diff --git a/include/td/Maths.h b/include/td/Maths.h
index c5cad53..023ea6d 100644
--- a/include/td/Maths.h
+++ b/include/td/Maths.h
@@ -176,6 +176,11 @@ Mat4f Look(const Vec3f& eye, const Vec3f& center, const Vec3f& up);
 
 Mat4f Inverse(const Mat4f& mat);
 
+template<typename T>
+T Lerp(T v0, T v1, T t) {
+	return (T(1) - t) * v0 + t * v1;
+}
+
 }  // namespace maths
 
 
diff --git a/include/td/game/Mobs.h b/include/td/game/Mobs.h
index 9f24e5f..43ad263 100644
--- a/include/td/game/Mobs.h
+++ b/include/td/game/Mobs.h
@@ -9,6 +9,10 @@
 #include <memory>
 #include <vector>
 
+#include <sp/protocol/ConcreteMessage.h>
+#include <sp/common/GenericHandler.h>
+#include <sp/protocol/MessageFactory.h>
+
 namespace td {
 using Vec2fp = Vec2<FpFloat>;
 
@@ -65,152 +69,33 @@ const MobStats* GetMobStats(MobType type, std::uint8_t level);
 const TowerImmunities& GetMobTowerImmunities(MobType type, std::uint8_t level);
 const EffectImmunities& GetMobEffectImmunities(MobType type, std::uint8_t level);
 
-class Mob {
-  protected:
-	float m_Health;
+class MobHandler;
 
-  private:
-	Vec2fp m_Position;
+struct MobData {};
+
+class Mob : public sp::MessageBase<MobType, MobHandler> {
+  public:
 	MobID m_ID;
-	PlayerID m_Sender;
 	MobLevel m_Level;
+	PlayerID m_Sender;
+	float m_Health;
+	Vec2fp m_Position;
 	Direction m_Direction;
 	std::vector<EffectDuration> m_Effects;
 	const Tower* m_LastDamage;	// the last tower that damaged the mob
 	float m_HitCooldown;
-
-	// utils::Timer m_EffectFireTimer;
-	// utils::Timer m_EffectPoisonTimer;
-	// utils::Timer m_EffectHealTimer;
-
 	TeamCastle* m_CastleTarget;
 	// utils::CooldownTimer m_AttackTimer;
 
-  public:
-	Mob(MobID id, MobLevel level, PlayerID sender) : m_Sender(sender), m_Level(level), m_HitCooldown(0), m_CastleTarget(nullptr) {}
+	MobPtr m_Next;
 
