diff --git a/include/client/Client.h b/include/client/Client.h
index f1c18e8..836aea8 100644
--- a/include/client/Client.h
+++ b/include/client/Client.h
@@ -15,6 +15,8 @@ class Client : public StateMachine<Client, void, float> {
   public:
 	Client(const std::shared_ptr<IClientSocket>& a_Socket) : m_Socket(a_Socket) {}
 
+	void SendPacket(const protocol::PacketBase& a_Packet);
+
 	friend class ClientState;
 };
 
diff --git a/include/client/state/GameState.h b/include/client/state/GameState.h
index 3f484bf..b4fcacd 100644
--- a/include/client/state/GameState.h
+++ b/include/client/state/GameState.h
@@ -10,6 +10,7 @@ namespace client {
 class GameState : public ClientState {
   private:
 	std::shared_ptr<game::World> m_World;
+	// sim::ClientSimulation m_Simulation;
 
   public:
 	GameState(Client& a_Client, const std::shared_ptr<game::World>& a_World);
diff --git a/include/server/socket/FakeSocket.h b/include/server/socket/FakeSocket.h
index 8f14e94..3601cf4 100644
--- a/include/server/socket/FakeSocket.h
+++ b/include/server/socket/FakeSocket.h
@@ -9,7 +9,7 @@ namespace server {
 
 class FakeSocket : public IServerSocket {
   private:
-	std::vector<std::optional<std::shared_ptr<client::FakeSocket>>> m_Clients;
+	std::vector<std::optional<std::weak_ptr<client::FakeSocket>>> m_Clients;
 
   public:
 	FakeSocket() {}
diff --git a/include/td/common/StateMachine.h b/include/td/common/StateMachine.h
index c17a84a..f4adc8e 100644
--- a/include/td/common/StateMachine.h
+++ b/include/td/common/StateMachine.h
@@ -1,6 +1,7 @@
 #pragma once
 
 #include <memory>
+#include <cassert>
 
 namespace td {
 
@@ -19,16 +20,17 @@ class StateMachine {
 	};
 
 	StateMachine() {}
+	StateMachine(StateMachine&&) = default;
 	virtual ~StateMachine() {}
 
-	TReturn Update(TArgs... args) {
-		assert(m_State);
+	virtual TReturn Update(TArgs... args) {
+		assert(m_State && "You must change state at least once before updating !");
 		return m_State->Update(args...);
 	}
 
 	template <typename T, typename... Args>
 	void ChangeState(Args&&... args) {
-		m_State = std::make_unique<T>(static_cast<TDerived&>(*this), args...);
+		m_State = std::make_unique<T>(static_cast<TDerived&>(*this), std::forward<Args>(args)...);
 	}
 
   private:
diff --git a/include/td/input/Display.h b/include/td/display/Display.h
similarity index 82%
rename from include/td/input/Display.h
rename to include/td/display/Display.h
index 7d1bf87..8bc90aa 100644
--- a/include/td/input/Display.h
+++ b/include/td/display/Display.h
@@ -2,39 +2,14 @@
 
 #include <string>
 
-#include <SDL3/SDL_video.h>
 #include <SDL3/SDL_keycode.h>
+#include <SDL3/SDL_video.h>
+#include <td/common/StateMachine.h>
 #include <td/misc/Signal.h>
 
 namespace td {
 
-class Display {
-  public:
-	utils::Signal<float> OnAspectRatioChange;
-	utils::Signal<SDL_Keycode> OnKeyDown;
-
-	Display(int a_Width, int a_Height, const std::string& a_Title);
-	~Display();
-
-	void PollEvents();
-	void Update();
-
-	bool IsCloseRequested() {
-		return m_ShouldClose;
-	}
-
-	float GetAspectRatio() {
-		return m_AspectRatio;
-	}
-	
-	int GetWindowWidth() {
-		return m_LastWidth;
-	}
-
-	int GetWindowHeight() {
-		return m_LastHeight;
-	}
-
+class Display : public StateMachine<Display, void, float> {
   private:
 	SDL_Window* m_Window;
 	SDL_GLContext m_GLContext;
@@ -43,6 +18,33 @@ class Display {
 	float m_AspectRatio;
 
