil osgViewer osgText osgSim)
+find_package(assimp REQUIRED)
+find_package(OpenGL REQUIRED)
+find_package(PkgConfig REQUIRED)
+pkg_check_modules(IMGUI REQUIRED imgui)
+
+set(SOURCES
+  src/main.cpp
+  src/Application.cpp
+  src/ModelLoader.cpp
+  src/MorphManager.cpp
+  src/ImGuiLayer.cpp
+  src/SceneBuilder.cpp
+  src/OrbitManipulator.cpp
+  src/ShaderManager.cpp
+  src/AppConfig.cpp
+)
+
+add_executable(${PROJECT_NAME} ${SOURCES})
+
+target_include_directories(${PROJECT_NAME} PRIVATE
+  ${CMAKE_SOURCE_DIR}/include
+  ${OPENSCENEGRAPH_INCLUDE_DIRS}
+  ${ASSIMP_INCLUDE_DIRS}
+  ${IMGUI_INCLUDE_DIRS}
+)
+
+target_link_libraries(${PROJECT_NAME} PRIVATE
+  ${OPENSCENEGRAPH_LIBRARIES}
+  ${ASSIMP_LIBRARIES}
+  ${IMGUI_LIBRARIES}
+  OpenGL::GL
+)
+
+target_compile_options(${PROJECT_NAME} PRIVATE
+  $<$<CXX_COMPILER_ID:GNU,Clang>:-Wall -Wextra -Wpedantic>
+  ${IMGUI_CFLAGS_OTHER}
+)
+
+add_custom_target(copy_assets ALL
+  COMMAND ${CMAKE_COMMAND} -E copy_directory
+    ${CMAKE_SOURCE_DIR}/assets ${CMAKE_BINARY_DIR}/assets
+  COMMENT "Copying assets to build directory"
+)
+add_dependencies(${PROJECT_NAME} copy_assets)
diff --git a/README.md b/README.md
index e69de29..751ed23 100644
--- a/README.md
+++ b/README.md
@@ -0,0 +1,71 @@
+# VR Model Viewer
+
+Interactive 3-D model viewer built with **OpenSceneGraph** and **Assimp**.  
+Designed for inspecting PMX (MikuMikuDance), FBX, OBJ and other model formats.
+
+## Dependencies (already installed on Gentoo)
+
+| Library | Gentoo package |
+|---------|----------------|
+| OpenSceneGraph ≥ 3.6 | `dev-games/openscenegraph` |
+| Assimp ≥ 5.0 | `media-libs/assimp` |
+| CMake ≥ 3.16 | `dev-build/cmake` |
+| GCC / Clang (C++17) | `sys-devel/gcc` |
+
+## Build
+
+```bash
+# From the project root:
+cmake -S . -B build -DCMAKE_BUILD_TYPE=Debug
+cmake --build build --parallel $(nproc)
+```
+
+Or inside VSCodium press **Ctrl+Shift+B** → *Configure + Build*.
+
+## Run
+
+```bash
+./build/VRModelViewer path/to/model.pmx
+# or
+./build/VRModelViewer path/to/model.fbx
+```
+
+## Controls
+
+| Input | Action |
+|-------|--------|
+| **LMB drag** | Orbit camera |
+| **MMB drag** | Pan |
+| **Scroll** | Zoom (dolly) |
+| **R** | Reset camera to default humanoid view |
+| **F / Space** | Frame whole scene |
+| **S** | Toggle stats overlay (FPS, draw calls) |
+| **Esc** | Quit |
+
+## Project structure
+
+```
+vr_model_viewer/
+├── CMakeLists.txt
+├── include/
+│   ├── Application.h       # Top-level app / viewer owner
+│   ├── ModelLoader.h       # Assimp → OSG conversion
+│   ├── SceneBuilder.h      # Grid, axes, lights helpers
+│   └── OrbitManipulator.h  # Tweaked orbit camera
+├── src/
+│   ├── main.cpp
+│   ├── Application.cpp
+│   ├── ModelLoader.cpp
+│   ├── SceneBuilder.cpp
+│   └── OrbitManipulator.cpp
+└── assets/
+    └── models/             # drop your .pmx / .fbx files here
+```
+
+## Roadmap
+
+- [x] Phase 1 – Basic render pipeline + PMX/FBX loading
+- [ ] Phase 2 – Model placement & transform gizmos
+- [ ] Phase 3 – Bone / pose inspector
+- [ ] Phase 4 – ImGui UI panel
+- [ ] Phase 5 – VR headset integration (OpenXR)
diff --git a/assets/config.ini b/assets/config.ini
new file mode 100644
index 0000000..9e3f9e0
--- /dev/null
+++ b/assets/config.ini
@@ -0,0 +1,21 @@
+# VR Model Viewer configuration
+# Lines starting with # are comments.
