diff --git a/src/game/vehicle.cpp b/src/game/vehicle.cpp
index deefaba..3d36b2d 100644
--- a/src/game/vehicle.cpp
+++ b/src/game/vehicle.cpp
@@ -101,6 +101,8 @@ void game::Vehicle::Update()
     ProcessInput();
     UpdateWheels();
 
+    sync_current_ = 1 - sync_current_;
+    UpdateSyncState();
     SendUpdateMsg();
 }
 
@@ -109,7 +111,12 @@ void game::Vehicle::SendInitData(Player& player, net::OutMessage& msg) const
     net::ModelName name(model_name_);
     msg.Write(name);
     net::WriteRGB(msg, color_); // primary color
-    WriteState(msg);
+
+    // write state against default
+    static const VehicleSyncState default_state;
+    size_t fields_pos = msg.Reserve<VehicleSyncFieldFlags>();
+    auto fields = WriteState(msg, default_state);
+    msg.WriteAt(fields_pos, fields);
 }
 
 void game::Vehicle::SetInput(VehicleInputType type, bool enable)
@@ -120,6 +127,12 @@ void game::Vehicle::SetInput(VehicleInputType type, bool enable)
         in_ &= ~(1 << type);
 }
 
+glm::vec3 game::Vehicle::GetPosition() const
+{
+    btVector3 pos = body_->getWorldTransform().getOrigin();
+    return glm::vec3(pos.x(), pos.y(), pos.z());
+}
+
 void game::Vehicle::SetPosition(const glm::vec3& pos)
 {
     auto t = body_->getWorldTransform();
@@ -240,25 +253,102 @@ void game::Vehicle::UpdateWheels()
     }
 }
 
-void game::Vehicle::WriteState(net::OutMessage& msg) const
+void game::Vehicle::UpdateSyncState()
 {
-    msg.Write(flags_);
-    net::WriteTransform(msg, root_.local);
+    VehicleSyncState& state = sync_[sync_current_];
 
-    // send wheel info
-    // msg.Write<uint8_t>(static_cast<uint8_t>(numwheels));
-    msg.Write<net::AngleQ>(steering_);
+    state.flags = flags_;
+    
+    net::EncodePosition(root_.local.position, state.pos);
+    net::EncodeRotation(root_.local.rotation, state.rot);
+
+    state.steering.Encode(steering_);
 
     for (size_t i = 0; i < num_wheels_; ++i)
     {
         auto& wheel = wheels_[i];
-        msg.Write<net::WheelZOffsetQ>(wheel.z_offset);
-        msg.Write<net::RotationSpeedQ>(wheel.speed);
+        state.wheels[i].z_offset.Encode(wheel.z_offset);
+        state.wheels[i].speed.Encode(wheel.speed);
     }
 }
 
