import javax.swing.*;
import java.awt.*;
import java.awt.event.*;

class WindowPanel extends JPanel implements ActionListener, KeyListener
{
    public static final int M_TILE   = 25;
    public static final int M_WIDTH  = M_TILE * 25;
    public static final int M_HEIGHT = M_TILE * 25;
    public static final int M_FPS    = 15;
    public static final int M_DELAY  = 1000 / M_FPS;

    private Timer m_timer = new Timer( M_DELAY, this );
    private Font  m_font  = new Font( "MS Gothic", Font.PLAIN, 100 );
    
    private int m_iFruitX, m_iFruitY;
    private int m_iSnakeLength = 4;
    private char m_cDir = 'r';		// r, l, u, d
    private boolean m_bGameOver = false;
    private int[] m_iSnakeX, m_iSnakeY;
    
    @Override public void paintComponent( Graphics g )
    {
        super.paintComponent( g );
        // Snake        
        g.setColor( Color.GREEN );
        for ( int i = 0; i < m_iSnakeLength; i++ )
            g.fillRect( m_iSnakeX[ i ], m_iSnakeY[ i ], M_TILE, M_TILE );
        // Fruit
        g.setColor( Color.RED );
        g.fillRect( m_iFruitX, m_iFruitY, M_TILE, M_TILE );
        // Grid
        g.setColor( Color.WHITE );
        for ( int i = 0; i < M_WIDTH; i += M_TILE )
            for ( int j = 0; j < M_HEIGHT; j += M_TILE )
                g.drawRect( i, j, M_TILE, M_TILE );
        // Game Over
        if ( m_bGameOver ) {
            g.setColor( Color.YELLOW );
            g.setFont( m_font );
            g.drawString( "GAME OVER", M_WIDTH / 2 - 233, M_HEIGHT / 2 );
        }
        g.dispose();
    }

    @Override public void actionPerformed( ActionEvent e )
    {
        if ( !m_bGameOver ) {
            for ( int i = m_iSnakeLength; i > 0; i-- ) {
                m_iSnakeX[ i ] = m_iSnakeX[ i - 1 ];
                m_iSnakeY[ i ] = m_iSnakeY[ i - 1 ];
            }
            if ( m_cDir == 'r' ) m_iSnakeX[ 0 ] += M_TILE;
            if ( m_cDir == 'l' ) m_iSnakeX[ 0 ] -= M_TILE;
            if ( m_cDir == 'u' ) m_iSnakeY[ 0 ] -= M_TILE;
            if ( m_cDir == 'd' ) m_iSnakeY[ 0 ] += M_TILE;
            if ( m_iSnakeX[ 0 ] < 0 )
                m_iSnakeX[ 0 ] = M_WIDTH;
            if ( m_iSnakeY[ 0 ] < 0 )
                m_iSnakeY[ 0 ] = M_HEIGHT;
            if ( m_iSnakeX[ 0 ] > M_WIDTH )
                m_iSnakeX[ 0 ] = 0;
            if ( m_iSnakeY[ 0 ] > M_HEIGHT )
                m_iSnakeY[ 0 ] = 0;
            if ( m_iSnakeX[ 0 ] == m_iFruitX &&
                 m_iSnakeY[ 0 ] == m_iFruitY ) {
                m_iSnakeLength++;
                m_iFruitX = new java.util.Random().nextInt( M_WIDTH  / M_TILE );
                m_iFruitY = new java.util.Random().nextInt( M_HEIGHT / M_TILE );
                m_iFruitX *= M_TILE;
                m_iFruitY *= M_TILE;
            }
            for ( int i = m_iSnakeLength; i > 0; i-- ) {
                if ( m_iSnakeX[ 0 ] == m_iSnakeX[ i ] &&
                     m_iSnakeY[ 0 ] == m_iSnakeY[ i ] )
                    m_bGameOver = true;
            }
        }
        repaint();
    }

    @Override public void keyPressed( KeyEvent e )
    {
        if ( e.getKeyCode() == KeyEvent.VK_RIGHT )
            if ( m_cDir != 'l' )
                m_cDir = 'r';
        if ( e.getKeyCode() == KeyEvent.VK_LEFT )
            if ( m_cDir != 'r' )
                m_cDir = 'l';
        if ( e.getKeyCode() == KeyEvent.VK_UP )
            if ( m_cDir != 'd' )
                m_cDir = 'u';
        if ( e.getKeyCode() == KeyEvent.VK_DOWN )
            if ( m_cDir != 'u' )
                m_cDir = 'd';
    }

    @Override public void keyTyped( KeyEvent e ) {}
    @Override public void keyReleased( KeyEvent e ) {}
    
    public WindowPanel()
    {
        this.setFocusable( true );
        this.setDoubleBuffered( true );
        this.setPreferredSize( new Dimension( M_WIDTH, M_HEIGHT ) );
        this.setBackground( Color.BLACK );
        this.addKeyListener( this );
        m_iFruitX = new java.util.Random().nextInt( M_WIDTH  / M_TILE );
        m_iFruitY = new java.util.Random().nextInt( M_HEIGHT / M_TILE );
        m_iFruitX *= M_TILE;
        m_iFruitY *= M_TILE;
        m_iSnakeX = new int[ 200 ];
        m_iSnakeY = new int[ 200 ];
        m_timer.start();
    }
}

public class Main extends JFrame
{
    public Main()
    {
        this.add( new WindowPanel() );
        this.pack();
        this.setTitle( "Snake" );
        this.setResizable( false );
        this.setLocationRelativeTo( null );
        this.setVisible( true );
        this.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
    }

    public static void main( String[] args )
    {
        new Main();
    }
}