diff --git a/src/services/interfaces/i_audio_service.hpp b/src/services/interfaces/i_audio_service.hpp
new file mode 100644
index 0000000..9dc7aff
--- /dev/null
+++ b/src/services/interfaces/i_audio_service.hpp
@@ -0,0 +1,84 @@
+#pragma once
+
+#include <filesystem>
+
+namespace sdl3cpp::services {
+
+/**
+ * @brief Audio playback service interface.
+ *
+ * Handles background music and sound effect playback using SDL audio.
+ * Wraps the AudioPlayer class with a clean service interface.
+ */
+class IAudioService {
+public:
+    virtual ~IAudioService() = default;
+
+    /**
+     * @brief Initialize the audio subsystem.
+     *
+     * @throws std::runtime_error if audio initialization fails
+     */
+    virtual void Initialize() = 0;
+
+    /**
+     * @brief Shutdown the audio subsystem and stop all playback.
+     */
+    virtual void Shutdown() = 0;
+
+    /**
+     * @brief Play a background music track.
+     *
+     * Only one background track can play at a time. Calling this
+     * method will stop any currently playing background music.
+     *
+     * @param path Path to the audio file (OGG, WAV, etc.)
+     * @param loop Whether to loop the track
+     * @throws std::runtime_error if file cannot be loaded
+     */
+    virtual void PlayBackground(const std::filesystem::path& path, bool loop = true) = 0;
+
+    /**
+     * @brief Play a sound effect.
+     *
+     * Multiple sound effects can play simultaneously.
+     *
+     * @param path Path to the audio file
+     * @param loop Whether to loop the effect (usually false)
+     * @throws std::runtime_error if file cannot be loaded
+     */
+    virtual void PlayEffect(const std::filesystem::path& path, bool loop = false) = 0;
+
+    /**
+     * @brief Stop background music playback.
+     */
+    virtual void StopBackground() = 0;
+
+    /**
+     * @brief Stop all audio playback (background and effects).
+     */
+    virtual void StopAll() = 0;
+
+    /**
+     * @brief Set master volume.
+     *
+     * @param volume Volume level from 0.0 (silent) to 1.0 (full)
+     */
+    virtual void SetVolume(float volume) = 0;
+
+    /**
+     * @brief Get the current master volume.
+     *
+     * @return Volume level from 0.0 to 1.0
+     */
+    virtual float GetVolume() const = 0;
+
+    /**
+     * @brief Check if background music is currently playing.
+     *
+     * @return true if playing, false otherwise
+     */
+    virtual bool IsBackgroundPlaying() const = 0;
+};
+
+}  // namespace sdl3cpp::services
diff --git a/src/services/interfaces/i_config_service.hpp b/src/services/interfaces/i_config_service.hpp
new file mode 100644
index 0000000..2ab2608
--- /dev/null
+++ b/src/services/interfaces/i_config_service.hpp
@@ -0,0 +1,56 @@
+#pragma once
+
+#include <cstdint>
+#include <filesystem>
+#include <string>
+
+namespace sdl3cpp::services {
+
+/**
+ * @brief Configuration service interface.
+ *
+ * Provides access to application configuration loaded from JSON or defaults.
+ * Similar to Spring's @ConfigurationProperties.
+ */
+class IConfigService {
+public:
+    virtual ~IConfigService() = default;
+
+    /**
+     * @brief Get the configured window width.
+     * @return Window width in pixels
+     */
+    virtual uint32_t GetWindowWidth() const = 0;
+
+    /**
+     * @brief Get the configured window height.
+     * @return Window height in pixels
+     */
+    virtual uint32_t GetWindowHeight() const = 0;
+
+    /**
+     * @brief Get the path to the Lua script to execute.
+     * @return Path to the script file
+     */
+    virtual std::filesystem::path GetScriptPath() const = 0;
+
+    /**
+     * @brief Check if Lua debug mode is enabled.