-	virtual ~Mob() {}
+	Mob() {}
 
-	virtual MobType GetType() const = 0;
-
-	virtual bool OnDeath(World* world) {
-		return true;
-	}
-
-	Vec2fp& GetPosition() {
-		return m_Position;
-	}
-
-	MobID GetMobID() const {
-		return m_ID;
-	}
-	const TowerImmunities& GetTowerImmunities() const {
-		return GetMobTowerImmunities(GetType(), m_Level);
-	}
-	const EffectImmunities& GetEffectImmunities() const {
-		return GetMobEffectImmunities(GetType(), m_Level);
-	}
-	PlayerID GetSender() const {
-		return m_Sender;
-	}
-	MobLevel GetLevel() const {
-		return m_Level;
-	}
-	const MobStats* GetStats() const {
-		return GetMobStats(GetType(), m_Level);
-	}
-	void SetHealth(float newHealth) {
-		m_Health = newHealth;
-	}
-	float GetHealth() const {
-		return m_Health;
-	}
-	bool IsDead() const {
-		return m_Health <= 0;
-	}
-	bool IsAlive() const {
-		return m_Health > 0;
-	}
-	const Tower* GetLastDamageTower() {
-		return m_LastDamage;
-	}
-	bool HasReachedEnemyCastle() {
-		return m_CastleTarget != nullptr;
-	}
-
-	void Damage(float dmg, const Tower* damager) {
-		m_Health = std::max(0.0f, m_Health - dmg);
-		m_LastDamage = damager;
-		m_HitCooldown = 0.1;
-	}
-
-	void Heal(float heal) {
-		m_Health = std::min(static_cast<float>(GetStats()->m_MaxLife), m_Health + heal);
-	}
-
-	void SetMobReachedCastle(TeamCastle* castle) {
-		m_CastleTarget = castle;
-	}  // used when mob is in front of the castle
-
-	bool IsImmuneTo(TowerType type);
-
-	bool IsImmuneTo(EffectType type);
-	void AddEffect(EffectType type, float durationSec, Tower* tower);
-	bool HasEffect(EffectType type);
-
-	bool HasTakenDamage() {
-		return m_HitCooldown > 0;
-	}
-
-	// // returns a float between 0 and 1 excluded
-	// float GetTileX() {
-	// 	return GetCenterX() - static_cast<float>(static_cast<std::int32_t>(GetCenterX()));
-	// }
-
-	// // returns a float between 0 and 1 excluded
-	// float GetTileY() {
-	// 	return GetCenterY() - static_cast<float>(static_cast<std::int32_t>(GetCenterY()));
-	// }
-
-	Direction GetDirection() const {
-		return m_Direction;
-	}
-	void SetDirection(Direction dir) {
-		m_Direction = dir;
-	}
-
-  protected:
-	void InitMob() {
-		m_Health = static_cast<float>(GetStats()->m_MaxLife);
-		// SetSize(GetStats()->m_Size.x, GetStats()->m_Size.y);
-	}
-
-  private:
-	void UpdateEffects(std::uint64_t delta, World* world);
-	void AttackCastle(std::uint64_t delta, World* world);
-	void Move(std::uint64_t delta, World* world);
-	void Walk(std::uint64_t delta, World* world);
-	void MoveBack(const TeamCastle& castle, World* world);
-	void ChangeDirection(const WalkableTile& tile, World* world);
-	bool IsTouchingCastle(const TeamCastle& castle) const;
-	EffectDuration& GetEffect(EffectType type);
+	Mob& operator=(const Mob& a_Other) = default;
 };
 
-typedef std::shared_ptr<Mob> MobPtr;
-
-template <MobType MT>
-class ConcreteMob : public Mob {
-  public:
-	ConcreteMob(MobID id, std::uint8_t level, PlayerID sender) : Mob(id, level, sender) {
-		InitMob();
-	}
-
-	virtual ~ConcreteMob() {}
-
-	virtual constexpr MobType GetType() const override {
-		return MT;
-	}
-};
+template <MobType ID>
+using ConcreteMob = sp::ConcreteMessage<MobData, Mob, ID>;
 
 using Zombie = ConcreteMob<MobType::Zombie>;
 using Spider = ConcreteMob<MobType::Spider>;
@@ -223,16 +108,17 @@ using Witch = ConcreteMob<MobType::Witch>;
 using Slime = ConcreteMob<MobType::Slime>;
 using Giant = ConcreteMob<MobType::Giant>;
 
-namespace MobFactory {
+using AllMobs = std::tuple<Zombie, Spider, Skeleton, PigMan, Creeper, Silverfish, Blaze, Witch, Slime, Giant>;
 
-MobPtr CreateMob(MobID id, MobType type, std::uint8_t level, PlayerID sender);
-std::string GetMobName(MobType type);
+class MobHandler : public sp::GenericHandler<AllMobs> {};
 
-}  // namespace MobFactory
+using MobFactory = sp::MessageFactory<Mob, AllMobs>;
 
 class MobListener {
   public:
-	virtual void OnMobSpawn(Mob* mob) {}
+	virtual void OnMobSpawn(Mob* mob) {
+		MobHandler h;
+	}
 	virtual void OnMobDie(Mob* mob) {}
 
 	virtual void OnMobDamage(Mob* target, float damage, Tower* damager) {}
diff --git a/include/td/game/World.h b/include/td/game/World.h
index da2b1f7..410a04c 100644
--- a/include/td/game/World.h
+++ b/include/td/game/World.h
@@ -21,6 +21,7 @@ class World {
 	TilePalette m_TilePalette;
 