+game::VehicleSyncFieldFlags game::Vehicle::WriteState(net::OutMessage& msg, const VehicleSyncState& base) const
+{
+    VehicleSyncFieldFlags fields = 0;
+    const VehicleSyncState& curr = sync_[sync_current_];
+
+    if (curr.flags != base.flags)
+    {
+        fields |= VSF_FLAGS;
+        msg.Write(curr.flags);
+    }
+
+    if (curr.pos.x.value != base.pos.x.value ||
+        curr.pos.y.value != base.pos.y.value ||
+        curr.pos.z.value != base.pos.z.value)
+    {
+        fields |= VSF_POSITION;
+
+        net::WriteDelta(msg, curr.pos.x, base.pos.x);
+        net::WriteDelta(msg, curr.pos.y, base.pos.y);
+        net::WriteDelta(msg, curr.pos.z, base.pos.z);
+    }
+
+    if (curr.rot.x.value != base.rot.x.value ||
+        curr.rot.y.value != base.rot.y.value ||
+        curr.rot.z.value != base.rot.z.value)
+    {
+        fields |= VSF_ROTATION;
+
+        net::WriteDelta(msg, curr.rot.x, base.rot.x);
+        net::WriteDelta(msg, curr.rot.y, base.rot.y);
+        net::WriteDelta(msg, curr.rot.z, base.rot.z);
+    }
+
+    if (curr.steering.value != base.steering.value)
+    {
+        fields |= VSF_STEERING;
+
+        net::WriteDelta(msg, curr.steering, base.steering);
+    }
+
+    bool wheels_changed = false;
+    for (size_t i = 0; i < num_wheels_; ++i)
+    {
+        if (curr.wheels[i].z_offset.value != base.wheels[i].z_offset.value ||
+            curr.wheels[i].speed.value != base.wheels[i].speed.value)
+        {
+            wheels_changed = true;
+            break;
+        }
+    }
+
+    if (wheels_changed)
+    {
+        fields |= VSF_WHEELS;
+
+        for (size_t i = 0; i < num_wheels_; ++i)
+        {
+            net::WriteDelta(msg, curr.wheels[i].z_offset, base.wheels[i].z_offset);
+            net::WriteDelta(msg, curr.wheels[i].speed, base.wheels[i].speed);
+        }
+    }
+
+    return fields;
+}
+
 void game::Vehicle::SendUpdateMsg()
 {
     auto msg = BeginEntMsg(net::EMSG_UPDATE);
-    WriteState(msg);
+    auto fields_pos = msg.Reserve<VehicleSyncFieldFlags>();
+    auto fields = WriteState(msg, sync_[1 - sync_current_]);
+
+    // TODO: allow this
+    // if (fields == 0)
+    // {
+    //     DiscardMsg();
+    //     return;
+    // }
+
+    msg.WriteAt(fields_pos, fields);
 }
diff --git a/src/game/vehicle.hpp b/src/game/vehicle.hpp
index 6ef8211..f0b8260 100644
--- a/src/game/vehicle.hpp
+++ b/src/game/vehicle.hpp
@@ -7,13 +7,11 @@
 #include "collision/motionstate.hpp"
 #include "entity.hpp"
 #include "world.hpp"
-#include "vehicleflags.hpp"
+#include "vehicle_sync.hpp"
 
 namespace game
 {
 
-static constexpr size_t MAX_WHEELS = 4;
-
 struct VehicleWheelState
 {
     float rotation = 0.0f; // [rad]
@@ -44,6 +42,7 @@ public:
 
     void SetInput(VehicleInputType type, bool enable);
 
+    glm::vec3 GetPosition() const;
     void SetPosition(const glm::vec3& pos);
 
     virtual ~Vehicle();
@@ -51,7 +50,8 @@ public:
 private:
     void ProcessInput();
     void UpdateWheels();
-    void WriteState(net::OutMessage& msg) const;
+    void UpdateSyncState();
+    VehicleSyncFieldFlags WriteState(net::OutMessage& msg, const VehicleSyncState& base) const;
     void SendUpdateMsg();
 
 private:
@@ -69,7 +69,9 @@ private:
     size_t num_wheels_ = 0;
     std::array<VehicleWheelState, MAX_WHEELS> wheels_;
 
-    VehicleFlags flags_;
+    VehicleFlags flags_ = VF_NONE;
+    VehicleSyncState sync_[2];
+    size_t sync_current_ = 0;
 
     VehicleInputFlags in_ = 0;
 };
diff --git a/src/game/vehicle_sync.hpp b/src/game/vehicle_sync.hpp
new file mode 100644
index 0000000..ff14018
--- /dev/null
+++ b/src/game/vehicle_sync.hpp
@@ -0,0 +1,49 @@
+#pragma once
+
+#include <cstdint>
+
+#include "net/defs.hpp"
+
+namespace game
+{
+
+constexpr size_t MAX_WHEELS = 4;
+
+using VehicleFlags = uint8_t;
+
+enum VehicleFlag : VehicleFlags
+{
+    VF_NONE,
+    VF_ACCELERATING = 1,
+    VF_BREAKING = 2,
+};
+
+struct VehicleSyncState
+{
+    VehicleFlags flags = VF_NONE;
+    
+    net::PositionQ pos;
+    net::QuatQ rot;
+
+    net::AngleQ steering;
+
+    struct
+    {
+        net::WheelZOffsetQ z_offset; // how much compressed
+        net::RotationSpeedQ speed;   // rad/s
+    } wheels[MAX_WHEELS];
+};
+
+using VehicleSyncFieldFlags = uint8_t;
+
+enum VehicleSyncFieldFlag
+{
+    VSF_FLAGS = 0x01,
+    VSF_POSITION = 0x02,
+    VSF_ROTATION = 0x04,
+    VSF_STEERING = 0x08,
+    VSF_WHEELS = 0x10,
+};
+
+
+} // namespace game
\ No newline at end of file
diff --git a/src/game/vehicleflags.hpp b/src/game/vehicleflags.hpp
deleted file mode 100644
index e292011..0000000
--- a/src/game/vehicleflags.hpp
+++ /dev/null
@@ -1,17 +0,0 @@
-#pragma once
-
-#include <cstdint>
-
-namespace game
-{
-
-using VehicleFlags = uint8_t;
-
-enum VehicleFlag : VehicleFlags
-{
-    VF_NONE,
-    VF_ACCELERATING = 1,
-    VF_BREAKING = 2,
-};
-
-}
\ No newline at end of file
diff --git a/src/gameview/vehicleview.cpp b/src/gameview/vehicleview.cpp
index 61d9245..2f4f41f 100644
--- a/src/gameview/vehicleview.cpp
+++ b/src/gameview/vehicleview.cpp
@@ -20,6 +20,11 @@ game::view::VehicleView::VehicleView(WorldView& world, std::shared_ptr<const ass
     color_ = glm::vec4(color, 1.0f);
 
