//Bouncing.java

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

public class Bouncing extends JApplet {

    int count, size, movesize, naptime;
	    
    public void init() {
	String input;
		
	input = JOptionPane.showInputDialog( "Enter number of loops" );
    	count = Integer.parseInt( input );

	input = JOptionPane.showInputDialog( "Enter size of circle" );
    	size = Integer.parseInt( input );

	input = JOptionPane.showInputDialog( "Enter distance of move" );
    	movesize = Integer.parseInt( input );

	input = JOptionPane.showInputDialog( "Enter sleep time in ms" );
    	naptime = Integer.parseInt( input );
    }
	
    public void paint (Graphics g) {
		
	int x=(int)(Math.random()*getWidth());  //random starting 
	int y=(int)(Math.random()*getHeight());
	int dir=(int)(Math.random()*4);   //random diagonal direction:
        	//0 is NE, 1 is SE, 2 is SW, 3 is NW

	for (int i=1; i<=count; i++) {
	    g.setColor( Color.WHITE );   
	    g.fillOval(x-size/2,y-size/2,size,size);  //erase current circle

	    if (dir == 0) {    //moving NE
		x = x + movesize;
		y = y - movesize;				
		if (y-size/2 <= 0)   //hit top,
		    dir = 1;  //change to SE.
		else if (x+size/2 >= getWidth())  //hit right,
		    dir = 3;               //change to NW
	    }
	    else if (dir == 1) {
		x = x + movesize;
		y = y + movesize;				
		if (x+size/2 >= getWidth())
		    dir = 2;
		else if (y+size/2 >= getHeight())
		    dir = 0;
	    }
	    else if (dir == 2) {
		x = x - movesize;
		y = y + movesize;				
		if (x-size/2 <= 0)
		    dir = 1;
		else if (y+size/2 >= getHeight())
		    dir = 3;
	    }
	    else if (dir == 3) {
		x = x - movesize;
		y = y - movesize;				
		if (y-size/2 <= 0)
		    dir = 2;
		else if (x-size/2 <= 0)
		    dir = 0;
	    }
	    
	    g.setColor( Color.RED );
	    g.fillOval(x-size/2,y-size/2,size,size);
	    
	    try {
		Thread.sleep(naptime);
	    }
	    catch (InterruptedException e) {
	    }
	}
    }
}