 	sim::WorldSnapshot m_CurrentState;
+	sim::WorldSnapshot m_NextState;
 
   private:
 	sim::WorldTicker m_Ticker;
diff --git a/include/td/protocol/command/Commands.h b/include/td/protocol/command/Commands.h
index 87f5c4e..a0dcdbb 100644
--- a/include/td/protocol/command/Commands.h
+++ b/include/td/protocol/command/Commands.h
@@ -9,7 +9,7 @@
 #include <sp/protocol/ConcreteMessage.h>
 #include <sp/protocol/MessageDispatcher.h>
 #include <sp/protocol/MessageFactory.h>
-#include <sp/protocol/MessageHandler.h>
+#include <sp/common/GenericHandler.h>
 #include <td/Types.h>
 #include <td/common/NonCopyable.h>
 #include <td/protocol/command/CommandData.h>
@@ -33,7 +33,7 @@ class CommandHandler;
 using CommandBase = sp::MessageBase<CommandID, CommandHandler>;
 
 template <typename TData, CommandID ID>
-using CommandMessage = sp::ConcreteMessage<TData, CommandID, ID, CommandHandler>;
+using CommandMessage = sp::ConcreteMessage<TData, CommandBase, ID>;
 
 
 namespace commands {
@@ -51,7 +51,7 @@ using UseItemCommand = CommandMessage<cdata::UseItem, CommandID::UseItem>;
 using AllCommands = std::tuple<commands::EndCommand, commands::PlaceTowerCommand, commands::PlayerJoinCommand,
 	commands::SpawnTroopCommand, commands::TeamChangeCommand, commands::UpgradeTowerCommand, commands::UseItemCommand>;
 
-class CommandHandler : public sp::MessageHandler<AllCommands> {};
+class CommandHandler : public sp::GenericHandler<AllCommands> {};
 
 using CommandDispatcher = sp::MessageDispatcher<CommandBase>;
 
diff --git a/include/td/protocol/packet/Packets.h b/include/td/protocol/packet/Packets.h
index 4be3b2f..544061b 100644
--- a/include/td/protocol/packet/Packets.h
+++ b/include/td/protocol/packet/Packets.h
@@ -12,7 +12,7 @@
 #include <sp/protocol/MessageBase.h>
 #include <sp/protocol/MessageDispatcher.h>
 #include <sp/protocol/MessageFactory.h>
-#include <sp/protocol/MessageHandler.h>
+#include <sp/common/GenericHandler.h>
 
 namespace td {
 namespace protocol {
@@ -37,7 +37,7 @@ using PacketBase = sp::MessageBase<PacketID, PacketHandler>;
 
 
 template <typename TData, PacketID ID>
-using PacketMessage = sp::ConcreteMessage<TData, PacketID, ID, PacketHandler>;
+using PacketMessage = sp::ConcreteMessage<TData, PacketBase, ID>;
 
 
 namespace packets {
@@ -61,7 +61,7 @@ using AllPackets = std::tuple<packets::BeginGamePacket, packets::ChatMessagePack
 	packets::KeepAlivePacket, packets::LockStepsPacket, packets::LoggingSuccessPacket, packets::PlayerJoinPacket,
 	packets::PlayerLeavePacket, packets::PlayerLoginPacket, packets::WorldHeaderPacket, packets::WorldDataPacket>;
 
-class PacketHandler : public sp::MessageHandler<AllPackets> {};
+class PacketHandler : public sp::GenericHandler<AllPackets> {};
 
 using PacketDispatcher = sp::MessageDispatcher<PacketBase>;
 
diff --git a/include/td/render/Renderer.h b/include/td/render/Renderer.h
index fa25234..cb5c23b 100644
--- a/include/td/render/Renderer.h
+++ b/include/td/render/Renderer.h
@@ -10,7 +10,8 @@ namespace render {
 
 class BasicRenderer {
   public:
-	virtual void Render() = 0;
+	virtual void Render(float a_Lerp) = 0;
+	virtual ~BasicRenderer() {}
 