+     * @return true if debug mode is enabled, false otherwise
+     */
+    virtual bool IsLuaDebugEnabled() const = 0;
+
+    /**
+     * @brief Get the window title.
+     * @return Window title string
+     */
+    virtual std::string GetWindowTitle() const = 0;
+
+    /**
+     * @brief Get required Vulkan device extensions.
+     * @return List of extension names
+     */
+    virtual std::vector<const char*> GetDeviceExtensions() const = 0;
+};
+
+}  // namespace sdl3cpp::services
diff --git a/src/services/interfaces/i_graphics_service.hpp b/src/services/interfaces/i_graphics_service.hpp
new file mode 100644
index 0000000..ef79022
--- /dev/null
+++ b/src/services/interfaces/i_graphics_service.hpp
@@ -0,0 +1,184 @@
+#pragma once
+
+#include "../../core/vertex.hpp"
+#include <array>
+#include <cstdint>
+#include <string>
+#include <unordered_map>
+#include <vector>
+#include <vulkan/vulkan.h>
+
+// Forward declare SDL type
+struct SDL_Window;
+
+namespace sdl3cpp::services {
+
+/**
+ * @brief Graphics service configuration.
+ */
+struct GraphicsConfig {
+    std::vector<const char*> deviceExtensions;
+    VkFormat preferredFormat = VK_FORMAT_B8G8R8A8_SRGB;
+    bool enableValidationLayers = false;
+};
+
+/**
+ * @brief Shader file paths for a shader program.
+ */
+struct ShaderPaths {
+    std::string vertex;
+    std::string fragment;
+};
+
+/**
+ * @brief Render command for a single draw call.
+ */
+struct RenderCommand {
+    uint32_t indexOffset;
+    uint32_t indexCount;
+    int32_t vertexOffset;
+    std::string shaderKey;
+    std::array<float, 16> modelMatrix;
+};
+
+/**
+ * @brief Graphics service interface (Vulkan rendering).
+ *
+ * Abstracts all Vulkan rendering operations including device management,
+ * swapchain, pipelines, buffers, and rendering.
+ *
+ * This is the largest service, consolidating ~1,500 lines of Vulkan code
+ * from the original Sdl3App class.
+ */
+class IGraphicsService {
+public:
+    virtual ~IGraphicsService() = default;
+
+    /**
+     * @brief Initialize the Vulkan instance, device, and queues.
+     *
+     * @param window The SDL window to create a surface for
+     * @param config Graphics configuration
+     * @throws std::runtime_error if device initialization fails
+     */
+    virtual void InitializeDevice(SDL_Window* window, const GraphicsConfig& config) = 0;
+
+    /**
+     * @brief Initialize the swapchain for presenting rendered images.
+     *
+     * Must be called after InitializeDevice().
+     *
+     * @throws std::runtime_error if swapchain creation fails
+     */
+    virtual void InitializeSwapchain() = 0;
+
+    /**
+     * @brief Recreate the swapchain (e.g., after window resize).
+     *
+     * @throws std::runtime_error if swapchain recreation fails
+     */
+    virtual void RecreateSwapchain() = 0;
+
+    /**
+     * @brief Shutdown and release all Vulkan resources.
+     */
+    virtual void Shutdown() = 0;
+
+    /**
+     * @brief Load and compile shader programs.
+     *
+     * @param shaders Map of shader key to shader file paths
+     * @throws std::runtime_error if shader compilation fails
+     */
+    virtual void LoadShaders(const std::unordered_map<std::string, ShaderPaths>& shaders) = 0;
+
+    /**
+     * @brief Upload vertex data to GPU buffer.
+     *
+     * @param vertices Vector of vertex data
+     * @throws std::runtime_error if buffer creation fails
+     */
+    virtual void UploadVertexData(const std::vector<core::Vertex>& vertices) = 0;
+
+    /**
+     * @brief Upload index data to GPU buffer.