+
+[ui]
+# Path to a TTF/OTF font file with CJK coverage.
+# Kochi Gothic is a good choice on Gentoo:
+#   /usr/share/fonts/kochi-substitute/kochi-gothic-subst.ttf
+# Leave blank to use ImGui's built-in ASCII-only font.
+font_path = /usr/share/fonts/kochi-substitute/kochi-gothic-subst.ttf
+
+# Font size in pixels
+font_size = 14
+
+# Starting width of the morph panel in pixels
+panel_width = 380
+
+[model]
+# Initial scale applied to the loaded model.
+# FBX exports from Blender are often 100x too large (cm vs m units).
+# Try 0.01 if your model appears huge, 1.0 if it looks correct.
+scale = 0.01
\ No newline at end of file
diff --git a/assets/shaders/cel.frag b/assets/shaders/cel.frag
new file mode 100644
index 0000000..d5ea56c
--- /dev/null
+++ b/assets/shaders/cel.frag
@@ -0,0 +1,37 @@
+#version 130
+
+varying vec3 v_normalVS;
+varying vec3 v_posVS;
+varying vec2 v_uv;
+varying vec4 v_color;
+
+uniform sampler2D osg_Sampler0;
+uniform bool      u_hasTexture;
+uniform vec3      u_lightDirVS;
+uniform vec3      u_lightColor;
+uniform vec3      u_ambientColor;
+uniform int       u_bands;
+uniform float     u_bandSharpness;
+
+float celQuantise(float value, int bands) {
+    float b = float(bands);
+    return floor(value * b + 0.5) / b;
+}
+
+void main() {
+    vec3 N = normalize(v_normalVS);
+    vec3 L = normalize(u_lightDirVS);
+
+    // Half-lambert so shadows aren't pitch black
+    float NdL    = dot(N, L) * 0.5 + 0.5;
+    float celVal = celQuantise(NdL, u_bands);
+
+    vec4 baseColor = u_hasTexture
+        ? texture2D(osg_Sampler0, v_uv)
+        : v_color;
+
+    vec3 diffuse = baseColor.rgb * u_lightColor  * celVal;
+    vec3 ambient = baseColor.rgb * u_ambientColor;
+
+    gl_FragColor = vec4(ambient + diffuse, baseColor.a);
+}
diff --git a/assets/shaders/cel.vert b/assets/shaders/cel.vert
new file mode 100644
index 0000000..207c8d7
--- /dev/null
+++ b/assets/shaders/cel.vert
@@ -0,0 +1,19 @@
+#version 130
+
+// OSG binds these automatically via Program::addBindAttribLocation
+// or via the fixed-function compatibility aliases in core profile.
+// Using built-in compatibility varyings is the safest approach with OSG 3.6.
