Add 2 and 4

src/main/java/controller/MainWindowController.java

@@ -112,7 +112,7 @@ public class MainWindowController implements IObserver {
                 }
 
                 gc.fillText("" + value, x + (this.squareSize / 2), y + (this.squareSize / 2));
-                
+
             }
         }
     }

src/main/java/model/Board.java

@@ -88,10 +88,17 @@ public class Board implements IModel{
         if(choices.size()>0){
             int index=0;
             if(choices.size()>1){
-                index=rand.nextInt(choices.size()-1) + 0;
+                index=rand.nextInt(choices.size()-1 +1) + 0;
             }
             Integer[] xy=(Integer[])choices.toArray()[index];
-            this.board[xy[0]][xy[1]]=2;
+            int twoOrFour=rand.nextInt(3-0 +1) + 0;
+            switch (twoOrFour){
+                case 0:
+                    this.board[xy[0]][xy[1]]=4;
+                    break;
+                default:
+                    this.board[xy[0]][xy[1]]=2;
+            }
         }
     }