diff --git a/CMakelists.txt b/CMakelists.txt
index dfd6194..901ffd6 100644
--- a/CMakelists.txt
+++ b/CMakelists.txt
@@ -8,5 +8,7 @@ set(CMAKE_BUILD_TYPE "Debug")
 set(CMAKE_CXX_FLAGS_DEBUG "$ENV{CXXFLAGS} -O0 -Wall -g -ggdb")
 set(CMAKE_CXX_FLAGS_RELEASE "$ENV{CXXFLAGS} -O3 -Wall")
 
+include_directories(library)
+
 add_subdirectory(library)
 add_subdirectory(src)
diff --git a/library/circle.c b/library/circle.c
new file mode 100644
index 0000000..c4e4a62
--- /dev/null
+++ b/library/circle.c
@@ -0,0 +1,57 @@
+
+#include "circle.h"
+
+double circle_area(void *self, void *parent)
+{
+    double area = 0;
+    struct _circle *pthis = (struct _circle *)parent;
+    area = pthis->shape->vtb.area(self, NULL);
+    return area;
+}
+
+void circle_draw(void *self, void *parent)
+{
+    struct _circle *pthis = (struct _circle *)parent;
+    pthis->shape->vtb.draw(self, NULL);
+}
+
+double _circle_area(void *self, void *parent)
+{
+    struct _circle *pthis = (struct _circle *)self;
+    double area = 3.14 * pthis->radius * pthis->radius;
+    printf("circle area = %0.2f\n", area);
+    return area;
+}
+
+void _circle_draw(void *self,  void *parent)
+{
+    printf("circle draw\n");
+}
+
+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;
+
+    return circle;
+}
diff --git a/library/circle.h b/library/circle.h
new file mode 100644
index 0000000..263e059
--- /dev/null
+++ b/library/circle.h
@@ -0,0 +1,28 @@
+
+#ifndef _CIRCLE_H_
+#define _CIRCLE_H_
+
+#include "common.h"
+#include "shape.h"
+
+struct _circle
+{
+    int invalid;
+
+    // super
+    struct _shape *shape;
+
+    // attribute
+    double radius;
+
+    // method
+    // void (*area)(void *self);
+    // void (*draw)(void *self);
+};
+
+struct _circle *circle_new(double radius);
+
+double circle_area(void *self, void *parent);
+void circle_draw(void *self, void *parent);
+
+#endif
diff --git a/library/common.h b/library/common.h
new file mode 100644
index 0000000..f64363a
--- /dev/null
+++ b/library/common.h
@@ -0,0 +1,11 @@
+
+#ifndef _COMMON_H_
+#define _COMMON_H_
+
+#include <stdint.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <assert.h>
+
+#endif
diff --git a/library/copper.c b/library/copper.c
new file mode 100644
index 0000000..0b1a3f8
--- /dev/null
+++ b/library/copper.c
@@ -0,0 +1,67 @@
+
+#include "copper.h"
+
+double copper_cash_area(struct _copper_cash *self, void *parent)
+{
+    // 如果用的继承，那么就不能直接调用父类的虚接口，实现自己。
+    // 因为父类虚接口，是自己实现的。这样相当于自己调用自己。导致卡死。
+
+    // 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 = 3.14 * self->circle->radius * self->circle->radius;
+    double rect_area = self->rect->width * self->rect->height;
+    double area = circle_area - rect_area;
+
+    printf("copper cash area = %0.2f\n", circle_area - rect_area);
+    return area;
+}
+
+void copper_cash_draw(struct _copper_cash *self, void *parent)
+{
+    printf("copper cash draw\n");
+}
+
+
+struct _copper_cash *copper_cash_new(double width, double height, double radius)
+{
+    // 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;
+    }
+    rect->shape = shape;
+
+    struct _circle *circle = circle_new(radius);
+    if (circle == NULL)
+    {
+        return NULL;
+    }
+    circle->shape = shape;
+
+    // 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;
+}
diff --git a/library/copper.h b/library/copper.h
new file mode 100644
index 0000000..4f5a20a
--- /dev/null
+++ b/library/copper.h
@@ -0,0 +1,24 @@
+
+#ifndef _COPPER_CASH_H_
+#define _COPPER_CASH_H_
+
+#include "common.h"