+
+varying vec3 v_normalVS;
+varying vec3 v_posVS;
+varying vec2 v_uv;
+varying vec4 v_color;
+
+void main() {
+    vec4 posVS  = gl_ModelViewMatrix * gl_Vertex;
+    v_posVS     = posVS.xyz;
+    v_normalVS  = normalize(gl_NormalMatrix * gl_Normal);
+    v_uv        = gl_MultiTexCoord0.xy;
+    v_color     = gl_Color;
+    gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex;
+}
diff --git a/assets/shaders/toon.frag b/assets/shaders/toon.frag
new file mode 100644
index 0000000..278b8af
--- /dev/null
+++ b/assets/shaders/toon.frag
@@ -0,0 +1,56 @@
+#version 130
+
+varying vec3 v_normalVS;
+varying vec3 v_posVS;
+varying vec2 v_uv;
+varying vec4 v_color;
+
+uniform sampler2D osg_Sampler0;
+uniform bool      u_hasTexture;
+uniform vec3      u_lightDirVS;
+uniform vec3      u_lightColor;
+uniform vec3      u_ambientColor;
+uniform vec3      u_outlineColor;
+uniform bool      u_outlinePass;
+uniform int       u_bands;
+uniform float     u_specularThreshold;
+uniform float     u_specularIntensity;
+uniform float     u_rimThreshold;
+uniform float     u_rimIntensity;
+uniform vec3      u_rimColor;
+
+float celStep(float value, int bands) {
+    return floor(value * float(bands) + 0.5) / float(bands);
+}
+
+void main() {
+    if (u_outlinePass) {
+        gl_FragColor = vec4(u_outlineColor, 1.0);
+        return;
+    }
+
+    vec3 N = normalize(v_normalVS);
+    vec3 L = normalize(u_lightDirVS);
+    vec3 V = normalize(-v_posVS);
+
+    // Cel diffuse
+    float NdL    = dot(N, L) * 0.5 + 0.5;
+    float celDif = celStep(NdL, u_bands);
+
+    // Snap specular
+    vec3  H    = normalize(L + V);
+    float NdH  = max(dot(N, H), 0.0);
+    float spec = step(u_specularThreshold, NdH) * u_specularIntensity;
+
+    // Rim light
+    float rim  = 1.0 - max(dot(N, V), 0.0);
+    rim        = step(u_rimThreshold, rim) * u_rimIntensity;
+
+    vec4 base    = u_hasTexture ? texture2D(osg_Sampler0, v_uv) : v_color;
+    vec3 ambient = base.rgb * u_ambientColor;
+    vec3 diffuse = base.rgb * u_lightColor * celDif;
+    vec3 specCol = u_lightColor * spec;
+    vec3 rimCol  = u_rimColor   * rim;
+
+    gl_FragColor = vec4(ambient + diffuse + specCol + rimCol, base.a);
+}
diff --git a/assets/shaders/toon.vert b/assets/shaders/toon.vert
new file mode 100644
index 0000000..795eddb
--- /dev/null
+++ b/assets/shaders/toon.vert
@@ -0,0 +1,25 @@
+#version 130
+
+uniform bool  u_outlinePass;
+uniform float u_outlineWidth;
+
+varying vec3 v_normalVS;
+varying vec3 v_posVS;
+varying vec2 v_uv;
+varying vec4 v_color;
+
+void main() {
+    vec3 pos = gl_Vertex.xyz;
+
+    if (u_outlinePass) {
+        pos += gl_Normal * u_outlineWidth;
+    }
+
+    vec4 posVS = gl_ModelViewMatrix * vec4(pos, 1.0);
+    v_posVS    = posVS.xyz;
+    v_normalVS = normalize(gl_NormalMatrix * gl_Normal);
+    v_uv       = gl_MultiTexCoord0.xy;
+    v_color    = gl_Color;
+
+    gl_Position = gl_ModelViewProjectionMatrix * vec4(pos, 1.0);
+}
diff --git a/include/AppConfig.h b/include/AppConfig.h
new file mode 100644
index 0000000..9c1c1bd
--- /dev/null
+++ b/include/AppConfig.h
@@ -0,0 +1,35 @@
+#pragma once
+
+#include <string>
+#include <unordered_map>
+
+/**
+ * AppConfig
+ * ---------
+ * Minimal INI-style config file reader.
+ * Supports [sections], key = value pairs, and # comments.
+ *
+ * Keys are accessed as "section.key", e.g. "ui.font_path".
+ * Missing keys return a provided default value.
+ *
+ * The config file is searched in this order:
+ *   1. Next to the executable:  <exeDir>/assets/config.ini
+ *   2. Current working dir:     assets/config.ini
+ */
+class AppConfig {
+public:
+    /// Load config. Returns true if a file was found and parsed.