+     *
+     * @param indices Vector of index data
+     * @throws std::runtime_error if buffer creation fails
+     */
+    virtual void UploadIndexData(const std::vector<uint16_t>& indices) = 0;
+
+    /**
+     * @brief Begin a new frame and acquire the next swapchain image.
+     *
+     * @return true if successful, false if swapchain needs recreation
+     */
+    virtual bool BeginFrame() = 0;
+
+    /**
+     * @brief Render the scene with the given render commands.
+     *
+     * @param commands List of render commands to execute
+     * @param viewProj View-projection matrix
+     */
+    virtual void RenderScene(const std::vector<RenderCommand>& commands,
+                            const std::array<float, 16>& viewProj) = 0;
+
+    /**
+     * @brief End the frame and present the rendered image.
+     *
+     * @return true if successful, false if swapchain needs recreation
+     */
+    virtual bool EndFrame() = 0;
+
+    /**
+     * @brief Wait for all GPU operations to complete.
+     *
+     * Called before cleanup or when synchronization is needed.
+     */
+    virtual void WaitIdle() = 0;
+
+    /**
+     * @brief Get the Vulkan logical device.
+     *
+     * @return VkDevice handle (needed for GUI renderer, etc.)
+     */
+    virtual VkDevice GetDevice() const = 0;
+
+    /**
+     * @brief Get the Vulkan physical device.
+     *
+     * @return VkPhysicalDevice handle
+     */
+    virtual VkPhysicalDevice GetPhysicalDevice() const = 0;
+
+    /**
+     * @brief Get the current swapchain extent (framebuffer size).
+     *
+     * @return VkExtent2D with width and height
+     */
+    virtual VkExtent2D GetSwapchainExtent() const = 0;
+
+    /**
+     * @brief Get the swapchain image format.
+     *
+     * @return VkFormat of swapchain images
+     */
+    virtual VkFormat GetSwapchainFormat() const = 0;
+
+    /**
+     * @brief Get the current command buffer being recorded.
+     *
+     * @return VkCommandBuffer (needed for GUI rendering)
+     */
+    virtual VkCommandBuffer GetCurrentCommandBuffer() const = 0;
+
+    /**
+     * @brief Get the graphics queue.
+     *
+     * @return VkQueue handle
+     */
+    virtual VkQueue GetGraphicsQueue() const = 0;
+};
+
+}  // namespace sdl3cpp::services
diff --git a/src/services/interfaces/i_gui_service.hpp b/src/services/interfaces/i_gui_service.hpp
new file mode 100644
index 0000000..ba5b111
--- /dev/null
+++ b/src/services/interfaces/i_gui_service.hpp
@@ -0,0 +1,77 @@
+#pragma once
+
+#include <cstdint>
+#include <filesystem>
+#include <vector>
+#include <vulkan/vulkan.h>
+
+namespace sdl3cpp::services {
+
+// Forward declare GUI types
+struct GuiCommand;
+
+/**
+ * @brief GUI rendering service interface.
+ *
+ * Handles 2D GUI overlay rendering using Vulkan.
+ * Wraps the GuiRenderer class with support for SVG, text, and shapes.
+ */
+class IGuiService {
+public:
+    virtual ~IGuiService() = default;
+
+    /**
+     * @brief Initialize the GUI renderer.
+     *
+     * @param device Vulkan logical device
+     * @param physicalDevice Vulkan physical device
+     * @param format Swapchain image format
+     * @param resourcePath Path to GUI resources (fonts, SVG files, etc.)
+     * @throws std::runtime_error if initialization fails
+     */
+    virtual void Initialize(VkDevice device,
+                           VkPhysicalDevice physicalDevice,
+                           VkFormat format,
+                           const std::filesystem::path& resourcePath) = 0;
+
+    /**
+     * @brief Prepare GUI commands for rendering.
+     *
+     * Processes GUI commands from Lua and prepares rendering data.
