diff --git a/main.c b/main.c
index 4baddfb..8945162 100644
--- a/main.c
+++ b/main.c
@@ -98,7 +98,7 @@ struct _rect
     int invalid;
 
     // super
-    struct _shape shape;
+    struct _shape *shape;
     // struct _shape;
     // struct _virtual_table vtb;
 
@@ -110,20 +110,49 @@ struct _rect
     // void (*draw)(void *self);
 };
 
-double rect_area(struct _rect *self, void *parent)
+double rect_area(void *self, void *parent)
 {
-    double area = self->width * self->height;
+    double area = 0;
+    struct _rect *pthis = (struct _rect *)parent;
+    area = pthis->shape->vtb.area(self, NULL);
+    return area;
+}
+
+void rect_draw(void *self, void *parent)
+{
+    printf("rect draw\n");
+}
+
+double _rect_area(void *self, void *parent)
+{
+    struct _rect *pthis = (struct _rect *)self;
+    double area = pthis->width * pthis->height;
+
     printf("rect area = %0.2f\n", area);
     return area;
 }
 
-void rect_draw(struct _rect *self, void *parent)
+void _rect_draw(void *self, void *parent)
 {
     printf("rect draw\n");
 }
 
 struct _rect *rect_new(double width, double height)
 {
+    // super
+    static struct _virtual_table vtb = {
+        .area = (double (*)(void *self, void *parent))_rect_area,
+        .draw = (void (*)(void *self, void *parent))_rect_draw,
+    };
+
+    struct _shape *shape = shape_new();
+    if (shape == NULL)
+    {
+        return NULL;
+    }
+    shape->vtb = vtb;
+
+    // self
     struct _rect *rect = calloc(1, sizeof(struct _rect));
     if (rect == NULL)
     {
@@ -131,14 +160,9 @@ struct _rect *rect_new(double width, double height)
     }
     rect->width = width;
     rect->height = height;
+    // set parent
+    rect->shape = shape;
 
-    static struct _virtual_table vtb = {
-        .area = (double (*)(void *self, void *parent))rect_area,
-        .draw = (void (*)(void *self, void *parent))rect_draw
-    };
-
-    rect->shape.vtb = vtb;
-    // rect->vtb = vtb;
     return rect;
 }
 
@@ -147,9 +171,7 @@ struct _circle
     int invalid;
 
     // super
-    struct _shape shape;
-    // struct _shape;
-    // struct _virtual_table vtb;
+    struct _shape *shape;
 
     // attribute
     double radius;
@@ -172,26 +194,35 @@ void circle_draw(struct _circle *self, void *parent)
 
 struct _circle *circle_new(double radius)
 {
+    // super
+    static struct _virtual_table vtb = {
+        .area = (double (*)(void *self, void *parent))circle_area,
+        .draw = (void (*)(void *self, void *parent))circle_draw,
+    };
+
+    struct _shape *shape = shape_new();
+    if (shape == NULL)
+    {
+        return NULL;
+    }
+    shape->vtb = vtb;
+
+    // self
     struct _circle *circle = calloc(1, sizeof(struct _circle));
     if (circle == NULL)
     {
         return NULL;
     }
     circle->radius = radius;
+    // set parent
+    circle->shape = shape;
 
-    static struct _virtual_table vtb = {
-        .area = (double (*)(void *self, void *parent))circle_area,
-        .draw = (void (*)(void *self, void *parent))circle_draw,
-    };
-
-    // circle->vtb = vtb;
-    circle->shape.vtb = vtb;
     return circle;
 }
 
 struct _copper_cash
 {
-    struct _shape shape;
+    struct _shape *shape;
     struct _rect *rect;
     struct _circle *circle;
 
@@ -200,8 +231,8 @@ struct _copper_cash
 
 double copper_cash_area(struct _copper_cash *self, void *parent)
 {
-    double circle_area = self->circle->shape.vtb.area(self->circle, self->circle);
-    double rect_area = self->rect->shape.vtb.area(self->rect, self->rect);
+    double circle_area = self->circle->shape->vtb.area(self->circle, self->circle);
+    double rect_area = self->rect->shape->vtb.area(self->rect, self->rect);
     double area = circle_area - rect_area;
 
     printf("copper cash area = %0.2f\n", circle_area - rect_area);
@@ -216,32 +247,42 @@ void copper_cash_draw(struct _copper_cash *self, void *parent)
 
 struct _copper_cash *copper_cash_new(double width, double height, double radius)
 {
-    struct _copper_cash *cc = calloc(1, sizeof(struct _copper_cash));
-    if (cc == NULL)
+    // super
+    static struct _virtual_table vtb = {
+        .area = (double (*)(void *self, void *parent))copper_cash_area,
+        .draw = (void (*)(void *self, void *parent))copper_cash_draw,
+    };
+
+    struct _shape *shape = shape_new();
+    if (shape == NULL)
     {
         return NULL;
     }
+    shape->vtb = vtb;
 
     struct _rect *rect = rect_new(width, height);
     if(rect == NULL)
     {
         return NULL;
     }
-    cc->rect = rect;
 
     struct _circle *circle = circle_new(radius);
     if (circle == NULL)
     {
         return NULL;
     }
-    cc->circle = circle;
-    cc->price = 100;
 
-    static struct _virtual_table vtb = {
-        .area = (double (*)(void *self, void *parent))copper_cash_area,
-        .draw = (void (*)(void *self, void *parent))copper_cash_draw,
-    };
-    cc->shape.vtb = vtb;
+    // self
+    struct _copper_cash *cc = calloc(1, sizeof(struct _copper_cash));
+    if (cc == NULL)
+    {
+        return NULL;
+    }
+    cc->price = 100;
+    // set parent
+    cc->shape = shape;
+    cc->rect = rect;
+    cc->circle = circle;
     return cc;
 }
 
@@ -256,20 +297,20 @@ int main(int argc, char *argv[])
     circle_draw(circle, circle);
 
     printf("----- rect & circle -----\n");
-    shape_area(rect, &rect->shape);
-    shape_draw(rect, &rect->shape);
+    shape_area(rect, rect->shape);
+    shape_draw(rect, rect->shape);
 
-    shape_area(circle, &circle->shape);
-    shape_draw(circle, &circle->shape);
+    shape_area(circle, circle->shape);
+    shape_draw(circle, circle->shape);
 
     printf("----- [2] rect & circle -----\n");
     struct _rect *rect2 = (struct _rect *)rect_new(2, 3);
-    shape_area(rect2, &rect2->shape);
-    shape_draw(rect2, &rect2->shape);
+    shape_area(rect2, rect2->shape);
+    shape_draw(rect2, rect2->shape);
 
     struct _circle *circle2 = (struct _circle *)circle_new(1);
-    shape_area(circle2, &circle->shape);
-    shape_draw(circle2, &circle->shape);
+    shape_area(circle2, circle->shape);
+    shape_draw(circle2, circle->shape);
 
     // printf("----- [2] shape -----\n");
     // struct _shape *shape = shape_new();
@@ -278,8 +319,11 @@ int main(int argc, char *argv[])
 
     printf("----- copper_cash -----\n");
     struct _copper_cash *cc = copper_cash_new(2, 2, 4);
-    shape_area(cc, &cc->shape);
-    shape_draw(cc, &cc->shape);
+    shape_area(cc, cc->shape);
+    shape_draw(cc, cc->shape);
+
+    printf("----- [2] copper_cash -----\n");
+    rect_area(cc, cc->rect);
 
     return 0;
 }