@Transient
  public Level getPreviousLevel() {
    int currentLevelNr = state.getCurrentLevelNr();

    if (currentLevelNr == 0) {
      return null;
    }

    return levelMap.get(state.getCurrentLevelNr() - 1);
  }
  @Transient
  public Level getNextLevel() {
    int currentLevelNr = state.getCurrentLevelNr();

    if (currentLevelNr == levelMap.size()) {
      return null;
    }

    return levelMap.get(state.getCurrentLevelNr() + 1);
  }
 @Transient
 public Level getCurrentLevel() {
   return levelMap.get(state.getCurrentLevelNr());
 }