+     *
+     * @param commands Vector of GUI commands to render
+     * @param width Viewport width in pixels
+     * @param height Viewport height in pixels
+     */
+    virtual void PrepareFrame(const std::vector<GuiCommand>& commands,
+                             uint32_t width,
+                             uint32_t height) = 0;
+
+    /**
+     * @brief Render GUI overlay to swapchain image.
+     *
+     * Records rendering commands into the provided command buffer.
+     *
+     * @param commandBuffer Vulkan command buffer to record into
+     * @param image Target swapchain image
+     */
+    virtual void RenderToSwapchain(VkCommandBuffer commandBuffer, VkImage image) = 0;
+
+    /**
+     * @brief Handle window resize.
+     *
+     * Recreates internal resources for the new window size.
+     *
+     * @param width New width in pixels
+     * @param height New height in pixels
+     * @param format Swapchain image format
+     */
+    virtual void Resize(uint32_t width, uint32_t height, VkFormat format) = 0;
+
+    /**
+     * @brief Shutdown and release GPU resources.
+     */
+    virtual void Shutdown() = 0;
+};
+
+}  // namespace sdl3cpp::services
diff --git a/src/services/interfaces/i_input_service.hpp b/src/services/interfaces/i_input_service.hpp
new file mode 100644
index 0000000..5d93e7d
--- /dev/null
+++ b/src/services/interfaces/i_input_service.hpp
@@ -0,0 +1,81 @@
+#pragma once
+
+#include <string>
+#include <unordered_set>
+#include <SDL3/SDL.h>
+
+namespace sdl3cpp::services {
+
+/**
+ * @brief Input state snapshot for a single frame.
+ */
+struct InputState {
+    float mouseX = 0.0f;
+    float mouseY = 0.0f;
+    float mouseWheelDeltaX = 0.0f;
+    float mouseWheelDeltaY = 0.0f;
+    std::unordered_set<SDL_Keycode> keysPressed;
+    std::unordered_set<uint8_t> mouseButtonsPressed;
+    std::string textInput;
+};
+
+/**
+ * @brief Input handling service interface.
+ *
+ * Subscribes to input events from the event bus and maintains
+ * the current input state for queries by other services.
+ */
+class IInputService {
+public:
+    virtual ~IInputService() = default;
+
+    /**
+     * @brief Process an SDL event and update input state.
+     *
+     * Called by the window service when events are polled.
+     * Updates internal state and publishes events to the event bus.
+     *
+     * @param event The SDL event to process
+     */
+    virtual void ProcessEvent(const SDL_Event& event) = 0;
+
+    /**
+     * @brief Reset per-frame input state.
+     *
+     * Called at the beginning of each frame to clear transient state
+     * like mouse wheel delta and text input.
+     */
+    virtual void ResetFrameState() = 0;
+
+    /**
+     * @brief Get the current input state.
+     *
+     * @return Reference to the current input state
+     */
+    virtual const InputState& GetState() const = 0;
+
+    /**
+     * @brief Check if a key is currently pressed.
+     *
+     * @param key The SDL keycode to check
+     * @return true if the key is pressed, false otherwise
+     */
+    virtual bool IsKeyPressed(SDL_Keycode key) const = 0;
+
+    /**
+     * @brief Check if a mouse button is currently pressed.
+     *
+     * @param button The mouse button (SDL_BUTTON_LEFT, SDL_BUTTON_RIGHT, etc.)
+     * @return true if the button is pressed, false otherwise
+     */
+    virtual bool IsMouseButtonPressed(uint8_t button) const = 0;
+
+    /**
+     * @brief Get the current mouse position.
