diff --git a/my_tree.py b/my_tree.py
index 823dbfc..d74a401 100644
--- a/my_tree.py
+++ b/my_tree.py
@@ -12,4 +12,17 @@ pen.up()
 pen.backward(150)    # 后退
 pen.down()
 
+def tree(n):
+    if n >= 50:
+        pen.forward(n)
+        pen.right(30)
+        tree(n-50)
+        pen.left(60)
+        tree(n-50)
+        pen.right(30)
+        pen.up()
+        pen.backward(n)
+        pen.down()
+
+tree(100)
 turtle.done()