From 822574361db03bc24bfddbf8d2ca98fcd4f823b6 Mon Sep 17 00:00:00 2001
From: dntzhang <dntzhang@qq.com>
Date: Mon, 19 Aug 2019 12:24:45 +0800
Subject: [PATCH] docs: update tutorial

---
 tutorial/kbone.md | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/tutorial/kbone.md b/tutorial/kbone.md
index 5f8713201..1830cb299 100644
--- a/tutorial/kbone.md
+++ b/tutorial/kbone.md
@@ -406,6 +406,8 @@ class Snake {
 }
 ```
 
+蛇的转向有个逻辑，就是不能反方向后退，比如正在向上移动，不能直接直接向下转向，所以在 `turnUp`,`turnRight`,`turnDown`,`turnLeft` 中都有对应的条件判断。
+
 ### 使用代码描述游戏实体
 
 ```js