 	bool m_ShouldClose;
+
+  public:
+	utils::Signal<float> OnAspectRatioChange;
+	utils::Signal<SDL_Keycode> OnKeyDown;
+
+	Display(int a_Width, int a_Height, const std::string& a_Title);
+	~Display();
+
+	void PollEvents();
+	void Update(float a_Delta) override;
+	void Close();
+
+	bool IsCloseRequested() {
+		return m_ShouldClose;
+	}
+
+	float GetAspectRatio() {
+		return m_AspectRatio;
+	}
+
+	int GetWindowWidth() {
+		return m_LastWidth;
+	}
+
+	int GetWindowHeight() {
+		return m_LastHeight;
+	}
 };
 
 }  // namespace td
\ No newline at end of file
diff --git a/include/td/display/DisplayState.h b/include/td/display/DisplayState.h
new file mode 100644
index 0000000..0ad0790
--- /dev/null
+++ b/include/td/display/DisplayState.h
@@ -0,0 +1,16 @@
+#pragma once
+
+#include <td/display/Display.h>
+#include <td/misc/SlotGuard.h>
+
+namespace td {
+class DisplayState : public Display::State, private utils::SlotGuard {
+  public:
+	DisplayState(Display& a_Display);
+	virtual ~DisplayState() {}
+
+  protected:
+	virtual void OnAspectRatioChange(float a_Ratio) {}
+	virtual void OnKeyDown(SDL_Keycode a_Key) {}
+};
+}  // namespace td
diff --git a/include/td/display/state/DebugWorldState.h b/include/td/display/state/DebugWorldState.h
new file mode 100644
index 0000000..e9a1a64
--- /dev/null
+++ b/include/td/display/state/DebugWorldState.h
@@ -0,0 +1,33 @@
+#pragma once
+
+#include <client/Client.h>
+#include <server/Server.h>
+#include <td/display/DisplayState.h>
+#include <td/render/Renderer.h>
+#include <td/simulation/ClientSimulation.h>
+
+namespace td {
+
+class ClientHandler;
+
+class DebugWorldState : public DisplayState {
+  private:
+	render::RenderPipeline m_Renderer;
+	std::unique_ptr<client::Client> m_Client;
+	std::unique_ptr<server::Server> m_Server;
+	std::unique_ptr<sim::ClientSimulation> m_Simulation;
+	render::Camera m_Camera;
+	std::unique_ptr<ClientHandler> m_ClientHandler;
+
+  public:
+	DebugWorldState(Display& a_Display);
+	~DebugWorldState();
+
+	virtual void Update(float a_Delta) override;
+
+  protected:
+	virtual void OnAspectRatioChange(float a_Ratio) override;
+	virtual void OnKeyDown(SDL_Keycode a_Key) override;
+};
+
+}  // namespace td
diff --git a/src/client/Client.cpp b/src/client/Client.cpp
index 277b956..8c98606 100644
--- a/src/client/Client.cpp
+++ b/src/client/Client.cpp
@@ -3,7 +3,9 @@
 namespace td {
 namespace client {
 
-
+void Client::SendPacket(const protocol::PacketBase& a_Packet) {
+	m_Socket->Send(a_Packet);
+}
 