+    bool load();
+
+    std::string getString(const std::string& key,
+                          const std::string& defaultVal = "") const;
+
+    float       getFloat(const std::string& key,
+                         float              defaultVal = 0.f) const;
+
+    int         getInt(const std::string& key,
+                       int                defaultVal = 0) const;
+
+private:
+    std::unordered_map<std::string, std::string> m_values;
+};
diff --git a/include/Application.h b/include/Application.h
new file mode 100644
index 0000000..a2c3542
--- /dev/null
+++ b/include/Application.h
@@ -0,0 +1,59 @@
+#pragma once
+
+#include <string>
+#include <memory>
+#include <mutex>
+
+#include <osgViewer/Viewer>
+#include <osg/ref_ptr>
+#include <osg/Group>
+#include <osg/Node>
+#include <osg/NodeCallback>
+#include <osg/MatrixTransform>
+#include <osgGA/GUIEventHandler>
+
+#include "ShaderManager.h"
+#include "AppConfig.h"
+
+class MorphManager;
+class ImGuiLayer;
+
+class Application : public osgGA::GUIEventHandler {
+public:
+    Application();
+    ~Application();
+
+    bool init(int width = 1280, int height = 720,
+              const std::string& title = "VR Model Viewer");
+    bool loadModel(const std::string& filepath);
+    int  run();
+
+    bool handle(const osgGA::GUIEventAdapter& ea,
+                osgGA::GUIActionAdapter&      aa) override;
+
+    void applyPendingShader();   // called by update callback
+    void applyMorphWeights();    // called by update callback
+
+private:
+    void setupLighting();
+    void setupGrid();
+    void requestShader(const std::string& mode);
+    void setModelScale(float scale);
+
+    osg::ref_ptr<osgViewer::Viewer> m_viewer;
+    osg::ref_ptr<osg::Group>        m_sceneRoot;
+    osg::ref_ptr<osg::Group>        m_shaderGroup;
+    osg::ref_ptr<osg::Node>            m_modelNode;
+    osg::ref_ptr<osg::MatrixTransform> m_modelXform;  // scale/transform wrapper
+
+    AppConfig                       m_config;
+    std::unique_ptr<ShaderManager>  m_shaderMgr;
+    std::unique_ptr<MorphManager>   m_morphMgr;
+    std::unique_ptr<ImGuiLayer>     m_imguiLayer;
+
+    std::mutex   m_shaderMutex;
+    std::string  m_pendingShader;
+    std::string  m_currentShader = "toon";
+    bool         m_shaderDirty   = false;
+    bool         m_reloadShaders = false;
+};
\ No newline at end of file
diff --git a/include/ImGuiLayer.h b/include/ImGuiLayer.h
new file mode 100644
index 0000000..6fce448
--- /dev/null
+++ b/include/ImGuiLayer.h
@@ -0,0 +1,51 @@
+#pragma once
+
+#include <string>
+#include <functional>
+#include <osg/Camera>
+#include <osgViewer/Viewer>
+#include <osgGA/GUIEventAdapter>
+
+class MorphManager;
+class AppConfig;
+
+class ImGuiLayer {
+public:
+    explicit ImGuiLayer(MorphManager* morphMgr, const AppConfig* cfg);
+    ~ImGuiLayer();
+
+    void init(osgViewer::Viewer* viewer);
+    bool handleEvent(const osgGA::GUIEventAdapter& ea);
+
+    void renderPanel();         // called by ImGuiDrawCallback each frame
+    void markGLInitialized();
+
+    // Callbacks set by Application so ImGui can drive app state
+    std::function<void(const std::string&)> onShaderChange;
+    std::function<void()>                   onShaderReload;
+    std::function<void(float)>              onScaleChange;
+
+    // Called by Application each frame so the shader tab shows current state
+    void setCurrentShader(const std::string& s) { m_currentShader = s; }
+    void setInitialScale(float s) { m_scale = s; m_scaleBuf[0] = 0; }
+
+private:
+    void renderMorphTab();
+    void renderShaderTab();
+    void renderTransformTab();
+
+    MorphManager*             m_morphMgr       = nullptr;
+    const AppConfig*          m_cfg            = nullptr;
+    osgViewer::Viewer*        m_viewer         = nullptr;
+    osg::ref_ptr<osg::Camera> m_camera;
+
+    bool  m_contextCreated = false;
+    bool  m_glInitialized  = false;
+    float m_panelWidth     = 380.f;  // wider default so names are visible
+
+    char  m_searchBuf[256] = {};
+    bool  m_showOnlyActive = false;
+    std::string m_currentShader = "toon";
+    float       m_scale         = 1.0f;
+    char        m_scaleBuf[32]  = {};
+};
\ No newline at end of file
diff --git a/include/ModelLoader.h b/include/ModelLoader.h
new file mode 100644
index 0000000..82db0a1
--- /dev/null
+++ b/include/ModelLoader.h
@@ -0,0 +1,20 @@
+#pragma once
+
+#include <string>
+#include <osg/ref_ptr>
+#include <osg/Node>
+
+class MorphManager;
+
+class ModelLoader {
+public:
+    ModelLoader() = default;
+
+    osg::ref_ptr<osg::Node> load(const std::string& filepath,
+                                 MorphManager*       morphMgr = nullptr);
+
+private:
+    osg::ref_ptr<osg::Node> buildOsgScene(const struct aiScene* scene,
+                                          const std::string&    baseDir,
+                                          MorphManager*         morphMgr);
+};
\ No newline at end of file
diff --git a/include/MorphManager.h b/include/MorphManager.h
new file mode 100644
index 0000000..ffb8ce6
--- /dev/null
+++ b/include/MorphManager.h
@@ -0,0 +1,83 @@
+#pragma once
+
+#include <string>
+#include <vector>
+#include <unordered_map>
+
+#include <osg/ref_ptr>
+#include <osg/Geometry>
+#include <osg/Array>
+
+/**
+ * MorphManager
+ * ------------
+ * Stores morph target data for all meshes in a loaded model and applies
+ * weighted blends every frame on the CPU.
