Time for action – changing the grid with GridController

The GridController object initiates all grid changes since it's where we handle touches. In the game, the user can drag a gem to swap places with another, or first select the gem they want to move and then select the gem they want to swap places with in a two-touch process. Let's add the touch handling for that:

1. In GridController, let's add the logic to onTouchDown:

   function GridController:onTouchDown (touch)
       if (self.gameLayer.running == false) then
           local scene = require("GameScene")
           local gameScene = scene.create()
           cc.Director:getInstance():replaceScene(gameScene)
           local bgMusicPath =  cc.FileUtils:getInstance():fullPathForFilename("background.mp3") 
           cc.SimpleAudioEngine:getInstance():playMusic(bgMusicPath, true)
           return 
       end

   If we are displaying the game over screen, restart the scene.

2. Next, we find the gem the user is trying to select:

    ...