 	void Render(const GL::VertexArray& a_Vao);
 };
@@ -24,6 +25,11 @@ class Renderer : public BasicRenderer {
   public:
 	Renderer(Camera& a_Camera);
 	virtual ~Renderer() {}
+
+	template <typename T>
+	float Lerp(const T& a_Mob, float a_LerpFactor, const std::function<float(const T&)>& a_MemberGetter) {
+		return static_cast<float>(maths::Lerp(a_MemberGetter(a_Mob), a_MemberGetter(*a_Mob.m_Next), a_LerpFactor));
+	}
 };
 
 class RenderPipeline {
@@ -32,7 +38,7 @@ class RenderPipeline {
 
   public:
 	RenderPipeline();
-	~RenderPipeline() = default;
+	virtual ~RenderPipeline() {}
 
 	template <typename T, typename... Args>
 	void AddRenderer(Args&&... args) {
@@ -43,9 +49,9 @@ class RenderPipeline {
 		m_Renderers.clear();
 	}
 
-	void Render() {
+	void Render(float a_Lerp) {
 		for (auto& renderer : m_Renderers) {
-			renderer->Render();
+			renderer->Render(a_Lerp);
 		}
 	}
 };
diff --git a/include/td/render/renderer/EntityRenderer.h b/include/td/render/renderer/EntityRenderer.h
index 4f6562c..eefd91d 100644
--- a/include/td/render/renderer/EntityRenderer.h
+++ b/include/td/render/renderer/EntityRenderer.h
@@ -16,7 +16,7 @@ class EntityRenderer : public Renderer<shader::EntityShader> {
 	EntityRenderer(Camera& a_Camera, const game::World& a_World);
 	virtual ~EntityRenderer();
 
-	virtual void Render() override;
+	virtual void Render(float a_Lerp) override;
 };
 
 }  // namespace render
diff --git a/include/td/render/renderer/WorldRenderer.h b/include/td/render/renderer/WorldRenderer.h
index 93dfb8d..ded2b24 100644
--- a/include/td/render/renderer/WorldRenderer.h
+++ b/include/td/render/renderer/WorldRenderer.h
@@ -10,14 +10,13 @@ namespace render {
 
 class WorldRenderer : public Renderer<shader::WorldShader> {
   private:
-	const game::World& m_World;
 	std::unique_ptr<GL::VertexArray> m_WorldVao;
 
   public:
 	WorldRenderer(Camera& a_Camera, const game::World& a_World);
 	virtual ~WorldRenderer();
 
-	virtual void Render() override;
+	virtual void Render(float a_Lerp) override;
 };
 
 }  // namespace render
diff --git a/include/td/simulation/CommandApply.h b/include/td/simulation/CommandApply.h
index e98c217..b16dfe2 100644
--- a/include/td/simulation/CommandApply.h
+++ b/include/td/simulation/CommandApply.h
@@ -14,7 +14,7 @@ class CommandApply : public protocol::CommandHandler {
   public:
 	CommandApply(const game::World& a_World, WorldSnapshot& a_Snapshot);
 
-	virtual void Handle(const protocol::cdata::SpawnTroop& a_SpawnTroop) override;
+	virtual void Handle(const protocol::commands::SpawnTroopCommand& a_SpawnTroop) override;
 };
 
 }  // namespace sim
diff --git a/include/td/simulation/RealTimeSimulation.h b/include/td/simulation/RealTimeSimulation.h
index a97b03e..694f500 100644
--- a/include/td/simulation/RealTimeSimulation.h
+++ b/include/td/simulation/RealTimeSimulation.h
@@ -17,9 +17,18 @@ class RealTimeSimulation {
 	std::size_t m_CurrentStep;
 
   public:
+	/**
+	 * \param a_StepTime in ms
+	 */
 	RealTimeSimulation(game::World& a_World, GameHistory&& a_History, std::uint64_t a_StepTime);
 
-	void Update();
+	/**
+	 * \return the progress [0-1] between two steps
+	 */
+	float Update();
+
+  private:
+	void Step();
 };
 