 }  // namespace client
 }  // namespace td
diff --git a/src/main.cpp b/src/main.cpp
index 5062e30..7850dcd 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -1,107 +1,5 @@
 #include <chrono>
-#include <fstream>
-#include <iostream>
-
-#include <td/game/World.h>
-#include <td/input/Display.h>
-#include <td/protocol/packet/PacketSerialize.h>
-#include <td/protocol/packet/Packets.h>
-#include <td/render/renderer/EntityRenderer.h>
-#include <td/render/renderer/TowerRenderer.h>
-#include <td/render/renderer/WorldRenderer.h>
-#include <td/simulation/ClientSimulation.h>
-
-#include <sp/common/DataBuffer.h>
-#include <sp/extensions/Compress.h>
-#include <sp/io/MessageStream.h>
-#include <sp/io/StdIo.h>
-
-#include <server/Server.h>
-#include <server/socket/FakeSocket.h>
-#include <server/state/GameState.h>
-
-#include <client/Client.h>
-#include <client/socket/FakeSocket.h>
-#include <client/state/GameState.h>
-
-class WorldApply : public td::protocol::PacketHandler {
-  private:
-	td::game::World& m_World;
-	using td::protocol::PacketHandler::Handle;
-
-  public:
-	WorldApply(td::game::World& a_World) : m_World(a_World) {}
-
-	void Handle(const td::protocol::packets::WorldHeaderPacket& a_Header) override {
-		m_World.LoadMap(*a_Header);
-	}
-
-	void Handle(const td::protocol::packets::WorldDataPacket& a_Data) override {
-		m_World.LoadMap(*a_Data);
-	}
-};
-
-class ClientHandler : public td::protocol::PacketHandler {
-  private:
-	td::sim::ClientSimulation& m_Simulation;
-
-	using td::protocol::PacketHandler::Handle;
-
-  public:
-	ClientHandler(td::sim::ClientSimulation& a_Simulation) : m_Simulation(a_Simulation) {}
-
-	void Handle(const td::protocol::packets::LockStepsPacket& a_LockStep) {
-		m_Simulation.Handle(a_LockStep);
-	}
-
-	void Handle(const td::protocol::packets::LockStepResponsePacket& a_LockStep) {
-		m_Simulation.Handle(a_LockStep);
-	}
-};
-
-void Save(const td::protocol::PacketBase& header, const td::protocol::PacketBase& data) {
-	auto comp = std::make_shared<sp::ZlibCompress>();
-
-	std::ofstream fStream("test/tdmap.tdmap3");
-	auto out = std::make_shared<sp::StdOuput>(fStream);
-
-	sp::MessageStream<td::protocol::PacketFactory> stream(std::move(out), std::move(comp));
-
-	stream.WriteMessage(header, false);
-	stream.WriteMessage(data, false);
-}
-
-td::game::WorldPtr GetWorld() {
-	auto comp = std::make_shared<sp::ZlibCompress>();
-
-	std::ifstream fStream("test/tdmap.tdmap2");
-	auto out = std::make_shared<sp::StdInput>(fStream);
-
-	sp::MessageStream<td::protocol::PacketFactory> stream(std::move(out), std::move(comp));
-
-	auto header = stream.ReadMessage(td::protocol::PacketID::WorldHeader);
-	auto data = stream.ReadMessage(td::protocol::PacketID::WorldData);
-
-	auto w = std::make_shared<td::game::World>();
-	auto wa = std::make_shared<WorldApply>(*w);
-
-	td::protocol::PacketDispatcher d;
-	d.RegisterHandler(wa);
-
-	d.Dispatch(*header);
-	d.Dispatch(*data);
-
-	Save(*header, *data);
-
-	return w;
-}
-
-void FastForward(td::game::World& a_World, const td::sim::GameHistory& a_LockSteps) {
-	const td::FpFloat delta = td::FpFloat(1) / td::FpFloat(75);
-	for (const auto& lockstep : a_LockSteps) {
-		a_World.Tick(lockstep, delta);
-	}
-}
+#include <td/display/state/DebugWorldState.h>
 
 float GetDelta() {
 	static std::chrono::time_point<std::chrono::system_clock> m_LastTime = std::chrono::system_clock::now();
@@ -112,65 +10,15 @@ float GetDelta() {
 }
 
 int main(int argc, char** argv) {
-	td::game::WorldPtr serverWorld = GetWorld();
-
-	// server
-	auto serverFakeSocket = std::make_shared<td::server::FakeSocket>();
-	td::server::Server server(serverFakeSocket);
-
-	// client
-	auto clientFakeSocket = td::client::FakeSocket::Connect(serverFakeSocket);
-	td::client::Client client(clientFakeSocket);
-
 	// init GL context
 	td::Display display(1920, 1080, "Tower-Defense 2");
 
