// NB: uses Java 1.1 event model...

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

public class bounce extends Applet 
	implements ActionListener, ItemListener, Runnable  {

	Vector	  colors = new Vector(0,13);
	Checkbox  gravity;
	Choice	  color;
	ball	  bouncer;

	public class ball extends Canvas {
		Rectangle position;
		Point	  speed;
		boolean	  xfast;

		private int abs(int x) {
			return (0>x)?-x:x;
		}

		private int sgn(int x) {
			return (0>x)?-1:(0<x)?1:0;
		}

		ball() {
			position = new Rectangle(30,20,12,12);
			speed = new Point(2,3);
			xfast = ( abs(speed.x) > abs(speed.y) );
		}

		private boolean canmove(Rectangle bounds, int dx, int dy) {
			Rectangle newrect = position.getBounds();
			newrect.translate(dx,dy);
			return( newrect.equals(newrect.intersection(bounds)) );
		}

		public int animate() {
			int dx;
			int dy;
			Dimension cd = getSize();
			Rectangle bounds =
				new Rectangle(0,0,cd.width,cd.height);
			if (xfast) {
				dx = sgn(speed.x);
				dy = 0;
			} else {
				dx = 0;
				dy = sgn(speed.y);
			}
			if ( !canmove(bounds,dx,dy) ) {
				if ( canmove(bounds,-dx,dy) ) {
					speed.x = -speed.x;
					dx = -dx;
				} else if ( canmove(bounds,dx,-dy) ) {
					speed.y = -speed.y;
					dy = -dy;
				} else {
					speed.x = -speed.x;
					dx = -dx;
					speed.y = -speed.y;
					dy = -dy;
				}
			}				
			position.translate(dx,dy);
			repaint();
			if (xfast) {
				if (0 != speed.x)
					return(100/abs(speed.x));
			} else {
				if (0 != speed.y)
					return(100/abs(speed.y));
			}
			return(1000);
		}

		public void gravitate() {
			speed.y += 1;
			xfast = ( abs(speed.x) > abs(speed.y) );
		}

		public void damp() {
			speed.x = 0;
			speed.y = 0;
		}

		public void kick() {
			int oldx = speed.x;
			int oldy = speed.y;
			do {
				speed.x = (int) ( 20.0 * (Math.random()-0.5) );
				speed.y = (int) ( 20.0 * (Math.random()-0.5) );
			} while ( (oldx==speed.x) && (oldy==speed.y) );
			xfast = ( abs(speed.x) > abs(speed.y) );			
		}

		public void paint(Graphics g) {
			g.fillOval(position.x,position.y,
				   position.width,position.height);
		}
	}

	public void run() {
		while (true) {
			int delay = bouncer.animate();
			try {
				Thread.sleep(delay);
			} catch (Exception e) {
				System.out.println("Who disturbs my sleep?");
			}
			if ( gravity.getState() )
				bouncer.gravitate();
		}
	}

// This method handles the buttons.

	public void actionPerformed(ActionEvent e) {
		switch(e.getActionCommand().charAt(0)) {
		case 'd':
			bouncer.damp();
			break;
		case 'k':
			bouncer.kick();
			break;
		}			
	}

// Color choice
// Took out repaint because it's going to get done soon anyway...

	public void itemStateChanged(ItemEvent e) {
		bouncer.setForeground(
		    (Color) colors.elementAt(color.getSelectedIndex()));
	}

// Add color choice to menu

	private void acc(String name, Color tint) {
		color.add(name);
		colors.addElement(tint);
	}

// Startup the applet

	public void init() {
		setLayout( new BorderLayout() );
		Panel panel = new Panel();
		panel.setLayout( new GridLayout(4,1) );

		color = new Choice();
		acc("black",    Color.black);
		acc("blue",     Color.blue);
		acc("cyan",     Color.cyan);
		acc("darkGrey", Color.darkGray);
		acc("grey",     Color.gray);
		acc("green",    Color.green);
		acc("lightGrey",Color.lightGray);
		acc("magenta",  Color.magenta);
		acc("orange",   Color.orange);
		acc("pink",     Color.pink);
		acc("red",      Color.red);
		acc("yellow",   Color.yellow);
		color.addItemListener(this);
		panel.add(color);

		gravity = new Checkbox("Gravity");
		panel.add(gravity);

		Button damp = new Button("arrete");
		damp.addActionListener(this);
		damp.setActionCommand("d");
		panel.add(damp);

		Button kick = new Button("coup");
		kick.addActionListener(this);
		kick.setActionCommand("k");
		panel.add(kick);

		bouncer = new ball();
		bouncer.setBackground(Color.white);
		bouncer.setForeground(Color.black);

		add(bouncer,"Center");
		add(panel,"East");

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