+     *
+     * @return Pair of (x, y) coordinates in pixels
+     */
+    virtual std::pair<float, float> GetMousePosition() const = 0;
+};
+
+}  // namespace sdl3cpp::services
diff --git a/src/services/interfaces/i_physics_service.hpp b/src/services/interfaces/i_physics_service.hpp
new file mode 100644
index 0000000..7aeb793
--- /dev/null
+++ b/src/services/interfaces/i_physics_service.hpp
@@ -0,0 +1,133 @@
+#pragma once
+
+#include <string>
+#include <LinearMath/btVector3.h>
+#include <LinearMath/btTransform.h>
+
+namespace sdl3cpp::services {
+
+/**
+ * @brief Physics simulation service interface.
+ *
+ * Provides rigid body physics simulation using Bullet Physics.
+ * Wraps the PhysicsBridge class with a clean service interface.
+ */
+class IPhysicsService {
+public:
+    virtual ~IPhysicsService() = default;
+
+    /**
+     * @brief Initialize the physics world.
+     *
+     * @param gravity Gravity vector (default: {0, -9.8, 0})
+     */
+    virtual void Initialize(const btVector3& gravity = btVector3(0, -9.8f, 0)) = 0;
+
+    /**
+     * @brief Shutdown and release physics resources.
+     */
+    virtual void Shutdown() = 0;
+
+    /**
+     * @brief Add a box-shaped rigid body to the simulation.
+     *
+     * @param name Unique identifier for this body
+     * @param halfExtents Half-extents of the box (half width/height/depth)
+     * @param mass Mass in kg (0 for static objects)
+     * @param transform Initial position and rotation
+     * @return true if added successfully, false if name already exists
+     */
+    virtual bool AddBoxRigidBody(const std::string& name,
+                                 const btVector3& halfExtents,
+                                 float mass,
+                                 const btTransform& transform) = 0;
+
+    /**
+     * @brief Add a sphere-shaped rigid body to the simulation.
+     *
+     * @param name Unique identifier for this body
+     * @param radius Sphere radius
+     * @param mass Mass in kg (0 for static objects)
+     * @param transform Initial position and rotation
+     * @return true if added successfully, false if name already exists
+     */
+    virtual bool AddSphereRigidBody(const std::string& name,
+                                    float radius,
+                                    float mass,
+                                    const btTransform& transform) = 0;
+
+    /**
+     * @brief Remove a rigid body from the simulation.
+     *
+     * @param name Identifier of the body to remove
+     * @return true if removed, false if not found
+     */
+    virtual bool RemoveRigidBody(const std::string& name) = 0;
+
+    /**
+     * @brief Step the physics simulation forward in time.
+     *
+     * @param deltaTime Time step in seconds (typically 1/60)
+     * @param maxSubSteps Maximum number of sub-steps for stability
+     */
+    virtual void StepSimulation(float deltaTime, int maxSubSteps = 10) = 0;
+
+    /**
+     * @brief Get the current transform of a rigid body.
+     *
+     * @param name Identifier of the body
+     * @param outTransform Output parameter for the transform
+     * @return true if body exists, false otherwise
+     */
+    virtual bool GetTransform(const std::string& name, btTransform& outTransform) const = 0;
+
+    /**
+     * @brief Set the transform of a rigid body.
+     *
+     * @param name Identifier of the body
+     * @param transform New position and rotation
+     * @return true if body exists, false otherwise
+     */
+    virtual bool SetTransform(const std::string& name, const btTransform& transform) = 0;
+
+    /**
+     * @brief Apply a force to a rigid body.
+     *
+     * @param name Identifier of the body
+     * @param force Force vector in Newtons
+     * @return true if body exists, false otherwise
+     */
+    virtual bool ApplyForce(const std::string& name, const btVector3& force) = 0;
+
+    /**
+     * @brief Apply an impulse to a rigid body.
+     *
+     * @param name Identifier of the body
+     * @param impulse Impulse vector
+     * @return true if body exists, false otherwise
+     */
+    virtual bool ApplyImpulse(const std::string& name, const btVector3& impulse) = 0;
+
+    /**
+     * @brief Set the linear velocity of a rigid body.
