This class defines the user interface for a fine game of chess.

	events
	showMoves:from: showMovesAt:

	game callbacks
	addedPiece:at:white: completedMove:white: finishedGame: gameReset movedPiece:from:to: removedPiece:at: replacedPiece:with:at:white: undoMove:white: validateGamePosition

	geometry
	areasRemainingToFill: asSquare: atSquare: squaresDo:

	initialize
	addButtonRow addSquares buttonFillStyle buttonName:action: initialize newPiece:white: newSquare

	other stuff
	rotateBoard statusString

	playing
	autoPlay findBestMove movePieceFrom:to: newGame redoMove thinkAndMove undoMove

	stepping
	step stepTime

	parts bin
	descriptionForPartsBin

	drag and drop	top
	acceptDroppingMorph:event: This message is sent when a morph is dropped onto a morph that has agreed to accept the dropped morph by responding 'true' to the wantsDroppedMorph:Event: message. This default implementation just adds the given morph to the receiver.
	dragPiece:from:
	dragSquareEnter:from: Note: #wantsDroppedMorph: will validate move
	dragSquareLeave:from:
	wantsDroppedMorph:event: Return true if the receiver wishes to accept the given morph, which is being dropped by a hand in response to the given event. Note that for a successful drop operation both parties need to agree. The symmetric check is done automatically via aMorph wantsToBeDroppedInto: self.

	events	top
	showMoves:from:
	showMovesAt:

	game callbacks	top
	addedPiece:at:white:
	completedMove:white:
	finishedGame: 0 - white lost 0.5 - draw 1 - white won
	gameReset
	movedPiece:from:to:
	removedPiece:at:
	replacedPiece:with:at:white:
	undoMove:white:
	validateGamePosition This method does nothing but validating what you see (on screen) is what you get (from the board).

	geometry	top
	areasRemainingToFill: May be overridden by any subclasses with opaque regions
	asSquare:
	atSquare:
	squaresDo:

	initialize	top
	addButtonRow
	addSquares
	buttonFillStyle
	buttonName:action:
	initialize
	newPiece:white:
	newSquare

	other stuff	top
	rotateBoard
	statusString

	playing	top
	autoPlay
	findBestMove
	movePieceFrom:to:
	newGame
	redoMove Redo the last undone move
	thinkAndMove
	undoMove Undo the last move

	stepping	top
	step Do some periodic activity. Use startStepping/stopStepping to start and stop getting sent this message. The time between steps is specified by this morph's answer to the stepTime message. The generic version dispatches control to the player, if any. The nasty circumlocation about owner's transformation is necessitated by the flexing problem that the player remains in the properties dictionary both of the flex and the real morph. In the current architecture, only the top renderer's pointer to the player should actually be honored for the purpose of firing.
	stepTime Answer the desired time between steps in milliseconds. This default implementation requests that the 'step' method be called once every second.

	accessing	top
	blackBishopImage
	blackKingImage
	blackKnightImage
	blackPawnImage
	blackQueenImage
	blackRookImage
	whiteBishopImage
	whiteKingImage
	whiteKnightImage
	whitePawnImage
	whiteQueenImage
	whiteRookImage

	parts bin	top
	descriptionForPartsBin If the receiver is a member of a class that would like to be represented in a parts bin, answer the name by which it should be known, and a documentation string to be provided, for example, as balloon help. When the 'nativitySelector' is sent to the 'globalReceiver', it is expected that some kind of Morph will result. The parameters used in the implementation below are for documentation purposes only!