World(int level) {
        walls = new ArrayList<Wall>();
        walls.add(new Wall(0, 0, 600, 20));
        walls.add(new Wall(0, 0, 20, 600));
        walls.add(new Wall(0, 571, 600, 600));
        walls.add(new Wall(571, 0, 600, 600));
        switch(level) {
            case 1: initWorldLevelOne(); break;
            case 2: initWorldLevelTwo(); break;
            case 3: initWorldLevelThree(); break;
        }
    }