Add main menu scene, setup framework for orientation switching

Assets/Scripts/UI/MainMenu.cs

@@ -0,0 +1,19 @@
+using UnityEngine;
+using UnityEngine.SceneManagement;
+
+public class MainMenu : MonoBehaviour
+{
+    public void StartGame()
+    {
+        // Replace with the actual scene name as set in Build Settings
+        SceneManager.LoadScene("AppleHillsOverworld");
+    }
+
+    public void QuitGame()
+    {
+        Application.Quit();
+#if UNITY_EDITOR
+        UnityEditor.EditorApplication.isPlaying = false;
+#endif
+    }
+}