gamepanel

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

public class GamePanel extends JPanel implements ActionListener {

    static final int SCREEN_WIDTH = 1300;
    static final int SCREEN_HEIGHT = 750;
    static final int UNIT_SIZE = 40;
    static final int GAME_UNITS = (SCREEN_WIDTH * SCREEN_HEIGHT) / UNIT_SIZE;
    static final int DELAY = 150;
    int x[] = new int[GAME_UNITS];
    int y[] = new int[GAME_UNITS];
    int bodyParts = 4;
    int appleEaten;
    int appleX;
    int appleY;
    char direction = 'R';
    boolean running = false;
    Timer timer;
    Random random;

    GamePanel(){
        random = new Random();
        this.setPreferredSize(new Dimension(SCREEN_WIDTH,SCREEN_HEIGHT));
        this.setBackground(new Color(26,27,37));
        this.setFocusable(true);
        this.addKeyListener(new MyKeyAdapter());
        startGame();
    }
    public void startGame(){
        newApple();
        running = true;
        timer = new Timer(DELAY,this);
        timer.start();
    }
    public void paintComponent(Graphics g){
        super.paintComponent(g);
        draw(g);
    }
    public void draw(Graphics g) {
        if (running) {
            g.setColor(Color.red);
            g.fillOval(appleX, appleY, UNIT_SIZE-8, UNIT_SIZE-8);
            int intensity=255;
            for (int i = 0; i < bodyParts; i++) {
                if (i == 0) {
                    g.setColor(new Color(27,200,139,255));
                    g.fillRect(x[i], y[i], UNIT_SIZE-1, UNIT_SIZE-1);
                } else {
                    g.setColor(new Color(27, 153, 139,intensity));
                    intensity -= 2;
                    g.fillRect(x[i], y[i], UNIT_SIZE-1, UNIT_SIZE-1);
                }
            }
            g.setColor(new Color(120,153,212));
            g.setFont(new Font("Fira Sans Regular",Font.PLAIN,35));
            FontMetrics metrics = getFontMetrics(g.getFont());
            g.drawString("Score: "+appleEaten,(SCREEN_WIDTH-metrics.stringWidth("Score: "+appleEaten))/2,g.getFont().getSize());
        }
        else{
            gameOver(g);
        }
    }
    public void newApple(){
        appleX = random.nextInt((int)(SCREEN_WIDTH/UNIT_SIZE))*UNIT_SIZE;
        appleY = random.nextInt((int)(SCREEN_HEIGHT/UNIT_SIZE))*UNIT_SIZE;
    }
    public void move(){
        for(int i=bodyParts;i>0;i--){
            x[i] = x[i-1];
            y[i] = y[i-1];
        }
        switch (direction){
            case 'U':
                y[0] = y[0]-UNIT_SIZE;
                break;
            case 'D':
                y[0] = y[0]+UNIT_SIZE;
                break;
            case 'L':
                x[0] = x[0]-UNIT_SIZE;
                break;
            case 'R':
                x[0] = x[0]+UNIT_SIZE;
                break;
        }
    }
    public void checkApple(){
        if((x[0]==appleX)&&(y[0]==appleY)){
            bodyParts++;
            appleEaten++;
            newApple();
        }
    }
    public void checkCollisions(){
        //check if head collides with the body
        for(int i=bodyParts;i>0;i--)
            if ((x[0] == x[i]) && (y[0] == y[i]))
                running = false;

        //check if head touches left borders
        if(x[0]<0)
            running = false;
        //if head touches right border
        if(x[0]>SCREEN_WIDTH)
            running = false;
        //if head touches top border
        if(y[0]<0)
            running = false;
        //if head touches bottom border;
        if(y[0]>SCREEN_HEIGHT)
            running = false;
        if(!running)
            timer.stop();
    }
    public void gameOver(Graphics g){
        //score
        g.setColor(new Color(120,153,212));
        g.setFont(new Font("Fira Sans Regular",Font.PLAIN,35));
        FontMetrics metrics1 = getFontMetrics(g.getFont());
        g.drawString("Score: "+appleEaten,(SCREEN_WIDTH-metrics1.stringWidth("Score: "+appleEaten))/2,g.getFont().getSize());
        //game over text
        g.setColor(new Color(255,0,0,200));
        g.setFont(new Font("Monospace Regular",Font.PLAIN,60));
        FontMetrics metrics = getFontMetrics(g.getFont());
        g.drawString("Game Over",(SCREEN_WIDTH-metrics.stringWidth("Game Over"))/2,(int)((double)SCREEN_HEIGHT/2.5));
        //restart button
        g.setColor(new Color(248,241,255));
        g.setFont(new Font("Monospace Regular",Font.ITALIC,50));
        FontMetrics metrics2 = getFontMetrics(g.getFont());
        g.drawString("Press SPACE to play again",(SCREEN_WIDTH-metrics2.stringWidth("Press SPACE to play again"))/2,(int) ((double)SCREEN_HEIGHT/1.8));
    }
    public void restart(){
        startGame();
        repaint();
        bodyParts = 4;
        direction = 'R';
        appleEaten = 0;
        for(int i=0;i<4;i++){
            x[i]=0;
            y[i]=0;
        }
    }
    @Override
    public void actionPerformed(ActionEvent e) {
        if(running){
            move();
            checkApple();
            checkCollisions();
        }
        repaint();
    }
    public class MyKeyAdapter extends KeyAdapter{
        @Override
        public void keyPressed(KeyEvent e){
            switch (e.getKeyCode()){
                case KeyEvent.VK_LEFT:
                    if(direction != 'R')
                        direction = 'L';
                    break;
                case KeyEvent.VK_RIGHT:
                    if(direction != 'L')
                        direction = 'R';
                    break;
                case KeyEvent.VK_UP:
                    if(direction != 'D')
                        direction = 'U';
                    break;
                case KeyEvent.VK_DOWN:
                    if(direction != 'U')
                        direction = 'D';
                    break;
                case KeyEvent.VK_SPACE:
                    if(running == false)
                        restart();
                    break;
            }
        }
    }
}