diff --git a/library/common.h b/library/common.h
index 152bf32..a734e10 100644
--- a/library/common.h
+++ b/library/common.h
@@ -7,7 +7,6 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <assert.h>
-#include <stdarg.h>
 
 // [warring] offsetof is redefined in stddef.h
 // 
diff --git a/library/rect.c b/library/rect.c
index b6790e7..5b896d3 100644
--- a/library/rect.c
+++ b/library/rect.c
@@ -4,7 +4,8 @@
 double rect_area(void *self)
 {
     double area = 0;
-    struct _rect *pthis = container_of(self, struct _rect, me);
+    struct _rect *pthis = *(struct _rect **)self;
+    // struct _rect *pthis = container_of(self, struct _rect, me);
     area = pthis->shape->vtb.area(pthis);
     return area;
 }
diff --git a/library/shape.c b/library/shape.c
index 7cbc702..c21a95f 100644
--- a/library/shape.c
+++ b/library/shape.c
@@ -23,13 +23,20 @@ struct _virtual_table *virtual_new(void)
     return vtb;
 }
 
-
+#include "rect.h"
 
 double shape_area(void *self)
 {
     double area = 0;
-    struct _shape *pthis = container_of(self, struct _shape, me);
-    area = pthis->vtb.area(pthis);
+    struct _shape *parent = (*(struct _rect **)self)->shape;
+    area = parent->vtb.area(self);
+
+    // struct _shape *parent = *(struct _shape **)self;
+    // void * pthis = container_of(self, struct _rect, shape);
+    // area = parent->vtb.area(pthis);
+
+    // struct _rect *pthis = (struct _rect *)parent;
+    // pthis->shape->vtb.draw(self, NULL);
     return area;
 }
 
diff --git a/src/main.c b/src/main.c
index 413f5b9..011e59d 100644
--- a/src/main.c
+++ b/src/main.c
@@ -7,7 +7,7 @@
 int main(int argc, char *argv[])
 {
     struct _rect *rect = rect_new(4, 5);
-    rect_area(rect);
+    rect_area(&rect);
     rect_draw(rect);
 
     struct _circle *circle = circle_new(2);
@@ -15,7 +15,9 @@ int main(int argc, char *argv[])
     circle_draw(circle);
 
     printf("----- rect & circle -----\n");
-    shape_area(rect->shape);
+    // shape_area(rect);
+
+    shape_area(&rect);
     shape_draw(rect->shape);
 
     shape_area(circle->shape);