+     *
+     * @param name Identifier of the body
+     * @param velocity Velocity vector in m/s
+     * @return true if body exists, false otherwise
+     */
+    virtual bool SetLinearVelocity(const std::string& name, const btVector3& velocity) = 0;
+
+    /**
+     * @brief Get the number of rigid bodies in the simulation.
+     *
+     * @return Body count
+     */
+    virtual size_t GetBodyCount() const = 0;
+
+    /**
+     * @brief Clear all rigid bodies from the simulation.
+     */
+    virtual void Clear() = 0;
+};
+
+}  // namespace sdl3cpp::services
diff --git a/src/services/interfaces/i_scene_service.hpp b/src/services/interfaces/i_scene_service.hpp
new file mode 100644
index 0000000..506f83d
--- /dev/null
+++ b/src/services/interfaces/i_scene_service.hpp
@@ -0,0 +1,58 @@
+#pragma once
+
+#include "i_graphics_service.hpp"
+#include "i_script_service.hpp"
+#include <vector>
+
+namespace sdl3cpp::services {
+
+/**
+ * @brief Scene management service interface.
+ *
+ * Maintains the scene graph and generates render commands for the graphics service.
+ * Separated from script service to decouple scene state from Lua execution.
+ */
+class ISceneService {
+public:
+    virtual ~ISceneService() = default;
+
+    /**
+     * @brief Load a scene from scene objects.
+     *
+     * Replaces the current scene with new objects.
+     *
+     * @param objects Vector of scene objects to load
+     */
+    virtual void LoadScene(const std::vector<SceneObject>& objects) = 0;
+
+    /**
+     * @brief Update scene state (animations, transformations, etc.).
+     *
+     * @param deltaTime Time since last update in seconds
+     */
+    virtual void UpdateScene(float deltaTime) = 0;
+
+    /**
+     * @brief Generate render commands for the current scene.
+     *
+     * Evaluates model matrices and prepares draw calls.
+     *
+     * @param time Current time in seconds
+     * @return Vector of render commands for the graphics service
+     */
+    virtual std::vector<RenderCommand> GetRenderCommands(float time) const = 0;
+
+    /**
+     * @brief Clear the scene (remove all objects).
+     */
+    virtual void Clear() = 0;
+
+    /**
+     * @brief Get the number of objects in the scene.
+     *
+     * @return Object count
+     */
+    virtual size_t GetObjectCount() const = 0;
+};
+
+}  // namespace sdl3cpp::services
diff --git a/src/services/interfaces/i_script_service.hpp b/src/services/interfaces/i_script_service.hpp
new file mode 100644
index 0000000..df036e0
--- /dev/null
+++ b/src/services/interfaces/i_script_service.hpp
@@ -0,0 +1,126 @@
+#pragma once
+
+#include "../../core/vertex.hpp"
+#include "i_graphics_service.hpp"
+#include <array>
+#include <cstdint>
+#include <filesystem>
+#include <string>
+#include <unordered_map>
+#include <vector>
+
+namespace sdl3cpp::services {
+
+/**
+ * @brief Scene object data structure.
+ */
+struct SceneObject {
+    std::string id;
+    std::vector<core::Vertex> vertices;
+    std::vector<uint16_t> indices;
+    std::string shaderKey;
+    int modelMatrixFuncRef;  // Lua function reference
+};
+
+/**
+ * @brief GUI input snapshot for Lua.
+ */
+struct GuiInputSnapshot {
+    float mouseX;
+    float mouseY;
+    float mouseWheelDelta;
+    bool mouseLeftPressed;
+    bool mouseRightPressed;
+    std::string textInput;
+};
+
+// Forward declare GUI types (defined in script/gui_types.hpp)
+struct GuiCommand;
+
+/**
+ * @brief Script service interface (Lua integration).
+ *
+ * Provides a clean API for Lua script execution and data exchange.
