import java.applet.Applet;
import java.applet.*;
import java.awt.*;

public class manyball extends Applet implements Runnable {
    private Color background;
    private Color foreground;
    private boolean running;
    public Image image;
    public Graphics offscreen;
    public Thread runner;
    private boolean bump;
    //border sizes
    static final int startX=10;
    static final int startY=10;
    private int maxX;
    private int maxY;
    //sounds
    AudioClip beep;
    AudioClip hurt;
    AudioClip gong;
    static final int maxBalls=4;
    ball b[];
    
	public void init() {
		//allocate balls 
    		b = new ball[maxBalls];
    		b[0] = new ball(20,150,Color.red,20,2,2);
    		b[1] = new ball(32,78,Color.blue,35,1,-3);
    		b[2] = new ball(223,218,Color.green,40,-3,-2);
    		b[3] = new ball(10,15,Color.gray,25,-3,-1);
    
        	background = Color.black;
        	foreground = Color.black;
        	//find screen size
        	maxX=size().width;
        	maxY=size().height;
        	//create offscreen image
        	image=createImage(maxX,maxY);
        	offscreen=image.getGraphics();
        	Font f=new Font("Dialog",Font.BOLD,10);
        	offscreen.setFont(f);
        	offscreen.drawString("Bouncing Balls 3.0",9,10);
        	//sounds
        	beep=getAudioClip(getDocumentBase(),"beep.au");
        	hurt=getAudioClip(getDocumentBase(),"hurts.au");
        	gong=getAudioClip(getDocumentBase(),"chirp1.au");
    	}
  
        public void update(Graphics g) {
    		paint(g);
   	}
  
   	public void paint(Graphics g) {
   		offscreen.setColor(background);
     		offscreen.fillRect(startX,startY,maxX-startX,maxY-startY);
    		bump=false;
    		for (int i=0; i<maxBalls; i++) {
    			b[i].drawBall();
    			for (int j=0; j<maxBalls; j++) {
    				if (j!=i) {
    					hit (b[i].xPos+2,b[i].yPos+2,(b[i].diameter+b[i].xPos-2),(b[i].diameter+b[i].yPos-2),b[j].xPos+2,b[j].yPos+2,(b[j].diameter+b[j].xPos-2),(b[j].diameter+b[j].yPos-2));
    				}
    				if (bump) {
    					newPath(i,j);    					
    				}
    			}
     		}
     		g.drawImage(image,0,0,this);
      	}
    
    	public void destroy() {
    		offscreen.dispose();
        }
        
        public void start() {
        	if (runner==null) {
        		runner=new Thread(this);
        		runner.start();
        		running=true;
        	}
        }
        
        public void stop() {
        	running=false;
        }
        
        public void run() {
        	try {
            		while (running) {
            			runner.sleep(40);
            			repaint();
            		}
        	} 
        	catch(InterruptedException e) {
            	running = false;
            	}
        }
        
        public void hit (int x1, int y1, int x2, int y2, int x3, int y3, int x4, int y4) {
        	if ((x1>=x3) && (x4>=x1) && (y2>=y3) && (y4>=y1)) {
        		bump=true;
        	}
        }
        
        public void newPath (int i, int j) {
        	int temp;
        	b[i].moveX*=-1;
    		b[i].xPos+=b[i].moveX;
    		temp=b[i].moveX;
    		b[i].moveX=b[i].moveY;
    		b[i].moveY=temp;
    		b[i].yPos+=b[i].moveY;
    		b[i].drawBall();
    		b[j].moveX*=-1;
    		b[j].xPos+=b[j].moveX;
    		temp=b[j].moveX;
    		b[j].moveX=b[j].moveY;
    		b[j].moveY=temp;
    		b[j].yPos+=b[j].moveY;
    		b[j].drawBall();
    		if (gong!=null) {
    			gong.play();
    		}
    		bump=false;
    	}
    	
        class ball {
        	//instance variables
        	int xPos;
        	int yPos;
        	Color ballColor;
        	int moveX;
        	int moveY;
        	int diameter;
    
        	//constructor
        	public ball (int xPos, int yPos, Color ballColor,int diameter, int moveX, int moveY) {
        		this.xPos=xPos;
        		this.yPos=yPos;
        		this.ballColor=ballColor;
        		this.diameter=diameter;
        		this.moveX=moveX;
        		this.moveY=moveY;
        	}
        	
        	//calculate positions and draw ball to offscreen image
        	public void drawBall() {
        		if (xPos+moveX<startX || xPos+diameter>maxX) {
        			moveX*=-1;
        			if (beep!=null) {
        				beep.play();
        			}
        			if (xPos+moveX<startX) xPos=startX;
        			if (xPos+diameter>maxX) xPos=maxX-diameter;
        		}
        		else if (yPos+moveY<startY || yPos+diameter>maxY) {
        			moveY*=-1;
        			if (hurt!=null) {
        				hurt.play();
        			}
        			if (yPos+moveY<startY) yPos=startY;
        			if (yPos+diameter>maxY) yPos=maxY-diameter;
        			
        		}
        		xPos+=moveX;
        		yPos+=moveY;
        		offscreen.setColor(ballColor);
	        	offscreen.fillOval(xPos,yPos,diameter,diameter);
	       	}
	}
}