diff --git a/Day01-15/Day10/图形用户界面和游戏开发.md b/Day01-15/Day10/图形用户界面和游戏开发.md
index 9225cde..a92f535 100644
--- a/Day01-15/Day10/图形用户界面和游戏开发.md
+++ b/Day01-15/Day10/图形用户界面和游戏开发.md
@@ -264,7 +264,7 @@ class Ball(object):
             if distance < self.radius + other.radius \
                     and self.radius > other.radius:
                 other.alive = False
-               a self.radius = self.radius + int(other.radius * 0.146)
+                self.radius = self.radius + int(other.radius * 0.146)
 
     def draw(self, screen):
         """在窗口上绘制球"""