     snd_accel_ = assets::CacheManager::GetSound("data/auto.snd");
+
+    // sync state
+    net::DecodePosition(sync_.pos, root_.local.position);
+    net::DecodeRotation(sync_.rot, root_.local.rotation);
+
 }
 
 std::unique_ptr<game::view::VehicleView> game::view::VehicleView::InitFromMsg(WorldView& world, net::InMessage& msg)
@@ -32,7 +37,9 @@ std::unique_ptr<game::view::VehicleView> game::view::VehicleView::InitFromMsg(Wo
     auto model = assets::CacheManager::GetVehicleModel("data/" + std::string(modelname) + ".veh");
 
     auto vehicle = std::make_unique<VehicleView>(world, std::move(model), color);
-    vehicle->ReadState(msg);
+    if (!vehicle->ReadState(msg))
+        return nullptr;
+
     vehicle->root_trans_[0] = vehicle->root_trans_[1];
 
     return vehicle;
@@ -135,27 +142,73 @@ bool game::view::VehicleView::ReadState(net::InMessage& msg)
     auto& root_trans = root_trans_[1];
     update_time_ = world_.GetTime();
 
-    if (!msg.Read(flags_))
+    // parse state delta
+    VehicleSyncFieldFlags fields;
+    if (!msg.Read(fields))
         return false;
 
-    if (!net::ReadTransform(msg, root_trans))
-        return false;
+    // flags
+    if (fields & VSF_FLAGS)
+    {
+        if (!msg.Read(flags_))
+            return false;
+    }
 
-    float steering;
-    if (!msg.Read<net::AngleQ>(steering))
-        return false;
+    // pos
+    if (fields & VSF_POSITION)
+    {
+        if (!net::ReadDelta(msg, sync_.pos.x) ||
+            !net::ReadDelta(msg, sync_.pos.y) ||
+            !net::ReadDelta(msg, sync_.pos.z))
+            return false;
+
+        net::DecodePosition(sync_.pos, root_trans.position);
+    }
+
+    // rot
+    if (fields & VSF_ROTATION)
+    {
+        if (!net::ReadDelta(msg, sync_.rot.x) ||
+            !net::ReadDelta(msg, sync_.rot.y) ||
+            !net::ReadDelta(msg, sync_.rot.z))
+            return false;
+
+        net::DecodeRotation(sync_.rot, root_trans.rotation);
+    }
+
+    // steering
+    if (fields & VSF_STEERING)
+    {
+        if (!net::ReadDelta(msg, sync_.steering))
+            return false;
+
+    }
+        
+    float steering = sync_.steering.Decode();
+
+    // wheels
+    if (fields & VSF_WHEELS)
+    {
+        for (size_t i = 0; i < wheels_.size(); ++i)
+        {
+            if (!net::ReadDelta(msg, sync_.wheels[i].z_offset) ||
+                !net::ReadDelta(msg, sync_.wheels[i].speed))
+                return false;
+        }
+    }
 