+ *
+ * Usage:
+ *   // At load time (ModelLoader calls these):
+ *   mgr.registerMesh(geom, baseVerts, baseNormals);
+ *   mgr.addTarget(geom, "blink", deltaVerts, deltaNormals);
+ *
+ *   // Every frame (update callback calls this):
+ *   mgr.applyWeights();
+ *
+ *   // From ImGui (slider changed):
+ *   mgr.setWeight("blink", 0.75f);
+ */
+class MorphManager {
+public:
+    MorphManager() = default;
+
+    // ── Registration (called at load time) ───────────────────────────────────
+
+    /// Register a geometry's base vertex/normal arrays.
+    /// Must be called before addTarget() for this geometry.
+    void registerMesh(osg::Geometry*              geom,
+                      osg::ref_ptr<osg::Vec3Array> baseVerts,
+                      osg::ref_ptr<osg::Vec3Array> baseNormals);
+
+    /// Add one morph target for a geometry.
+    /// deltaVerts/deltaNormals are OFFSETS from the base (not absolute positions).
+    void addTarget(osg::Geometry*              geom,
+                   const std::string&           name,
+                   osg::ref_ptr<osg::Vec3Array> deltaVerts,
+                   osg::ref_ptr<osg::Vec3Array> deltaNormals);
+
+    // ── Weight control ───────────────────────────────────────────────────────
+
+    void  setWeight(const std::string& name, float weight);
+    float getWeight(const std::string& name) const;
+    void  resetAll();
+
+    /// Returns all unique morph names across all meshes, sorted.
+    const std::vector<std::string>& morphNames() const { return m_morphNames; }
+
+    // ── Per-frame update ─────────────────────────────────────────────────────
+
+    /// Blend all active morphs into each geometry's live vertex/normal arrays
+    /// and dirty them so OSG re-uploads to the GPU.
+    void applyWeights();
+
+private:
+    // One morph target contribution for a single geometry
+    struct Target {
+        std::string                  name;
+        osg::ref_ptr<osg::Vec3Array> deltaVerts;
+        osg::ref_ptr<osg::Vec3Array> deltaNormals;
+    };
+
+    // Per-geometry morph data
+    struct MeshEntry {
+        osg::Geometry*               geom        = nullptr;
+        osg::ref_ptr<osg::Vec3Array> baseVerts;
+        osg::ref_ptr<osg::Vec3Array> baseNormals;
+        std::vector<Target>          targets;
+    };
+
+    std::vector<MeshEntry>                     m_meshes;
+    std::unordered_map<std::string, float>     m_weights;   // name → 0..1
+    std::vector<std::string>                   m_morphNames; // sorted unique list
+
+    void rebuildNameList();
+};
diff --git a/include/OrbitManipulator.h b/include/OrbitManipulator.h
new file mode 100644
index 0000000..91a633f
--- /dev/null
+++ b/include/OrbitManipulator.h
@@ -0,0 +1,29 @@
+#pragma once
+
+#include <osgGA/OrbitManipulator>
+
+/**
+ * OrbitManipulator
+ * ----------------
+ * Thin subclass of osgGA::OrbitManipulator that tweaks defaults for
+ * inspecting character models:
+ *   - LMB drag  → orbit
+ *   - MMB drag  → pan
+ *   - Scroll    → dolly
+ *   - F key     → frame the whole scene
+ *   - R key     → reset to default view
+ *
+ * The manipulator targets the scene centre, with a configurable
+ * initial eye offset.