 }  // namespace sim
diff --git a/include/td/simulation/WorldTicker.h b/include/td/simulation/WorldTicker.h
index 42555e3..9d6d838 100644
--- a/include/td/simulation/WorldTicker.h
+++ b/include/td/simulation/WorldTicker.h
@@ -23,12 +23,12 @@ class WorldTicker {
 	WorldTicker();
 
 	WorldSnapshot NextStep(
-		const game::World& a_World, const WorldSnapshot& a_PreviousState, const protocol::LockStep& a_LockStep, FpFloat a_Delta);
+		const game::World& a_World, WorldSnapshot& a_PreviousState, const protocol::LockStep& a_LockStep, FpFloat a_Delta);
 
   private:
 	void ApplySteps(const game::World& a_World, WorldSnapshot& a_State, const protocol::LockStep& a_LockStep);
 	void Tick(const game::World& a_World, WorldSnapshot& a_State, FpFloat a_Delta);
-	WorldSnapshot CreateNext(const WorldSnapshot& a_PreviousState);
+	WorldSnapshot CreateNext(WorldSnapshot& a_PreviousState);
 
 	template <typename T>
 	void AddSystem() {
diff --git a/src/main.cpp b/src/main.cpp
index 53f6b90..8b035d4 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -20,11 +20,11 @@ class WorldApply : public td::protocol::PacketHandler {
   public:
 	WorldApply(td::game::World& a_World) : m_World(a_World) {}
 
-	void Handle(const td::protocol::pdata::WorldHeader& a_Header) override {
-		m_World.LoadMap(a_Header);
+	void Handle(const td::protocol::packets::WorldHeaderPacket& a_Header) override {
+		m_World.LoadMap(*a_Header);
 	}
-	void Handle(const td::protocol::pdata::WorldData& a_Data) override {
-		m_World.LoadMap(a_Data);
+	void Handle(const td::protocol::packets::WorldDataPacket& a_Data) override {
+		m_World.LoadMap(*a_Data);
 	}
 };
 
@@ -93,15 +93,15 @@ int main(int argc, char** argv) {
 	renderer.AddRenderer<td::render::WorldRenderer>(cam, w);
 	renderer.AddRenderer<td::render::EntityRenderer>(cam, w);
 
-	cam.SetCamPos({77, 25, 13});
+	cam.SetCamPos({77, 5, 13});
 	cam.UpdatePerspective(display.GetAspectRatio());
 
-	td::sim::RealTimeSimulation simulation(w, std::move(gh), 1000);
+	td::sim::RealTimeSimulation simulation(w, std::move(gh), 2000);
 
 	while (!display.IsCloseRequested()) {
 		display.PollEvents();
-		simulation.Update();
-		renderer.Render();
+		float lerp = simulation.Update();
+		renderer.Render(lerp);
 		display.Update();
 	}
 
diff --git a/src/td/game/World.cpp b/src/td/game/World.cpp
index fefb18b..78c515a 100644
--- a/src/td/game/World.cpp
+++ b/src/td/game/World.cpp
@@ -5,9 +5,7 @@
 namespace td {
 namespace game {
 
-World::World() : m_CurrentState{.m_Teams{Team{TeamColor::Red}, Team{TeamColor::Blue}}} {
-	
-}
+World::World() : m_CurrentState{.m_Teams{Team{TeamColor::Red}, Team{TeamColor::Blue}}}, m_NextState{.m_Teams{Team{TeamColor::Red}, Team{TeamColor::Blue}}} {}
 
 const Color* World::GetTileColor(TilePtr tile) const {
 	switch (tile->GetType()) {
@@ -58,7 +56,8 @@ bool World::LoadMap(const protocol::pdata::WorldData& a_WorldData) {
 }
 
 void World::Tick(const protocol::LockStep& a_LockStep, FpFloat a_Delta) {
-	m_CurrentState = m_Ticker.NextStep(*this, m_CurrentState, a_LockStep, a_Delta);
+	m_CurrentState = m_NextState;
+	m_NextState = m_Ticker.NextStep(*this, m_NextState, a_LockStep, a_Delta);
 }
 
