import java.applet.*;
import java.awt.*;
import java.awt.event.*;
import java.util.Random;

import javax.swing.Timer;

public class HeliEngine extends Applet implements ActionListener {

	Dimension dim;
	Random rg;
	Timer timer;
	int totalWallSegments, previousyLength = 50, x = 200;
	int[] xpos, yLength;
	Image image1, image2;

	public void init(){

		setSize(300,200);

		dim = getSize();
		rg = new Random();
		timer = new Timer(10,this);

		totalWallSegments = (dim.width/5);

		xpos = new int [totalWallSegments];
		yLength = new int [totalWallSegments];
		image1 = createBackground();

		// Populate xpos array
		for (int x = 0; x < xpos.length; x++)
		{
			xpos[x] = (x * 5);
		}

		setBackground (Color.BLACK);

		timer.start();

	}

	public void paint (Graphics g)
	{

		g.drawImage(image1,0-x,0,this);

		if (x % 300 == 0)
		{
			x = 0;
			image1 = image2;
			image2 = createBackground();

		}
		g.drawImage(image2,300-x,0,this);
	}

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

	public Image createBackground()
	{
		Image offscreen = createImage (dim.width, dim.height);

		Graphics imageg = offscreen.getGraphics();

		yLength = generateYLengths(previousyLength);

		imageg.setColor(Color.GREEN);
		for (int x = 0 ; x < totalWallSegments ; x++)
		{
			imageg.fillRect(xpos[x], 0, 5, yLength[x]);
			imageg.fillRect(xpos[x], (yLength[x]+(int)(dim.height/1.5)), 5, 1000);
		}

		return offscreen;

	}

	public int[] generateYLengths(int previousY)
	{
		int[] localyLength = new int[totalWallSegments];


		for (int x = 0; x < localyLength.length; x++)
		{
			int randomNumber = rg.nextInt(3)-1;

			if (randomNumber == -1 && previousY > 0)
			{
				localyLength[x] = previousY -= 5;
			}
			else if (randomNumber == 0)
			{
				localyLength[x] = previousY;
			}
			else if (randomNumber == 1 && (previousY+(dim.height/1.5)) < dim.height)
			{
				localyLength[x] = previousY += 5;
			}

			previousY = localyLength[x];
		}

		previousyLength = previousY;

		return localyLength;

	}

	public void actionPerformed(ActionEvent e)
	{
		x++;
		repaint();
	}





}