feat: control game volumn

assets/scripts/Game.js

@@ -318,6 +318,7 @@ cc.Class({
         this.board.active = false
         this.teacher.active = false
         this.gameState = 'waiting'
+        this.bgMusic.volume = 1
 
         var remoteDomain = 'https://nzr2ybsda.qnssl.com/images/153823/'
         var pictures = [

assets/scripts/Start.js

@@ -17,6 +17,7 @@ cc.Class({
             self.game.level.progress = 1
             self.game.gameState = 'action'
             self.game.teacher.getComponent("Teacher").startSwivel()
+            self.game.bgMusic.volume = 0.5
         })
     },