+ * Wraps the ScriptEngine and its internal managers (SceneManager,
+ * ShaderManager, GuiManager, AudioManager).
+ */
+class IScriptService {
+public:
+    virtual ~IScriptService() = default;
+
+    /**
+     * @brief Load and execute a Lua script.
+     *
+     * @param path Path to the Lua script file
+     * @param debug Whether to enable Lua debug mode
+     * @throws std::runtime_error if script loading fails
+     */
+    virtual void LoadScript(const std::filesystem::path& path, bool debug) = 0;
+
+    /**
+     * @brief Load scene objects from Lua.
+     *
+     * Calls the Lua function that generates the scene graph.
+     *
+     * @return Vector of scene objects with geometry and metadata
+     */
+    virtual std::vector<SceneObject> LoadSceneObjects() = 0;
+
+    /**
+     * @brief Compute model matrix for an object using Lua function.
+     *
+     * @param funcRef Lua function reference (from SceneObject)
+     * @param time Current time in seconds
+     * @return 4x4 model transformation matrix (column-major)
+     */
+    virtual std::array<float, 16> ComputeModelMatrix(int funcRef, float time) = 0;
+
+    /**
+     * @brief Get view-projection matrix from Lua.
+     *
+     * @param aspect Window aspect ratio (width/height)
+     * @return 4x4 view-projection matrix (column-major)
+     */
+    virtual std::array<float, 16> GetViewProjectionMatrix(float aspect) = 0;
+
+    /**
+     * @brief Load shader paths from Lua configuration.
+     *
+     * @return Map of shader key to shader file paths
+     */
+    virtual std::unordered_map<std::string, ShaderPaths> LoadShaderPaths() = 0;
+
+    /**
+     * @brief Update GUI input state in Lua.
+     *
+     * Sends current input state to Lua for GUI processing.
+     *
+     * @param input Input snapshot for this frame
+     */
+    virtual void UpdateGuiInput(const GuiInputSnapshot& input) = 0;
+
+    /**
+     * @brief Get GUI rendering commands from Lua.
+     *
+     * Retrieves the list of GUI commands generated by Lua scripts.
+     *
+     * @return Vector of GUI commands to render
+     */
+    virtual std::vector<GuiCommand> GetGuiCommands() = 0;
+
+    /**
+     * @brief Check if there are pending GUI commands.
+     *
+     * @return true if GUI commands are available, false otherwise
+     */
+    virtual bool HasGuiCommands() const = 0;
+
+    /**
+     * @brief Update physics simulation (calls Lua if needed).
+     *
+     * @param deltaTime Time since last update in seconds
+     */
+    virtual void UpdatePhysics(float deltaTime) = 0;
+};
+
+}  // namespace sdl3cpp::services
diff --git a/src/services/interfaces/i_shader_service.hpp b/src/services/interfaces/i_shader_service.hpp
new file mode 100644
index 0000000..3682b03
--- /dev/null
+++ b/src/services/interfaces/i_shader_service.hpp
@@ -0,0 +1,72 @@
+#pragma once
+
+#include "i_graphics_service.hpp"
+#include <string>
+#include <unordered_map>
+#include <vulkan/vulkan.h>
+
+namespace sdl3cpp::services {
+
+/**
+ * @brief Shader management service interface.
+ *
+ * Handles shader compilation, pipeline creation, and shader program management.
+ * Wraps the ShaderManager from the script module.
+ */
+class IShaderService {
+public:
+    virtual ~IShaderService() = default;
+
+    /**
+     * @brief Register a shader program.
+     *
+     * @param key Unique identifier for this shader program
+     * @param paths Vertex and fragment shader file paths
+     * @throws std::runtime_error if shader files don't exist
+     */
+    virtual void RegisterShader(const std::string& key, const ShaderPaths& paths) = 0;
+
+    /**
+     * @brief Compile all registered shaders and create pipelines.
