diff --git a/src/kiwano/2d/Actor.h b/src/kiwano/2d/Actor.h
index 839add72..54067c75 100644
--- a/src/kiwano/2d/Actor.h
+++ b/src/kiwano/2d/Actor.h
@@ -502,6 +502,13 @@ public:
         return Property<Point, FlagUint8>(&transform_.skew, &dirty_flag_, DirtyFlag::DirtyTransform);
     }
 
+    /// \~chinese
+    /// @brief 获取Z轴顺序属性
+    inline Property<int, Function<void()>> ZOrderProperty()
+    {
+        return Property<int, Function<void()>>(&z_order_, Closure(this, &Actor::Reorder));
+    }
+
 protected:
     /// \~chinese
     /// @brief 更新自身和所有子角色
diff --git a/src/kiwano/2d/Sprite.cpp b/src/kiwano/2d/Sprite.cpp
index b06af6ce..5e643bd7 100644
--- a/src/kiwano/2d/Sprite.cpp
+++ b/src/kiwano/2d/Sprite.cpp
@@ -128,13 +128,25 @@ void Sprite::SetFrame(FramePtr frame, bool autoresize)
     if (frame_ != frame)
     {
         frame_ = frame;
-        if (frame_ && autoresize)
+        if (autoresize)
         {
-            SetSize(frame_->GetSize());
+            ResetSize();
         }
     }
 }
 
+void Sprite::ResetSize()
+{
+    if (frame_)
+    {
+        SetSize(frame_->GetSize());
+    }
+    else
+    {
+        SetSize(Size());
+    }
+}
+
 void Sprite::OnRender(RenderContext& ctx)
 {
     if (frame_ && frame_->IsValid())
diff --git a/src/kiwano/2d/Sprite.h b/src/kiwano/2d/Sprite.h
index f754d2f9..7ceebfb1 100644
--- a/src/kiwano/2d/Sprite.h
+++ b/src/kiwano/2d/Sprite.h
@@ -24,6 +24,7 @@
 
 namespace kiwano
 {
+
 KGE_DECLARE_SMART_PTR(Sprite);
 
 /**
@@ -112,6 +113,17 @@ public:
     /// @param autoresize 是否自动调整自身大小为图像大小
     void SetFrame(FramePtr frame, bool autoresize = true);
 
+    /// \~chinese
+    /// @brief 重置精灵大小为图像帧大小
+    void ResetSize();
+
+    /// \~chinese
+    /// @brief 获取图像帧属性
+    inline Property<FramePtr, Function<void()>> FrameProperty()
+    {
+        return Property<FramePtr, Function<void()>>(std::addressof(frame_), Closure(this, &Sprite::ResetSize));
+    }
+
     void OnRender(RenderContext& ctx) override;
 
 protected:
diff --git a/src/kiwano/core/Flag.h b/src/kiwano/core/Flag.h
index 731334b5..291fcb17 100644
--- a/src/kiwano/core/Flag.h
+++ b/src/kiwano/core/Flag.h
@@ -80,155 +80,4 @@ typedef Flag<int16_t>  FlagInt16;
 typedef Flag<int32_t>  FlagInt32;
 typedef Flag<int64_t>  FlagInt64;
 
