Ich habe einen Score Actor hinzugefügt, welcher den Score oben im Bildschirm anzeigt und jede Sekunde um eins erhöht.

SMIMS-Game/Score.java

@@ -0,0 +1,29 @@
+import greenfoot.*;  // (World, Actor, GreenfootImage, Greenfoot and MouseInfo)
+
+/**
+ * Write a description of class UI here.
+ * 
+ * @author (your name) 
+ * @version (a version number or a date)
+ */
+public class Score extends Actor
+{
+    int timer;
+    /**
+     * Act - do whatever the UI wants to do. This method is called whenever
+     * the 'Act' or 'Run' button gets pressed in the environment.
+     */
+    public void act()
+    {
+        timer++;
+        draw_score();
+    }
+    
+    public void draw_score(){
+        setImage(new GreenfootImage("Score:" + calculate_score(), 24, Color.WHITE, Color.BLACK));
+    }
+    
+    public int calculate_score(){
+        return timer/60;
+    }
+}