Add new field to controller.

src/Controller.java

+import java.awt.*;
+import java.awt.image.BufferedImage;
+import java.util.ArrayList;
+
 public class Controller {
     public static String userName;
+    public static ArrayList<Wall> walls;
+    public static Graphics2D g2d;
+    public static BufferedImage taken;
+    public static int row;
+    public static int col;
 }