-	td::render::Camera cam;
-
-	display.OnAspectRatioChange.Connect([&cam](float a_AspectRatio) { cam.UpdatePerspective(a_AspectRatio); });
-
-	td::game::WorldPtr clientWorld = GetWorld();
-
-	td::render::RenderPipeline renderer;
-	renderer.AddRenderer<td::render::WorldRenderer>(cam, *clientWorld);
-	renderer.AddRenderer<td::render::EntityRenderer>(cam, *clientWorld);
-	renderer.AddRenderer<td::render::TowerRenderer>(cam, *clientWorld);
-
-	cam.SetCamPos({77, 7, 13});
-	cam.UpdatePerspective(display.GetAspectRatio());
-
-	td::sim::ClientSimulation simulation(*clientWorld, td::STEP_TIME);
-	ClientHandler clientHandler(simulation);
-
-	// packets from the server to the client
-	clientFakeSocket->OnReceive.Connect([&clientHandler](const td::protocol::PacketBase& a_Packet) {
-		a_Packet.Dispatch(clientHandler);
-	});
-
-	simulation.OnMissingLockSteps.Connect([&clientFakeSocket](const std::vector<td::StepTime>& a_MissingSteps) {
-		clientFakeSocket->Send(td::protocol::packets::LockStepRequestPacket(a_MissingSteps));
-	});
-
-	// temporary tests
-	display.OnKeyDown.Connect([&clientFakeSocket](SDL_Keycode key) {
-		if (key == SDLK_A) {
-			clientFakeSocket->Send(td::protocol::packets::SpawnTroopPacket(td::EntityType::Zombie, 1));
-		} else if (key == SDLK_Z) {
-			clientFakeSocket->Send(td::protocol::packets::PlaceTowerPacket(td::TowerType::Archer, td::TowerCoords(77, 13)));
-		}
-	});
-
-	server.ChangeState<td::server::GameState>(serverWorld);
-	client.ChangeState<td::client::GameState>(clientWorld);
+	display.ChangeState<td::DebugWorldState>();
 
 	while (!display.IsCloseRequested()) {
 		display.PollEvents();
 		float delta = GetDelta();
-		server.Update(delta);
-		client.Update(delta);
-		float lerp = simulation.Update(delta);
-		renderer.Render(lerp);
-		display.Update();
+		display.Update(delta);
 	}
 
 	return 0;
diff --git a/src/server/socket/FakeSocket.cpp b/src/server/socket/FakeSocket.cpp
index 1b58cb7..f968bd4 100644
--- a/src/server/socket/FakeSocket.cpp
+++ b/src/server/socket/FakeSocket.cpp
@@ -6,7 +6,8 @@ namespace server {
 void FakeSocket::SendPeer(PeerID a_Peer, const protocol::PacketBase& a_Packet) {
 	auto socket = m_Clients.at(a_Peer);
 	assert(socket.has_value());
-	socket.value()->OnReceive(a_Packet);
+	assert(!socket.value().expired());
+	socket.value().lock()->OnReceive(a_Packet);
 }
 
 void FakeSocket::ReceiveFromFakePeer(PeerID a_Peer, const protocol::PacketBase& a_Packet) {
@@ -29,7 +30,8 @@ PeerID FakeSocket::ConnectFakePeer(const std::shared_ptr<client::FakeSocket>& a_
 void FakeSocket::DisconnectFakePeer(PeerID a_Peer) {
 	auto socket = m_Clients.at(a_Peer);
 	assert(socket.has_value());
-	socket.value()->OnDisconnect();
+	assert(!socket.value().expired());
+	socket.value().lock()->OnDisconnect();
 	OnDisconnectPeer(a_Peer);
 }
 
diff --git a/src/td/input/Display.cpp b/src/td/display/Display.cpp
similarity index 97%
rename from src/td/input/Display.cpp
rename to src/td/display/Display.cpp
index ec32934..88499b8 100644
--- a/src/td/input/Display.cpp
+++ b/src/td/display/Display.cpp
@@ -1,4 +1,4 @@
-#include <td/input/Display.h>
+#include <td/display/Display.h>
 