     const auto& wheels = model_->GetWheels();
     for (size_t i = 0; i < wheels_.size(); ++i)
     {
         auto& wheel = wheels_[i];
-        if (!msg.Read<net::WheelZOffsetQ>(wheel.z_offset) || !msg.Read<net::RotationSpeedQ>(wheel.speed))
-            return false;
+        wheel.z_offset = sync_.wheels[i].z_offset.Decode();
+        wheel.speed = sync_.wheels[i].speed.Decode();
 
         wheel.steering = i < 2 ? steering : 0.0f;
     }
 
-    return true;}
+    return true;
+}
 
 bool game::view::VehicleView::ProcessUpdateMsg(net::InMessage& msg)
 {
diff --git a/src/gameview/vehicleview.hpp b/src/gameview/vehicleview.hpp
index 6e39cc0..e64b93f 100644
--- a/src/gameview/vehicleview.hpp
+++ b/src/gameview/vehicleview.hpp
@@ -3,7 +3,7 @@
 #include "entityview.hpp"
 
 #include "assets/vehiclemdl.hpp"
-#include "game/vehicleflags.hpp"
+#include "game/vehicle_sync.hpp"
 
 #include <chrono>
 
@@ -38,6 +38,7 @@ private:
     std::shared_ptr<const assets::VehicleModel> model_;
     glm::vec4 color_;
 
+    game::VehicleSyncState sync_;
     std::vector<VehicleWheelViewInfo> wheels_;
 
     float update_time_ = 0.0f;
diff --git a/src/net/defs.hpp b/src/net/defs.hpp
index cd8b6d7..93df648 100644
--- a/src/net/defs.hpp
+++ b/src/net/defs.hpp
@@ -74,9 +74,19 @@ enum EntMsgType : uint8_t
     EMSG_UPDATE,
 };
 
-using PositionQ = Quantized<uint32_t, -10000, 10000, 1>;
+using PositionElemQ = Quantized<uint32_t, -10000, 10000, 1>;
+struct PositionQ
+{
+    PositionElemQ x, y, z;
+};
+
 using AngleQ = Quantized<uint16_t, -PI_N, PI_N, PI_D>;
-using QuatQ = Quantized<uint16_t, -1, 1, 1>;
+
+using QuatElemQ = Quantized<uint16_t, -1, 1, 1>;
+struct QuatQ
+{
+    QuatElemQ x, y, z;
+};
 
 using WheelZOffsetQ = Quantized<uint8_t, -1, 1, 1>;
 using RotationSpeedQ = Quantized<uint16_t, -300, 300, 1>;
diff --git a/src/net/msg_producer.cpp b/src/net/msg_producer.cpp
index aa0b16b..92d9358 100644
--- a/src/net/msg_producer.cpp
+++ b/src/net/msg_producer.cpp
@@ -9,8 +9,14 @@ void net::MsgProducer::ResetMsg()
 
 net::OutMessage net::MsgProducer::BeginMsg(net::MessageType type)
 {
+    msg_start_ = message_buf_.size();
     OutMessage msg(message_buf_);
     if (type != net::MSG_NONE)
         msg.Write(type);
     return msg;
 }
+
+void net::MsgProducer::DiscardMsg()
+{
+    message_buf_.resize(msg_start_);
+}
diff --git a/src/net/msg_producer.hpp b/src/net/msg_producer.hpp
index 4f9d2de..7eddece 100644
--- a/src/net/msg_producer.hpp
+++ b/src/net/msg_producer.hpp
@@ -15,10 +15,12 @@ public:
 
     void ResetMsg();
     OutMessage BeginMsg(MessageType type = MSG_NONE);
+    void DiscardMsg();
     std::span<const char> GetMsg() const { return message_buf_; };
 
 private:
     std::vector<char> message_buf_;
+    size_t msg_start_ = 0;
 };
 
 }
\ No newline at end of file
diff --git a/src/net/outmessage.hpp b/src/net/outmessage.hpp
index 29b49b4..6cd68e0 100644
--- a/src/net/outmessage.hpp
+++ b/src/net/outmessage.hpp
@@ -78,6 +78,12 @@ public:
         Write(q.value);
     }
 
