Update bug list

README.md

@@ -133,3 +133,10 @@ The signs used in the level will become the sign used in the game, so try to put
 13.<img src = "README_IMAGE/13.PNG" width = "30">
 14.<img src = "README_IMAGE/14.PNG" width = "30">
 15.<img src = "README_IMAGE/15.PNG" width = "30">
+
+## Exisiting Bug
+
+1. A lag happened when frequently clicked the **restart button** and **start button**.
+2. When the game runs for a long time, it may causes **memory leak**
+
+Fortunately, bugs on the above are located.
\ No newline at end of file