蛇体看起来像一条直线

Question

我正在制作蛇游戏;蛇在光标后面移动。蛇的运动很完美，但它的身体看起来像一条圆圈。

哪里的圈子应该出现在自己的盒子里。我调试了程序并试图弄清楚问题，但是在得到每个圈子的x位置和y位置的值后我感到困惑，因为它显示了一个差距btw每个圆圈有20个像素（圆圈大小），因此它应该在自己的方框中显示它们但不是。我无法弄清问题在哪里，这是我的类代码，它吸引蛇并移动它：

`import java.awt.Color;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.MouseEvent;
import java.awt.event.MouseMotionListener;
import javax.swing.JFrame;
import javax.swing.JPanel;

public class Game extends JPanel implements MouseMotionListener {
    int x_Cur;
    int y_Cur;
    int dots;
    int delta_x, delta_y;
    double angle;
    double x_inc, y_inc;
    double speed = 5.0;
    int max_points = (600 * 600);
    final int x_positions[] = new int[max_points];
    final int y_positions[] = new int[max_points];

    public Game() {
        addMouseMotionListener(this);
        setFocusable(true);
        setPreferredSize(new Dimension(600, 600));
        setVisible(true);
        first_Snake();
    }

    @Override
    protected void paintComponent(Graphics g) {

        super.paintComponent(g);
        Graphics2D g2d = (Graphics2D) g;
        g2d.setColor(Color.green);
        for (int z = 0; z < dots; z++) {
            if (z == 0) {
                g.setColor(Color.yellow);
                g.fillOval(x_positions[z], y_positions[z], 20, 20);
            } else {
                g.setColor(Color.green);
                g.fillOval(x_positions[z], y_positions[z], 20, 20);
            }
            System.out.println("xs"+z+"="+x_positions[z]+"\n"+"ys"+z+"="+y_positions[z]);
        }

        try {
            Thread.sleep(10);
        } catch (Exception e) {
        }
        delta_x = x_Cur - x_positions[0];
        delta_y = y_Cur - y_positions[0];
        angle = Math.atan2(delta_y, delta_x);
        double speed = Math.sqrt(delta_x * delta_x + delta_y * delta_y);
        speed = Math.min(speed, 2.5);
        x_inc = (speed * Math.cos(angle));
        y_inc = (speed * Math.sin(angle));
        move();
    }
    public void move(){
        if(!(delta_x==0&&delta_y==0)){
            for (int z = dots; z > 0; z--) {
                x_positions[z] = x_positions[z-1];
                y_positions[z] = y_positions[z-1];  
            } 
    }
        x_positions[0]+= x_inc;
        y_positions[0]+= y_inc;
            action();

    }
    public void action(){
        repaint();
    }

    public void first_Snake() {

        dots = 20;
        for (int z = 0; z < dots; z++) {
            x_positions[z] = 50 - z * 20;
            y_positions[z] = 50;
        }

    }

    @Override
    public void mouseDragged(MouseEvent me) {

    }

    @Override
    public void mouseMoved(MouseEvent me) {

        x_Cur = me.getX() - 20;
        y_Cur = me.getY() - 20;

    }
}`

这是包含主要方法的类：

    import java.awt.EventQueue;
import javax.swing.JFrame;

public class Snake extends JFrame {

    public Snake() {
        add(new Game());
         setTitle("Snake");
            pack();
            setResizable(false);
            setLocationRelativeTo(null);
            setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        }
     public static void main(String[] args) {
            EventQueue.invokeLater(new Runnable() {

                @Override
                public void run() {                
                    JFrame ex = new Snake();

                    ex.setVisible(true);                
                }
            });
        }
}

请帮忙。