import java.awt.*;import java.applet.Applet;class Piece extends Object {	int		x, y, width, height, unit;	int		xloc, yloc;		public Piece (int xloc, int yloc, int x, int y, int width, int height, int unit) {		this.xloc = xloc;		this.yloc = yloc;		this.x = x;		this.y = y;		this.width = width;		this.height = height;		this.unit = unit;	}		public void drawPiece (Graphics g, Image pieceImage) {		int x = (xloc * unit) + (unit >> 1);		int y = (yloc * unit) + (unit >> 1);		Graphics gcopy = g.create();		gcopy.clipRect(x, y, width * unit, height * unit);		gcopy.drawImage(pieceImage, x - (this.x * unit), y - (this.y * unit), null);		gcopy.dispose();	}		public boolean intersects (Piece piece, int x, int y) {		if (((x + piece.width - 1) < xloc)  ||  (x > (xloc + width - 1)))			return false;		if (((y + piece.height - 1) < yloc)  ||  (y > (yloc + height - 1)))			return false;		return true;	}		public boolean picks (int x, int y) {		if (x < xloc  ||  x > (xloc + width - 1)  ||  y < yloc ||  y > (yloc + height - 1))			return false;		return true;	}		public boolean onBoard (int x, int y) {		if (x < 0  ||  y < 0  ||  (x + width) > 4  ||  (y + height) > 5)			return false;		return true;	}	public void moveTo (int x, int y) {		this.xloc = x;		this.yloc = y;	}}class PuzzleBoard extends Canvas {	private Image			offscreenImage, boardImg, piecesImg;	private int			width, height, unit, pickedX, pickedY, pickedXoff, pickedYoff, lastX, lastY;	private int			widthBoard, heightBoard, widthPieces, heightPieces;	private Graphics		offscr;	private Piece[]		pieces = new Piece[10];	private Piece			pickedPiece = null;	public PuzzleBoard (int x, int y, int width, int height, Applet a) {		super();		this.width = width;		this.height = height;	 	MediaTracker tracker = new MediaTracker(this);		tracker.addImage(boardImg = a.getImage(a.getCodeBase(), "board.gif"), 0);		tracker.addImage(piecesImg = a.getImage(a.getCodeBase(), "pieces.gif"), 0);		// Start loading Images and wait for both to finish loading		try { tracker.waitForAll(); } catch (InterruptedException e) { ; }		// Get width and height of both Images, now that they're loaded		widthBoard = boardImg.getWidth(this);		heightBoard = boardImg.getHeight(this);		widthPieces = piecesImg.getWidth(this);		heightPieces = piecesImg.getHeight(this);		a.add(this);		reshape(x, y, width, height);		// Define the puzzle pieces		unit = heightPieces >> 2;		pieces[0] = new Piece(0, 0, 0, 0, 1, 2, unit);		pieces[1] = new Piece(0, 2, 1, 0, 1, 2, unit);		pieces[2] = new Piece(3, 0, 0, 2, 1, 2, unit);		pieces[3] = new Piece(3, 2, 1, 2, 1, 2, unit);		pieces[4] = new Piece(0, 4, 2, 0, 1, 1, unit);		pieces[5] = new Piece(1, 3, 2, 1, 1, 1, unit);		pieces[6] = new Piece(2, 3, 2, 2, 1, 1, unit);		pieces[7] = new Piece(3, 4, 2, 3, 1, 1, unit);		pieces[8] = new Piece(1, 2, 3, 2, 2, 1, unit);		pieces[9] = new Piece(1, 0, 3, 0, 2, 2, unit);		// Create offscreen buffer <width> pixels wide and <height> pixels tall		offscreenImage = createImage(width, height);		offscr = offscreenImage.getGraphics();		repaint();	}		public void pickPiece (int x, int y) {		int off = unit >> 1;		if (x >= off  &&  y >= off  &&  x < ((unit * 4) + off)  &&  y < ((unit * 5) + off)) {			x = (x - off) / unit;			y = (y - off) / unit;			for (int ii = 0; ii < pieces.length; ii++) {				if (pieces[ii].picks(x, y)) {					pickedPiece = pieces[ii];					pickedXoff = x - pickedPiece.xloc;					pickedYoff = y - pickedPiece.yloc;					pickedX = pickedPiece.xloc;					pickedY = pickedPiece.yloc;					return;				}			}		}		pickedPiece = null;	}		public void tryMove (int x, int y) {		pickedX += x;		pickedY += y;		x = pickedPiece.xloc + x;		y = pickedPiece.yloc + y;		if (pickedPiece.onBoard(x, y)) {			for (int ii = 0; ii < pieces.length; ii++) {				if (pickedPiece != pieces[ii]  &&  pieces[ii].intersects(pickedPiece, x, y))					return;			}			pickedPiece.moveTo(x, y);			repaint();		}	}		public void movePiece (int x, int y) {		int		dx, dy;		int 	off = unit >> 1;				if (pickedPiece != null) {			if (x >= off  &&  y >= off  &&  x < ((unit * 4) + off)  &&  y < ((unit * 5) + off)) {				x = ((x - off) / unit) - pickedXoff;				y = ((y - off) / unit) - pickedYoff;				while (pickedX != x  ||  pickedY != y) {					if (x > pickedX)						tryMove(1, 0);					else if (x < pickedX)						tryMove(-1, 0);					else if (y > pickedY)						tryMove(0, 1);					else						tryMove(0, -1);				}			}		}	}		public void paint (Graphics g) {		if (offscr != null) {			offscr.drawImage(boardImg, 0, 0, this);			for (int ii = 0; ii < pieces.length; ii++)				pieces[ii].drawPiece(offscr, piecesImg);			g.drawImage(offscreenImage, 0, 0, this);		}	}	public void update (Graphics g) {		paint(g);	}}public class Puzzle extends Applet {	private PuzzleBoard	slider;	public void init() {		super.init();		setLayout(null);		slider = new PuzzleBoard(0, 0, size().width, size().height, this);	}	public boolean mouseDown (Event evt, int x, int y) {		if (slider != null)			slider.pickPiece(x, y);		return true;	}		public boolean mouseDrag (Event evt, int x, int y) {		if (slider != null)			slider.movePiece(x, y);		return true;	}}