 #include <GL/glew.h>
 #include <SDL3/SDL.h>
@@ -125,6 +125,9 @@ Display::Display(int a_Width, int a_Height, const std::string& a_Title) :
 	ImGui_ImplOpenGL3_Init("#version 330");
 }
 
+void Display::Close() {
+	m_ShouldClose = true;
+}
 
 void Display::PollEvents() {
 	SDL_Event event;
@@ -161,7 +164,8 @@ void Display::PollEvents() {
 	ImGui::NewFrame();
 }
 
-void Display::Update() {
+void Display::Update(float a_Delta) {
+	StateMachine::Update(a_Delta);
 	ImGui::Render();
 	ImGuiIO& io = ImGui::GetIO();
 	glViewport(0, 0, (int)io.DisplaySize.x, (int)io.DisplaySize.y);
diff --git a/src/td/display/DisplayState.cpp b/src/td/display/DisplayState.cpp
new file mode 100644
index 0000000..c40e53a
--- /dev/null
+++ b/src/td/display/DisplayState.cpp
@@ -0,0 +1,10 @@
+#include <td/display/DisplayState.h>
+
+namespace td {
+
+DisplayState::DisplayState(Display& a_Display) : Display::State(a_Display) {
+	Connect(m_StateMachine.OnKeyDown, std::bind(&DisplayState::OnKeyDown, this, std::placeholders::_1));
+	Connect(m_StateMachine.OnAspectRatioChange, std::bind(&DisplayState::OnAspectRatioChange, this, std::placeholders::_1));
+}
+
+}  // namespace td
diff --git a/src/td/display/state/DebugWorldState.cpp b/src/td/display/state/DebugWorldState.cpp
new file mode 100644
index 0000000..559a7ab
--- /dev/null
+++ b/src/td/display/state/DebugWorldState.cpp
@@ -0,0 +1,162 @@
+#include <td/display/state/DebugWorldState.h>
+
+#include <chrono>
+#include <fstream>
+#include <iostream>
+
+#include <td/game/World.h>
+#include <td/protocol/packet/PacketSerialize.h>
+#include <td/protocol/packet/Packets.h>
+#include <td/render/renderer/EntityRenderer.h>
+#include <td/render/renderer/TowerRenderer.h>
+#include <td/render/renderer/WorldRenderer.h>
+#include <td/simulation/ClientSimulation.h>
+
+#include <sp/common/DataBuffer.h>
+#include <sp/extensions/Compress.h>
+#include <sp/io/MessageStream.h>
+#include <sp/io/StdIo.h>
+
+#include <server/Server.h>
+#include <server/socket/FakeSocket.h>
+#include <server/state/GameState.h>
+
+#include <client/Client.h>
+#include <client/socket/FakeSocket.h>
+#include <client/state/GameState.h>
+
+#include <td/display/Display.h>
+#include <td/display/state/DebugWorldState.h>
+
+namespace td {
+
+class ClientHandler : public protocol::PacketHandler {
+  private:
+	sim::ClientSimulation& m_Simulation;
+
+	using protocol::PacketHandler::Handle;
+
+  public:
+	ClientHandler(sim::ClientSimulation& a_Simulation) : m_Simulation(a_Simulation) {}
+
+	void Handle(const protocol::packets::LockStepsPacket& a_LockStep) {
+		m_Simulation.Handle(a_LockStep);
+	}
+
+	void Handle(const protocol::packets::LockStepResponsePacket& a_LockStep) {
+		m_Simulation.Handle(a_LockStep);
+	}
+};
+
+class WorldApply : public protocol::PacketHandler {
+  private:
+	game::World& m_World;
+	using protocol::PacketHandler::Handle;
+
+  public:
+	WorldApply(game::World& a_World) : m_World(a_World) {}
+
+	void Handle(const protocol::packets::WorldHeaderPacket& a_Header) override {
+		m_World.LoadMap(*a_Header);
+	}
+
+	void Handle(const protocol::packets::WorldDataPacket& a_Data) override {
+		m_World.LoadMap(*a_Data);
+	}
+};
+