+#include "shape.h"
+#include "rect.h"
+#include "circle.h"
+
+struct _copper_cash
+{
+    struct _shape *shape;
+    struct _rect *rect;
+    struct _circle *circle;
+
+    double price;
+};
+
+struct _copper_cash *copper_cash_new(double width, double height, double radius);
+
+double copper_cash_area(struct _copper_cash *self, void *parent);
+void copper_cash_draw(struct _copper_cash *self, void *parent);
+
+#endif
diff --git a/library/list.c b/library/list.c
deleted file mode 100644
index ee6d6cc..0000000
--- a/library/list.c
+++ /dev/null
@@ -1,58 +0,0 @@
-
-#include "list.h"
-
-void list_init(struct list_t *list)
-{
-    list->data = 0;
-    list->next = NULL;
-}
-
-void list_add(struct list_t *list, uint8_t data)
-{
-    struct list_t *p = NULL;
-    p = list;
-    while (p->next != NULL)
-    {
-        p = p->next;
-        if (p->data == data)
-        {
-            return;
-        }
-    }
-    p->next = (struct list_t *)malloc(sizeof(struct list_t));
-    p->next->data = data;
-    p->next->next = NULL;
-    return;
-}
-
-void list_print(struct list_t *list)
-{
-    struct list_t *p = NULL;
-    p = list;
-    while (p->next != NULL)
-    {
-        printf("%02d ", p->data);
-        p = p->next;
-        if (p->next == NULL)
-        {
-            printf("%02d\n", p->data);
-            break;
-        }
-    }
-}
-
-void list_free(struct list_t *list)
-{
-    struct list_t *p = NULL;
-    p = list;
-    while (p->next != NULL)
-    {
-        p = p->next;
-        free(p->next);
-        p->next = NULL;
-        if (p->next == NULL)
-        {
-            break;
-        }
-    }
-}
diff --git a/library/list.h b/library/list.h
deleted file mode 100644
index 82f925c..0000000
--- a/library/list.h
+++ /dev/null
@@ -1,20 +0,0 @@
-
-#ifndef _LIST_H_
-#define _LIST_H_
-
-#include <stdint.h>
-#include <stdio.h>
-#include <stdlib.h>
-
-typedef struct list_t
-{
-    uint8_t  data;
-    struct list_t *next;
-} list_t;
-
-void list_init(struct list_t *list);
-void list_add(struct list_t *list, uint8_t data);
-void list_print(struct list_t *list);
-void list_free(struct list_t *list);
-
-#endif
diff --git a/library/rect.c b/library/rect.c
new file mode 100644
index 0000000..a70eebf
--- /dev/null
+++ b/library/rect.c
@@ -0,0 +1,59 @@
+
+#include "rect.h"
+
+double rect_area(void *self, void *parent)
+{
+    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)
+{
+    struct _rect *pthis = (struct _rect *)parent;
+    pthis->shape->vtb.draw(self, NULL);
+}
+
+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(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)
+    {
+        return NULL;
+    }
+    rect->width = width;
+    rect->height = height;
+    // set parent
+    rect->shape = shape;
+
+    return rect;
+}
diff --git a/library/rect.h b/library/rect.h
new file mode 100644
index 0000000..18c8bf9
--- /dev/null
+++ b/library/rect.h
@@ -0,0 +1,24 @@
+
+#ifndef _RECT_H_
+#define _RECT_H_
+
+#include "common.h"
+#include "shape.h"
+
+struct _rect
+{
+    int invalid;
+
+    // super
+    struct _shape *shape;
+
+    // attribute
+    double width, height;
+};
+
+struct _rect *rect_new(double width, double height);
+
+double rect_area(void *self, void *parent);
+void rect_draw(void *self, void *parent);
+
+#endif
diff --git a/library/shape.c b/library/shape.c
new file mode 100644
index 0000000..7d8037a
--- /dev/null
+++ b/library/shape.c
@@ -0,0 +1,75 @@
+
+#include "shape.h"
+
+double virtual_area(void *self, void *parent)
+{
