diff --git a/playground/Demo/Demo28/Main.snow b/playground/Demo/Demo28/Main.snow
index d4b0fd4..1b709c3 100644
--- a/playground/Demo/Demo28/Main.snow
+++ b/playground/Demo/Demo28/Main.snow
@@ -6,6 +6,7 @@ module: Main
         fields:
             declare name: string
             declare age: int
+
         // 构造函数
         init:
             params:
@@ -17,11 +18,20 @@ module: Main
             end body
         end init
 
-        function: getAge
-            returns: int
+    function: getAge
+        returns: int
+        body:
+            // 获取字段 age
+            return this.age
+        end body
+    end function
+
+        function: setAge
+            params:
+                declare a: int
             body:
-                // 获取字段 age
-                return this.age
+                // 设置字段 age
+                this.age = a
             end body
         end function
     end struct
@@ -33,7 +43,12 @@ module: Main
             // 实例化一个叫A的Animal,并且调用构造函数
             declare a: Animal = new Animal("GenericAnimal", 1)
             // 直接调用已导入模块内的静态函数
-            os.print(a.getAge())
+            a.setAge(2)
+            os.println(a.getAge())
+            a.setAge(3)
+            os.println(a.getAge())
+
+
         end body
     end function
 end module
diff --git a/playground/Demo/Demo28/OS.snow b/playground/Demo/Demo28/OS.snow
index 5f9a738..7c6de6f 100644
--- a/playground/Demo/Demo28/OS.snow
+++ b/playground/Demo/Demo28/OS.snow
@@ -1,5 +1,4 @@
 module: os
-    // 模块级静态函数（被 import 后可直接调用）
     function: print
         params:
             declare i1: int
@@ -8,4 +7,12 @@ module: os
             syscall("PRINT", i1)
         end body
     end function
+        function: println
+            params:
+                declare i1: int
+            returns: void
+            body:
+                syscall("PRINTLN", i1)
+            end body
+        end function
 end module