+void Save(const protocol::PacketBase& header, const protocol::PacketBase& data) {
+	auto comp = std::make_shared<sp::ZlibCompress>();
+
+	std::ofstream fStream("test/tdmap.tdmap3");
+	auto out = std::make_shared<sp::StdOuput>(fStream);
+
+	sp::MessageStream<protocol::PacketFactory> stream(std::move(out), std::move(comp));
+
+	stream.WriteMessage(header, false);
+	stream.WriteMessage(data, false);
+}
+
+game::WorldPtr GetWorld() {
+	auto comp = std::make_shared<sp::ZlibCompress>();
+
+	std::ifstream fStream("test/tdmap.tdmap2");
+	auto out = std::make_shared<sp::StdInput>(fStream);
+
+	sp::MessageStream<protocol::PacketFactory> stream(std::move(out), std::move(comp));
+
+	auto header = stream.ReadMessage(protocol::PacketID::WorldHeader);
+	auto data = stream.ReadMessage(protocol::PacketID::WorldData);
+
+	auto w = std::make_shared<game::World>();
+	auto wa = std::make_shared<WorldApply>(*w);
+
+	protocol::PacketDispatcher d;
+	d.RegisterHandler(wa);
+
+	d.Dispatch(*header);
+	d.Dispatch(*data);
+
+	Save(*header, *data);
+
+	return w;
+}
+
+DebugWorldState::DebugWorldState(Display& a_Display) : DisplayState(a_Display) {
+	game::WorldPtr serverWorld = GetWorld();
+
+	// server
+	auto serverFakeSocket = std::make_shared<server::FakeSocket>();
+	m_Server = std::make_unique<server::Server>(serverFakeSocket);
+
+	// client
+	auto clientFakeSocket = client::FakeSocket::Connect(serverFakeSocket);
+	m_Client = std::make_unique<client::Client>(clientFakeSocket);
+
+	game::WorldPtr clientWorld = GetWorld();
+
+	m_Renderer.AddRenderer<render::WorldRenderer>(m_Camera, *clientWorld);
+	m_Renderer.AddRenderer<render::EntityRenderer>(m_Camera, *clientWorld);
+	m_Renderer.AddRenderer<render::TowerRenderer>(m_Camera, *clientWorld);
+
+	m_Camera.SetCamPos({77, 7, 13});
+	m_Camera.UpdatePerspective(m_StateMachine.GetAspectRatio());
+
+	m_Simulation = std::make_unique<sim::ClientSimulation>(*clientWorld, STEP_TIME);
+
+	m_ClientHandler = std::make_unique<ClientHandler>(*m_Simulation);
+
+	// packets from the server to the client
+	clientFakeSocket->OnReceive.Connect([this](const protocol::PacketBase& a_Packet) { a_Packet.Dispatch(*m_ClientHandler); });
+
+	m_Simulation->OnMissingLockSteps.Connect([clientFakeSocket](const std::vector<td::StepTime>& a_MissingSteps) {
+		clientFakeSocket->Send(protocol::packets::LockStepRequestPacket(a_MissingSteps));
+	});
+
+	m_Server->ChangeState<server::GameState>(serverWorld);
+	m_Client->ChangeState<client::GameState>(clientWorld);
+}
+
+void DebugWorldState::Update(float a_Delta) {
+	m_Server->Update(a_Delta);
+	m_Client->Update(a_Delta);
+	float lerp = m_Simulation->Update(a_Delta);
+	m_Renderer.Render(lerp);
+}
+
+void DebugWorldState::OnAspectRatioChange(float a_Ratio) {
+	m_Camera.UpdatePerspective(a_Ratio);
+}
+
+void DebugWorldState::OnKeyDown(SDL_Keycode a_Key) {
+	// temporary tests
+	if (a_Key == SDLK_A) {
+		m_Client->SendPacket(td::protocol::packets::SpawnTroopPacket(td::EntityType::Zombie, 1));
+	} else if (a_Key == SDLK_Z) {
+		m_Client->SendPacket(td::protocol::packets::PlaceTowerPacket(td::TowerType::Archer, td::TowerCoords(77, 13)));
+	}
+}
+
+DebugWorldState::~DebugWorldState() {}
+
+}  // namespace td