+    ASSERT_CALL_VIRTUAL_METHOD();
+}
+
+void virtual_draw(void *self, void *parent)
+{
+    ASSERT_CALL_VIRTUAL_METHOD();
+}
+
+struct _virtual_table *virtual_new(void)
+{
+    struct _virtual_table *vtb = calloc(1, sizeof(struct _virtual_table));
+    if (vtb == NULL)
+    {
+        return NULL;
+    }
+    vtb->area = virtual_area;
+    vtb->draw = virtual_draw;
+    return vtb;
+}
+
+
+
+double shape_area(void *self, void *parent)
+{
+    double area = 0;
+    struct _shape *pthis = (struct _shape *)parent;
+    area = pthis->vtb.area(self, NULL);
+    return area;
+}
+
+void shape_draw(void *self, void *parent)
+{
+    struct _shape *pthis = (struct _shape *)parent;
+    pthis->vtb.draw(self, NULL);
+}
+
+PRIVATE double _shape_area(void *self, void *parent)
+{
+    ASSERT_CALL_VIRTUAL_METHOD();
+}
+
+PRIVATE void _shape_draw(void *self, void *parent)
+{
+    ASSERT_CALL_VIRTUAL_METHOD();
+}
+
+struct _shape *shape_new(void)
+{
+    struct _shape *shape = calloc(1, sizeof(struct _shape));
+    if(shape == NULL)
+    {
+        return NULL;
+    }
+    static struct _virtual_table vtb = {
+        .area = (double (*)(void *self, void *parent))_shape_area, 
+        .draw = (void (*)(void *self, void *parent))_shape_draw
+    };
+    shape->vtb = vtb;
+    return shape;
+}
+
+#if 0
+void shape_free(struct _shape * self)
+{
+    if (self != NULL)
+    {
+        free(self);
+    }
+}
+#endif
diff --git a/library/shape.h b/library/shape.h
new file mode 100644
index 0000000..aef632e
--- /dev/null
+++ b/library/shape.h
@@ -0,0 +1,30 @@
+
+#ifndef _SHAPE_H_
+#define _SHAPE_H_
+
+#include "common.h"
+
+#define VIRTUAL  
+#define PRIVATE static 
+
+#define ASSERT_CALL_VIRTUAL_METHOD() assert(!("can't call abstract method"))
+
+struct _virtual_table
+{
+    VIRTUAL double (*area)(void *self, void *parent);
+    VIRTUAL void (*draw)(void *self, void *parent);
+};
+
+struct _shape
+{
+    struct _virtual_table vtb;
+};
+
+
+struct _shape *shape_new(void);
+
+double shape_area(void *self, void *parent);
+void shape_draw(void *self, void *parent);
+
+#endif
+
diff --git a/src/main.c b/src/main.c
index 6e224e8..5970521 100644
--- a/src/main.c
+++ b/src/main.c
@@ -1,313 +1,8 @@
 
-#include <stdint.h>
-#include <stdio.h>
-#include <stdbool.h>
-#include <stdlib.h>
-#include <assert.h>
-
-#define VIRTUAL  
-#define PRIVATE static 
-
-#define ASSERT_CALL_VIRTUAL_METHOD() assert(!("can't call abstract method"))
-
-
-struct _virtual_table
-{
-    VIRTUAL double (*area)(void *self, void *parent);
-    VIRTUAL void (*draw)(void *self, void *parent);
-};
-
-double virtual_area(void *self, void *parent)
-{
-    ASSERT_CALL_VIRTUAL_METHOD();
-}
-
-void virtual_draw(void *self, void *parent)
-{
-    ASSERT_CALL_VIRTUAL_METHOD();
-}
-
-struct _virtual_table *virtual_new(void)
-{
-    struct _virtual_table *vtb = calloc(1, sizeof(struct _virtual_table));
-    if (vtb == NULL)
-    {
-        return NULL;
-    }
-    vtb->area = virtual_area;
-    vtb->draw = virtual_draw;
-    return vtb;
-}
-
-struct _shape
-{
-    struct _virtual_table vtb;
-};
-
-double shape_area(void *self, void *parent)
-{
-    double area = 0;
-    struct _shape *pthis = (struct _shape *)parent;
-    area = pthis->vtb.area(self, NULL);
-    return area;
-}
-
-void shape_draw(void *self, void *parent)
-{
-    struct _shape *pthis = (struct _shape *)parent;
-    pthis->vtb.draw(self, NULL);
-}
-
-PRIVATE double _shape_area(void *self, void *parent)
-{
-    ASSERT_CALL_VIRTUAL_METHOD();
-}
-
