fixed issue where drawVerticle() was checking wrong boxes

src/main/java/dotsandboxes/DotsAndBoxesGrid.java

@@ -184,9 +184,9 @@ public class DotsAndBoxesGrid {
         }else{
             this.verticals[x][y] = true;
 
-            // Try to claim the north or south boxes
-            boolean claimN = claimBox(x, y-1, player);
-            boolean claimS = claimBox(x, y, player);
+            // Try to claim the left or right boxes
+            boolean claimN = claimBox(x, y, player);
+            boolean claimS = claimBox(x-1, y, player);
             if (claimN || claimS) {
                 notifyObservers();
                 return true;