 }  // namespace game
diff --git a/src/td/render/renderer/EntityRenderer.cpp b/src/td/render/renderer/EntityRenderer.cpp
index 55eaa67..bdfa53b 100644
--- a/src/td/render/renderer/EntityRenderer.cpp
+++ b/src/td/render/renderer/EntityRenderer.cpp
@@ -13,16 +13,19 @@ EntityRenderer::EntityRenderer(Camera& a_Camera, const game::World& a_World) : R
 
 EntityRenderer::~EntityRenderer() {}
 
-void EntityRenderer::Render() {
+
+
+void EntityRenderer::Render(float a_Lerp) {
 	m_Shader->Start();
 	for (const auto& mob : m_World.GetMobList()) {
-		const auto mobCoords = mob->GetPosition();
-		float x = static_cast<float>(mobCoords.x);
-		float z = static_cast<float>(mobCoords.y);
+
+		float x = Lerp<game::Mob>(*mob, a_Lerp, [](const game::Mob& a_Mob) { return static_cast<float>(a_Mob.m_Position.x); });
+		float z = Lerp<game::Mob>(*mob, a_Lerp, [](const game::Mob& a_Mob) { return static_cast<float>(a_Mob.m_Position.y); });
+
 		m_Shader->SetModelPos({x, 1, z});
 		Renderer::Render(*m_EntityVao);
 	}
 }
 
-}	 // namespace render
+}  // namespace render
 }  // namespace td
diff --git a/src/td/render/renderer/WorldRenderer.cpp b/src/td/render/renderer/WorldRenderer.cpp
index 468aad3..078dc5d 100644
--- a/src/td/render/renderer/WorldRenderer.cpp
+++ b/src/td/render/renderer/WorldRenderer.cpp
@@ -7,13 +7,13 @@
 namespace td {
 namespace render {
 
-WorldRenderer::WorldRenderer(Camera& a_Camera, const game::World& a_World) : Renderer(a_Camera), m_World(a_World) {
-	m_WorldVao = std::make_unique<GL::VertexArray>(std::move(WorldLoader::LoadWorldModel(&a_World)));
+WorldRenderer::WorldRenderer(Camera& a_Camera, const game::World& a_World) : Renderer(a_Camera) {
+	m_WorldVao = std::make_unique<GL::VertexArray>(WorldLoader::LoadWorldModel(&a_World));
 }
 
 WorldRenderer::~WorldRenderer() {}
 
-void WorldRenderer::Render() {
+void WorldRenderer::Render(float a_Lerp) {
 	m_Shader->Start();
 	Renderer::Render(*m_WorldVao);
 	ImGui::ShowDemoWindow();
diff --git a/src/td/simulation/CommandApply.cpp b/src/td/simulation/CommandApply.cpp
index eeaa9e2..852ef6d 100644
--- a/src/td/simulation/CommandApply.cpp
+++ b/src/td/simulation/CommandApply.cpp
@@ -5,9 +5,9 @@ namespace sim {
 
 CommandApply::CommandApply(const game::World& a_World, WorldSnapshot& a_Snapshot) : m_World(a_World), m_Snapshot(a_Snapshot) {}
 
-void CommandApply::Handle(const protocol::cdata::SpawnTroop& a_SpawnTroop) {
-	auto zombie = std::make_shared<game::Zombie>(0, *a_SpawnTroop.m_Level, a_SpawnTroop.m_Sender);
-	zombie->GetPosition() = a_SpawnTroop.m_Position;
+void CommandApply::Handle(const protocol::commands::SpawnTroopCommand& a_SpawnTroop) {
+	auto zombie = std::make_shared<game::Zombie>();
+	zombie->m_Position = a_SpawnTroop->m_Position;
 	m_Snapshot.m_Mobs.push_back(zombie);
 }
 
diff --git a/src/td/simulation/RealTimeSimulation.cpp b/src/td/simulation/RealTimeSimulation.cpp
index 6abfc42..438c424 100644
--- a/src/td/simulation/RealTimeSimulation.cpp
+++ b/src/td/simulation/RealTimeSimulation.cpp
@@ -16,16 +16,24 @@ RealTimeSimulation::RealTimeSimulation(game::World& a_World, GameHistory&& a_His
 	m_History(std::move(a_History)),
 	m_CurrentTime(0),
 	m_LastTime(GetTime()),
-	m_CurrentStep(0) {}
+	m_CurrentStep(0) {
+	Step();
+}
 
