難易度に異次元追加, 背景追加

popcorn/Assets/MyGame/Scenes/MiniGame/Scripts/BackGround.cs

@@ -26,6 +26,9 @@ namespace MyGame.Scenes.MiniGame.Scripts
                 case ScrollGameDifficulty.Hard:
                     animator.Play("sky_switching_b_c", 0, 0f);
                     break;
+                case ScrollGameDifficulty.Extra:
+                    animator.Play("sky_switching_c_d", 0, 0f);
+                    break;
                 default:
                     throw new ArgumentOutOfRangeException(nameof(difficulty), difficulty, null);
             }

popcorn/Assets/MyGame/Scripts/SpreadsheetData.cs

@@ -172,6 +172,7 @@ public enum ScrollGameDifficulty
     Easy = 1,
     Normal = 2,
     Hard = 3,
+    Extra = 4
 }
 
 [Serializable]