+    // template <AnyQuantized T>
+    // void Write(T quant)
+    // {
+    //     Write(quant.value);
+    // }
+
     void WriteVarInt(int64_t value)
     {
         const bool negative = value < 0;
diff --git a/src/net/quantized.hpp b/src/net/quantized.hpp
index 01418a1..bb19e72 100644
--- a/src/net/quantized.hpp
+++ b/src/net/quantized.hpp
@@ -19,11 +19,11 @@ struct Quantized
     static constexpr float inv_scale = range / static_cast<float>(max_int);
 
 public:
-    T value;
+    T value{0};
 
     Quantized() = default;
     Quantized(T value) : value(value) {}
-    Quantized(float fvalue) { Encode(value); }
+    Quantized(float fvalue) { Encode(fvalue); }
 
     void Encode(float fvalue) noexcept
     {
diff --git a/src/net/utils.hpp b/src/net/utils.hpp
index 04bb61a..bfbf1c6 100644
--- a/src/net/utils.hpp
+++ b/src/net/utils.hpp
@@ -1,8 +1,8 @@
 #pragma once
 
 #include "defs.hpp"
-#include "outmessage.hpp"
 #include "inmessage.hpp"
+#include "outmessage.hpp"
 #include "utils/transform.hpp"
 
 namespace net
@@ -10,51 +10,107 @@ namespace net
 
 /// TRANSFORMS
 
-inline void WritePosition(OutMessage& msg, const glm::vec3& pos)
+// inline void WritePosition(OutMessage& msg, const glm::vec3& pos)
+// {
+//     msg.Write<PositionQ>(pos.x);
+//     msg.Write<PositionQ>(pos.y);
+//     msg.Write<PositionQ>(pos.z);
+// }
+
+inline void EncodePosition(const glm::vec3& pos, PositionQ& out)
 {
-    msg.Write<PositionQ>(pos.x);
-    msg.Write<PositionQ>(pos.y);
-    msg.Write<PositionQ>(pos.z);
+    out.x.Encode(pos.x);
+    out.y.Encode(pos.y);
+    out.z.Encode(pos.z);
 }
 
-inline void WriteRotation(OutMessage& msg, const glm::quat& quat)
+inline void WritePositionQ(OutMessage& msg, const PositionQ& posq)
+{
+    msg.Write(posq.x.value);
+    msg.Write(posq.y.value);
+    msg.Write(posq.z.value);
+}
+
+// inline void WriteRotation(OutMessage& msg, const glm::quat& quat)
+// {
+//     auto q = glm::normalize(quat);
+//     if (q.w < 0.0f)
+//         q = -q;
+
+//     msg.Write<QuatQ>(q.x);
+//     msg.Write<QuatQ>(q.y);
+//     msg.Write<QuatQ>(q.z);
+// }
+
+inline void EncodeRotation(const glm::quat& quat, QuatQ& out)
 {
     auto q = glm::normalize(quat);
     if (q.w < 0.0f)
         q = -q;
 
-    msg.Write<QuatQ>(q.x);
-    msg.Write<QuatQ>(q.y);
-    msg.Write<QuatQ>(q.z);
+    out.x.Encode(q.x);
+    out.y.Encode(q.y);
+    out.z.Encode(q.z);
 }
 
-inline void WriteTransform(OutMessage& msg, const Transform& trans)
+inline void WriteRotationQ(OutMessage& msg, const QuatQ& rotq)
 {
-    WritePosition(msg, trans.position);
-    WriteRotation(msg, trans.rotation);
+    msg.Write(rotq.x.value);
+    msg.Write(rotq.y.value);
+    msg.Write(rotq.z.value);
 }
 
-inline bool ReadPosition(InMessage& msg, glm::vec3& pos)
+// inline void WriteTransform(OutMessage& msg, const Transform& trans)
+// {
+//     WritePosition(msg, trans.position);
+//     WriteRotation(msg, trans.rotation);
+// }
+
+// inline bool ReadPosition(InMessage& msg, glm::vec3& pos)
+// {
+//     return msg.Read<PositionQ>(pos.x) && msg.Read<PositionQ>(pos.y) && msg.Read<PositionQ>(pos.z);
+// }
+
+inline bool ReadPositionQ(InMessage& msg, PositionQ& posq)
 {
-    return msg.Read<PositionQ>(pos.x) && msg.Read<PositionQ>(pos.y) && msg.Read<PositionQ>(pos.z);
+    return msg.Read(posq.x.value) && msg.Read(posq.y.value) && msg.Read(posq.z.value);
 }
 