-void RealTimeSimulation::Update() {
+float RealTimeSimulation::Update() {
+	// TODO: handle freezes (m_CurrentTime > 2 * m_StepTime)
 	m_CurrentTime += GetTime() - m_LastTime;
 	m_LastTime = GetTime();
 	if (m_CurrentTime > m_StepTime) {
-		m_World.Tick(m_History[m_CurrentStep], FpFloat(m_StepTime) / FpFloat(1000));
-		m_CurrentStep++;
+		Step();
 		m_CurrentTime -= m_StepTime;
 	}
+	return (float) m_CurrentTime / (float) m_StepTime;
+}
+
+void RealTimeSimulation::Step() {
+	m_World.Tick(m_History[m_CurrentStep], FpFloat(m_StepTime) / FpFloat(1000));
+	m_CurrentStep++;
 }
 
 }  // namespace sim
diff --git a/src/td/simulation/WorldTicker.cpp b/src/td/simulation/WorldTicker.cpp
index 367f90b..ae972a8 100644
--- a/src/td/simulation/WorldTicker.cpp
+++ b/src/td/simulation/WorldTicker.cpp
@@ -13,9 +13,9 @@ WorldTicker::WorldTicker() {
 }
 
 WorldSnapshot WorldTicker::NextStep(
-	const game::World& a_World, const WorldSnapshot& a_PreviousState, const protocol::LockStep& a_LockStep, FpFloat a_Delta) {
+	const game::World& a_World, WorldSnapshot& a_PreviousState, const protocol::LockStep& a_LockStep, FpFloat a_Delta) {
 	WorldSnapshot next = CreateNext(a_PreviousState);
-	ApplySteps(a_World, next, a_LockStep);
+	ApplySteps(a_World, next, a_LockStep); // maybe swap with tick ?
 	Tick(a_World, next, a_Delta);
 	return next;
 }
@@ -33,8 +33,21 @@ void WorldTicker::Tick(const game::World& a_World, WorldSnapshot& a_State, FpFlo
 	}
 }
 
-WorldSnapshot WorldTicker::CreateNext(const WorldSnapshot& a_PreviousState) {
-	return a_PreviousState;
+WorldSnapshot WorldTicker::CreateNext(WorldSnapshot& a_PreviousState) {
+	static game::MobFactory mobFactory;
+
+	WorldSnapshot next {
+		.m_Towers = a_PreviousState.m_Towers,
+		.m_Teams = a_PreviousState.m_Teams
+	};
+	next.m_Mobs.reserve(a_PreviousState.m_Mobs.size());
+	for (auto& mob : a_PreviousState.m_Mobs) {
+		game::MobPtr newMob = std::shared_ptr<game::Mob>(mobFactory.CreateMessage(mob->GetId()).release());
+		*newMob = *mob;
+		mob->m_Next = newMob;
+		next.m_Mobs.push_back(newMob);
+	}
+	return next;
 }
 
 }  // namespace sim
diff --git a/src/td/simulation/system/EntityMove.cpp b/src/td/simulation/system/EntityMove.cpp
index 4592762..798a6f8 100644
--- a/src/td/simulation/system/EntityMove.cpp
+++ b/src/td/simulation/system/EntityMove.cpp
@@ -5,7 +5,7 @@ namespace sim {
 
 void EntityMove::Tick(const game::World& a_World, WorldSnapshot& a_State, FpFloat a_Delta) {
 	for (auto& mob : a_State.m_Mobs) {
-		mob->GetPosition().x += a_Delta;
+		mob->m_Position.x += a_Delta;
 	}
 }