import java.applet.Applet;
import java.awt.Graphics;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Image;

public class Sample4 extends Applet implements Runnable{

    Thread thread = null;
    Dimension size;
    Image back;
    Graphics buffer;

    int block[][];
    int dx[] = {0, 1, 0, -1};
    int dy[] = {1, 0, -1, 0};

    public void init(){
        size = getSize();
        back = createImage(size.width, size.height);
        buffer = back.getGraphics();

        block = new int[21][21];
        makeMaze();

        thread = new Thread(this);
        thread.start();
    }

    private void makeMaze(){
        /* 全体をクリア */
        for (int i = 0 ; i < 21 ; i++){
            for (int j = 0 ; j < 21 ; j++){
                block[i][j] = 0;
            }
        }

        /* 外枠をセット */
        for (int i = 0 ; i < 21 ; i++){
            block[0][i] = 1;
            block[20][i] = 1;
            block[i][0] = 1;
            block[i][20] = 1;
        }

        /* 基準点をセット */
        for (int i = 1 ; i <= 9 ; i++){
            for (int j = 1 ; j <= 9 ; j++){
                block[i * 2][j * 2] = 1;
            }
        }

        /* 迷路作成 */
        for (int i = 1 ; i <= 9 ; i++){
            for (int j = 1 ; j <= 9 ; j++){
                if (i == 1){
                    int d = (int)(Math.random() * 4);
                    block[i * 2 + dx[d]][j * 2 + dy[d]] = 1;
                }else{
                    boolean flag = true;
                    while(flag){
                        int d = (int)(Math.random() * 3);
                        if (block[i * 2 + dx[d]][j * 2 + dy[d]] == 0){
                            block[i * 2 + dx[d]][j * 2 + dy[d]] = 1;
                            flag = false;
                        }
                    }
                }
            }
        }
    }

    public void update(Graphics g){
        paint(g);
    }

    public void paint(Graphics g){
        buffer.setColor(Color.black);
        buffer.fillRect(0, 0, size.width, size.height);

        for (int i = 0 ; i < 21 ; i++){
            for (int j = 0 ; j < 21 ; j++){
                if (block[i][j] == 1){
                    buffer.setColor(Color.white);
                    buffer.fillRect(j * 15, i * 15, 15, 15);

                    buffer.setColor(Color.blue);
                    buffer.drawRect(j * 15 + 1, i * 15 + 1, 13, 13);
                }
            }
        }

        buffer.setColor(Color.red);
        buffer.fillRect(15 + 1, 15 + 1, 13, 13);

        buffer.setColor(Color.blue);
        buffer.fillRect(15 * 19 + 1, 15 * 19 + 1, 13, 13);

        g.drawImage(back, 0, 0, this);
    }

    public void run(){
        while(true){
            repaint();

            makeMaze();

            /* 5000ミリ秒待機する */
            try{
                Thread.sleep(5000);
            }catch (InterruptedException e){
            }

        }
    }

}