-inline bool ReadRotation(InMessage& msg, glm::quat& q)
+inline void DecodePosition(const PositionQ& posq, glm::vec3& out)
 {
-    glm::vec3 v;
-    if (!msg.Read<QuatQ>(v.x) || !msg.Read<QuatQ>(v.y) || !msg.Read<QuatQ>(v.z))
-        return false;
+    out.x = posq.x.Decode();
+    out.y = posq.y.Decode();
+    out.z = posq.z.Decode();
+}
 
+// inline bool ReadRotation(InMessage& msg, glm::quat& q)
+// {
+//     glm::vec3 v;
+//     if (!msg.Read<QuatQ>(v.x) || !msg.Read<QuatQ>(v.y) || !msg.Read<QuatQ>(v.z))
+//         return false;
+
+//     float w = glm::sqrt(glm::max(0.0f, 1.0f - glm::dot(v, v)));
+//     q = glm::quat(w, v.x, v.y, v.z);
+
+//     return true;
+// }
+
+inline bool ReadRotationQ(InMessage& msg, QuatQ& rotq)
+{
+    return msg.Read(rotq.x.value) && msg.Read(rotq.y.value) && msg.Read(rotq.z.value);
+}
+
+inline void DecodeRotation(const QuatQ& rotq, glm::quat& out)
+{
+    glm::vec3 v(rotq.x.Decode(), rotq.y.Decode(), rotq.z.Decode());
     float w = glm::sqrt(glm::max(0.0f, 1.0f - glm::dot(v, v)));
-    q = glm::quat(w, v.x, v.y, v.z);
-
-    return true;
+    out = glm::quat(w, v.x, v.y, v.z);
 }
 
-inline bool ReadTransform(InMessage& msg, Transform& trans)
-{
-    return ReadPosition(msg, trans.position) && ReadRotation(msg, trans.rotation);
-}
+// inline bool ReadTransform(InMessage& msg, Transform& trans)
+// {
+//     return ReadPosition(msg, trans.position) && ReadRotation(msg, trans.rotation);
+// }
 
 /// COLOR
 
@@ -70,4 +126,50 @@ inline bool ReadRGB(InMessage& msg, glm::vec3& color)
     return msg.Read<ColorQ>(color.r) && msg.Read<ColorQ>(color.g) && msg.Read<ColorQ>(color.b);
 }
 
-}
\ No newline at end of file
+// DELTA
+template <std::unsigned_integral T>
+inline void WriteDelta(OutMessage& msg, T previous, T current)
+{
+    static_assert(sizeof(T) <= 4);
+
+    int64_t delta = static_cast<int64_t>(current) - static_cast<int64_t>(previous);
+
+    constexpr int64_t wrap = 1LL << (sizeof(T) * 8);
+    delta = (delta + wrap / 2) % wrap - wrap / 2;
+
+    msg.WriteVarInt(delta);
+}
+
+template <AnyQuantized T>
+inline void WriteDelta(OutMessage& msg, T current, T previous)
+{
+    WriteDelta(msg, previous.value, current.value);
+}
+
+template <std::unsigned_integral T>
+inline bool ReadDelta(InMessage& msg, T previous, T& current)
+{
+    static_assert(sizeof(T) <= 4);
+
+    int64_t encoded;
+    if (!msg.ReadVarInt(encoded))
+        return false;
+
+    constexpr uint64_t mask = (1ULL << (sizeof(T) * 8)) - 1;
+    current = static_cast<T>((static_cast<uint64_t>(previous) + static_cast<uint64_t>(encoded)) & mask);
+    return true;
+}
+
+template <std::unsigned_integral T>
+inline bool ReadDelta(InMessage& msg, T& value)
+{
+    return ReadDelta<T>(msg, value, value);
+}
+
+template <AnyQuantized T>
+inline bool ReadDelta(InMessage& msg, T& quant)
+{
+    return ReadDelta(msg, quant.value, quant.value);
+}
+
+} // namespace net
\ No newline at end of file