diff --git a/main.c b/main.c
index 1ae8b88..6c15aab 100644
--- a/main.c
+++ b/main.c
@@ -41,19 +41,19 @@ struct _virtual_table *virtual_new(void)
 
 struct _shape
 {
-    struct _virtual_table *vtb;
+    struct _virtual_table vtb;
 };
 
 void shape_area(void *self)
 {
     struct _shape *pthis = (struct _shape *)self;
-    pthis->vtb->area(self);
+    pthis->vtb.area(self);
 }
 
 void shape_draw(void *self)
 {
     struct _shape *pthis = (struct _shape *)self;
-    pthis->vtb->draw(self);
+    pthis->vtb.draw(self);
 }
 
 PRIVATE void _shape_area(void *self)
@@ -77,12 +77,10 @@ struct _shape *shape_new(void)
         .area = (void (*)(void *self))_shape_area, 
         .draw = (void (*)(void *self))_shape_draw
     };
-    shape->vtb = &vtb;
+    shape->vtb = vtb;
     return shape;
 }
 
-#define SUPER(self) (&(self)->shape)
-
 #if 0
 void shape_free(struct _shape * self)
 {
@@ -96,7 +94,8 @@ void shape_free(struct _shape * self)
 struct _rect
 {
     // super
-    struct _shape shape;
+    // struct _shape shape;
+    struct _virtual_table vtb;
 
     // attribute
     double width, height;
@@ -131,14 +130,15 @@ struct _rect *rect_new(double width, double height)
         .draw = (void (*)(void *self))rect_draw
     };
 
-    SUPER(rect)->vtb = &vtb;
+    rect->vtb = vtb;
     return rect;
 }
 
 struct _circle
 {
     // super
-    struct _shape shape;
+    // struct _shape shape;
+    struct _virtual_table vtb;
 
     // attribute
     double radius;
@@ -171,7 +171,7 @@ struct _circle *circle_new(double radius)
         .draw = (void (*)(void *self))circle_draw,
     };
 
-    SUPER(circle)->vtb = &vtb;
+    circle->vtb = vtb;
     return circle;
 }