public Main() {
        this.setSize(SIZE);

        JFrame frame = new JFrame(TITLE);

        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setLayout(new BorderLayout());
        frame.add(this, BorderLayout.CENTER);
        frame.pack();

        frame.setResizable(false);
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);

        instance = this;
    }