@Override
 public void execute(IGameContext executionContext) {
   final EntityManager entityManager = executionContext.getContextFor(EntityManager.class);
   entityManager.clearAll();
   buildCreatures(entityManager);
   addFood(entityManager);
 }
 private void buildCreatures(EntityManager entityManager) {
   for (int i = 0; i < this.settings.getInitialCreatureCount(); i++) {
     final Vector2f position = randomPosition();
     final Vector2f velocity = randomVelocity();
     final ISiliconEntity newEntity = this.entityFactory.buildCritter(position, velocity);
     entityManager.addEntity(newEntity);
   }
 }