-namespace bits
-{
-
-template <>
-inline void Set<FlagUint8>(FlagUint8& old, FlagUint8 flag)
-{
-    old.Set(flag.value);
-}
-
-template <>
-inline void Set<FlagUint16>(FlagUint16& old, FlagUint16 flag)
-{
-    old.Set(flag.value);
-}
-
-template <>
-inline void Set<FlagUint32>(FlagUint32& old, FlagUint32 flag)
-{
-    old.Set(flag.value);
-}
-
-template <>
-inline void Set<FlagUint64>(FlagUint64& old, FlagUint64 flag)
-{
-    old.Set(flag.value);
-}
-
-template <>
-inline void Set<FlagInt8>(FlagInt8& old, FlagInt8 flag)
-{
-    old.Set(flag.value);
-}
-
-template <>
-inline void Set<FlagInt16>(FlagInt16& old, FlagInt16 flag)
-{
-    old.Set(flag.value);
-}
-
-template <>
-inline void Set<FlagInt32>(FlagInt32& old, FlagInt32 flag)
-{
-    old.Set(flag.value);
-}
-
-template <>
-inline void Set<FlagInt64>(FlagInt64& old, FlagInt64 flag)
-{
-    old.Set(flag.value);
-}
-
-
-template <>
-inline void Unset<FlagUint8>(FlagUint8& old, FlagUint8 flag)
-{
-    old.Unset(flag.value);
-}
-
-template <>
-inline void Unset<FlagUint16>(FlagUint16& old, FlagUint16 flag)
-{
-    old.Unset(flag.value);
-}
-
-template <>
-inline void Unset<FlagUint32>(FlagUint32& old, FlagUint32 flag)
-{
-    old.Unset(flag.value);
-}
-
-template <>
-inline void Unset<FlagUint64>(FlagUint64& old, FlagUint64 flag)
-{
-    old.Unset(flag.value);
-}
-
-template <>
-inline void Unset<FlagInt8>(FlagInt8& old, FlagInt8 flag)
-{
-    old.Unset(flag.value);
-}
-
-template <>
-inline void Unset<FlagInt16>(FlagInt16& old, FlagInt16 flag)
-{
-    old.Unset(flag.value);
-}
-
-template <>
-inline void Unset<FlagInt32>(FlagInt32& old, FlagInt32 flag)
-{
-    old.Unset(flag.value);
-}
-
-template <>
-inline void Unset<FlagInt64>(FlagInt64& old, FlagInt64 flag)
-{
-    old.Unset(flag.value);
-}
-
-
-template <>
-inline bool Has<FlagUint8>(FlagUint8 old, FlagUint8 flag)
-{
-    return old.Has(flag.value);
-}
-
-template <>
-inline bool Has<FlagUint16>(FlagUint16 old, FlagUint16 flag)
-{
-    return old.Has(flag.value);
-}
-
-template <>
-inline bool Has<FlagUint32>(FlagUint32 old, FlagUint32 flag)
-{
-    return old.Has(flag.value);
-}
-
-template <>
-inline bool Has<FlagUint64>(FlagUint64 old, FlagUint64 flag)
-{
-    return old.Has(flag.value);
-}
-
-template <>
-inline bool Has<FlagInt8>(FlagInt8 old, FlagInt8 flag)
-{
-    return old.Has(flag.value);
-}
-
-template <>
-inline bool Has<FlagInt16>(FlagInt16 old, FlagInt16 flag)
-{
-    return old.Has(flag.value);
-}
-
-template <>
-inline bool Has<FlagInt32>(FlagInt32 old, FlagInt32 flag)
-{
-    return old.Has(flag.value);
-}
-
-template <>
-inline bool Has<FlagInt64>(FlagInt64 old, FlagInt64 flag)
-{
-    return old.Has(flag.value);
-}
-
-
-}  // namespace bits
 }  // namespace kiwano
diff --git a/src/kiwano/core/Property.h b/src/kiwano/core/Property.h
index bffc126b..e426cd3f 100644
--- a/src/kiwano/core/Property.h
+++ b/src/kiwano/core/Property.h
@@ -21,6 +21,7 @@
 #pragma once
 #include <kiwano/core/BitOperator.h>
 #include <kiwano/core/Flag.h>
+#include <kiwano/core/Function.h>
 
 namespace kiwano
 {
@@ -33,7 +34,8 @@ template <typename _Ty>
 class Property<_Ty, void>
 {
 public:
-    typedef _Ty value_type;
+    typedef _Ty  value_type;
+    typedef void notifier_type;
 
     inline Property(_Ty* ptr)
         : ptr_(ptr)
@@ -55,20 +57,83 @@ private:
 };
 
 
+template <typename _Ty, typename _FlagTy>
+class Property<_Ty, Flag<_FlagTy>>
+{
+public:
+    typedef _Ty           value_type;
+    typedef Flag<_FlagTy> notifier_type;
+
+    inline Property(_Ty* ptr, Flag<_FlagTy>* flag, _FlagTy flag_value)
+        : ptr_(ptr)
+        , flag_(flag)
+        , flag_value_(flag_value)
+    {
+    }
+
+    inline _Ty Get() const
+    {
+        return *ptr_;
+    }
+
+    inline void Set(const _Ty& value)
+    {
+        *ptr_ = value;
+        if (flag_)
+        {
+            flag_->Set(flag_value_);
+        }
+    }
+
+private:
+    _Ty*           ptr_;
+    Flag<_FlagTy>* flag_;
+    _FlagTy        flag_value_;
+};
+
+
+template <typename _Ty>
+class Property<_Ty, Function<void()>>
+{
+public:
+    typedef _Ty              value_type;
+    typedef Function<void()> notifier_type;
+
+    inline Property(_Ty* ptr, const Function<void()>& notifier)
+        : ptr_(ptr)
+        , notifier_(notifier)
+    {
+    }
+
+    inline _Ty Get() const
+    {
+        return *ptr_;
+    }
+
+    inline void Set(const _Ty& value)
+    {
+        *ptr_ = value;
+        if (notifier_)
+        {
+            notifier_();
+        }
+    }
+
+private:
+    _Ty*             ptr_;
+    Function<void()> notifier_;
+};
+
+
 template <typename _Ty, typename _NotifierTy>
 class Property
 {
 public:
+    static_assert(std::is_arithmetic<_NotifierTy>::value, "_NotifierTy must be an arithmetic type");
+
     typedef _Ty         value_type;
     typedef _NotifierTy notifier_type;
 
-    inline Property(_Ty* ptr)
-        : ptr_(ptr)
-        , notifier_(nullptr)
-        , notify_value_()
-    {
-    }
-
     inline Property(_Ty* ptr, _NotifierTy* notifier, _NotifierTy notify_value)
         : ptr_(ptr)
         , notifier_(notifier)