+     *
+     * Must be called after all shaders are registered and before rendering.
+     *
+     * @throws std::runtime_error if compilation fails
+     */
+    virtual void CompileAll() = 0;
+
+    /**
+     * @brief Get the Vulkan pipeline for a shader program.
+     *
+     * @param key Shader program identifier
+     * @return VkPipeline handle
+     * @throws std::out_of_range if shader key doesn't exist
+     */
+    virtual VkPipeline GetPipeline(const std::string& key) const = 0;
+
+    /**
+     * @brief Check if a shader program exists.
+     *
+     * @param key Shader program identifier
+     * @return true if registered, false otherwise
+     */
+    virtual bool HasShader(const std::string& key) const = 0;
+
+    /**
+     * @brief Get the number of registered shader programs.
+     *
+     * @return Shader count
+     */
+    virtual size_t GetShaderCount() const = 0;
+
+    /**
+     * @brief Reload all shaders (for hot-reload support).
+     *
+     * Recompiles all shaders from their source files.
+     *
+     * @throws std::runtime_error if compilation fails
+     */
+    virtual void ReloadAll() = 0;
+};
+
+}  // namespace sdl3cpp::services
diff --git a/src/services/interfaces/i_window_service.hpp b/src/services/interfaces/i_window_service.hpp
new file mode 100644
index 0000000..318a771
--- /dev/null
+++ b/src/services/interfaces/i_window_service.hpp
@@ -0,0 +1,95 @@
+#pragma once
+
+#include <cstdint>
+#include <string>
+#include <utility>
+
+// Forward declare SDL types to avoid including SDL headers
+struct SDL_Window;
+
+namespace sdl3cpp::services {
+
+/**
+ * @brief Window configuration structure.
+ */
+struct WindowConfig {
+    uint32_t width;
+    uint32_t height;
+    std::string title;
+    bool resizable;
+};
+
+/**
+ * @brief Window management service interface.
+ *
+ * Handles SDL window creation, event polling, and window state management.
+ * Decouples SDL-specific details from the rest of the application.
+ */
+class IWindowService {
+public:
+    virtual ~IWindowService() = default;
+
+    /**
+     * @brief Create and show the application window.
+     *
+     * @param config Window configuration (size, title, flags)
+     * @throws std::runtime_error if window creation fails
+     */
+    virtual void CreateWindow(const WindowConfig& config) = 0;
+
+    /**
+     * @brief Destroy the window and release resources.
+     */
+    virtual void DestroyWindow() = 0;
+
+    /**
+     * @brief Get the native SDL window handle.
+     *
+     * Required for Vulkan surface creation and other low-level operations.
+     *
+     * @return Pointer to SDL_Window, or nullptr if no window exists
+     */
+    virtual SDL_Window* GetNativeHandle() const = 0;
+
+    /**
+     * @brief Get the current window size.
+     *
+     * @return Pair of (width, height) in pixels
+     */
+    virtual std::pair<uint32_t, uint32_t> GetSize() const = 0;
+
+    /**
+     * @brief Check if the window should close.
+     *
+     * Returns true when the user clicks the close button or
+     * a quit event is received.
+     *
+     * @return true if the application should exit, false otherwise
+     */
+    virtual bool ShouldClose() const = 0;
+
+    /**
+     * @brief Poll SDL events and publish them to the event bus.
+     *
+     * This should be called once per frame to process user input
+     * and window events. Events are converted to application events
+     * and published via the event bus.
+     */
+    virtual void PollEvents() = 0;
+
+    /**
+     * @brief Set the window title.
+     *
+     * @param title New window title
+     */
+    virtual void SetTitle(const std::string& title) = 0;
+
+    /**
+     * @brief Check if the window is minimized.
+     *
+     * @return true if minimized, false otherwise
+     */
+    virtual bool IsMinimized() const = 0;
+};
+
+}  // namespace sdl3cpp::services