+ */
+class OrbitManipulator : public osgGA::OrbitManipulator {
+public:
+    OrbitManipulator();
+
+    /// Set a comfortable starting position for viewing a humanoid model.
+    void setDefaultHumanoidView();
+
+protected:
+    bool handleKeyDown(const osgGA::GUIEventAdapter& ea,
+                       osgGA::GUIActionAdapter&      aa) override;
+};
diff --git a/include/SceneBuilder.h b/include/SceneBuilder.h
new file mode 100644
index 0000000..1df5f09
--- /dev/null
+++ b/include/SceneBuilder.h
@@ -0,0 +1,34 @@
+#pragma once
+
+#include <osg/ref_ptr>
+#include <osg/Group>
+#include <osg/Geode>
+#include <osg/Geometry>
+#include <osg/Light>
+#include <osg/LightSource>
+
+/**
+ * SceneBuilder
+ * ------------
+ * Factory helpers for common scene-graph elements:
+ *   - reference floor grid
+ *   - ambient + directional lights
+ *   - axes gizmo (X/Y/Z)
+ */
+class SceneBuilder {
+public:
+    /// Create a flat grid centred at the origin.
+    /// @param halfSize  half-extent of the grid in world units
+    /// @param divisions number of cells per side
+    static osg::ref_ptr<osg::Geode> createGrid(float halfSize = 10.f,
+                                                int   divisions = 20);
+
+    /// Create a simple 3-axis gizmo (red=X, green=Y, blue=Z).
+    static osg::ref_ptr<osg::Geode> createAxes(float length = 1.f);
+
+    /// Build a LightSource node suitable for a warm key light.
+    static osg::ref_ptr<osg::LightSource> createSunLight(int lightNum = 0);
+
+    /// Build an ambient fill light.
+    static osg::ref_ptr<osg::LightSource> createAmbientLight(int lightNum = 1);
+};
diff --git a/include/ShaderManager.h b/include/ShaderManager.h
new file mode 100644
index 0000000..88ca170
--- /dev/null
+++ b/include/ShaderManager.h
@@ -0,0 +1,51 @@
+#pragma once
+
+#include <string>
+#include <unordered_map>
+
+#include <osg/ref_ptr>
+#include <osg/Program>
+#include <osg/Node>
+#include <osg/StateSet>
+
+/**
+ * ShaderManager
+ * -------------
+ * Loads, caches, and applies GLSL shader programs to OSG nodes.
+ *
+ * Supported modes (toggled at runtime via applyTo):
+ *   "flat"  – unlit, texture/vertex colour only
+ *   "cel"   – quantised diffuse bands
+ *   "toon"  – cel + hard specular + rim light + outline shell
+ *
+ * Shaders are loaded from `shaderDir` (default: assets/shaders/).
+ * Editing the .glsl files and calling reload() hot-reloads them.
+ */
+class ShaderManager {
+public:
+    explicit ShaderManager(const std::string& shaderDir = "assets/shaders");
+
+    /// Apply a named shader mode to `node`'s StateSet.
+    /// Also sets sensible default uniforms.
+    void applyTo(osg::Node* node, const std::string& mode);
+
+    /// Re-read all .glsl files from disk (call after editing shaders).
+    void reload();
+
+    /// Update the light direction uniform on an already-shaded node
+    /// (call when the light moves). `dirVS` should be in view space.
+    static void setLightDir(osg::StateSet* ss, const osg::Vec3f& dirVS);
+
+private:
+    osg::ref_ptr<osg::Program> buildProgram(const std::string& vertFile,
+                                             const std::string& fragFile);
+
+    void setCommonUniforms(osg::StateSet* ss);
+    void setCelUniforms   (osg::StateSet* ss);
+    void setToonUniforms  (osg::StateSet* ss);
+
+    std::string m_shaderDir;
+
+    // Cache: mode name → compiled program
+    std::unordered_map<std::string, osg::ref_ptr<osg::Program>> m_programs;
+};