-PRIVATE void _shape_draw(void *self, void *parent)
-{
-    ASSERT_CALL_VIRTUAL_METHOD();
-}
-
-struct _shape *shape_new(void)
-{
-    struct _shape *shape = calloc(1, sizeof(struct _shape));
-    if(shape == NULL)
-    {
-        return NULL;
-    }
-    static struct _virtual_table vtb = {
-        .area = (double (*)(void *self, void *parent))_shape_area, 
-        .draw = (void (*)(void *self, void *parent))_shape_draw
-    };
-    shape->vtb = vtb;
-    return shape;
-}
-
-#if 0
-void shape_free(struct _shape * self)
-{
-    if (self != NULL)
-    {
-        free(self);
-    }
-}
-#endif
-
-struct _rect
-{
-    int invalid;
-
-    // super
-    struct _shape *shape;
-    // struct _shape;
-    // struct _virtual_table vtb;
-
-    // attribute
-    double width, height;
-
-    // method
-    // void (*area)(void *self);
-    // void (*draw)(void *self);
-};
-
-double rect_area(void *self, void *parent)
-{
-    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)
-{
-    struct _rect *pthis = (struct _rect *)parent;
-    pthis->shape->vtb.draw(self, NULL);
-}
-
-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(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)
-    {
-        return NULL;
-    }
-    rect->width = width;
-    rect->height = height;
-    // set parent
-    rect->shape = shape;
-
-    return rect;
-}
-
-struct _circle
-{
-    int invalid;
-
-    // super
-    struct _shape *shape;
-
-    // attribute
-    double radius;
-
-    // method
-    // void (*area)(void *self);
-    // void (*draw)(void *self);
-};
-
-double circle_area(void *self, void *parent)
-{
-    double area = 0;
-    struct _circle *pthis = (struct _circle *)parent;
-    area = pthis->shape->vtb.area(self, NULL);
-    return area;
-}
-void circle_draw(void *self, void *parent)
-{
-    struct _circle *pthis = (struct _circle *)parent;
-    pthis->shape->vtb.draw(self, NULL);
-}
-
-double _circle_area(void *self, void *parent)
-{
-    struct _circle *pthis = (struct _circle *)self;
-    double area = 3.14 * pthis->radius * pthis->radius;
-    printf("circle area = %0.2f\n", area);
-    return area;
-}
-void _circle_draw(void *self,  void *parent)
-{
-    printf("circle draw\n");
-}
-
-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;
-
-    return circle;
-}
-
-struct _copper_cash
-{
-    struct _shape *shape;
-    struct _rect *rect;
-    struct _circle *circle;
-
-    double price;
-};
-
-double copper_cash_area(struct _copper_cash *self, void *parent)
-{
-    // 如果用的继承，那么就不能直接调用父类的虚接口，实现自己。
-    // 因为父类虚接口，是自己实现的。这样相当于自己调用自己。导致卡死。
-
-    // 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 = 3.14 * self->circle->radius * self->circle->radius;
-    double rect_area = self->rect->width * self->rect->height;
-    double area = circle_area - rect_area;
-
-    printf("copper cash area = %0.2f\n", circle_area - rect_area);
-    return area;
-}
-
-void copper_cash_draw(struct _copper_cash *self, void *parent)
-{
-    printf("copper cash draw\n");
-}
-
-
-struct _copper_cash *copper_cash_new(double width, double height, double radius)
-{
-    // 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;
-    }
-    rect->shape = shape;
-
-    struct _circle *circle = circle_new(radius);
-    if (circle == NULL)
-    {
-        return NULL;
-    }
-    circle->shape = shape;
-
-    // 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;
-}
+#include "shape.h"
+#include "rect.h"
+#include "circle.h"
+#include "copper.h"
 
 int main(int argc, char *argv[])
 {