diff --git a/Day 42 (object oriented design)/notes.txt b/Day 42 (object oriented design)/notes.txt
index 30ce94d..870f77c 100644
--- a/Day 42 (object oriented design)/notes.txt	
+++ b/Day 42 (object oriented design)/notes.txt	
@@ -15,3 +15,11 @@ Designing good classes
 * Do not repeat data unless truly necessary.
 
 * Do not give variables more scope than they require.
+
+Immutable objects
+-----------------
+Benefits:
+	Thread-safe
+	Can freely share pointers to objects; no hidden side effects if something changes
+Drawback:
+	If there are lots of changes then immutability may result in memory burn and slowdowns
diff --git a/Day 43, 45, 46 (chess application design)/Chess.class b/Day 43, 45, 46 (chess application design)/Chess.class
new file mode 100644
index 0000000..00d69e0
Binary files /dev/null and b/Day 43, 45, 46 (chess application design)/Chess.class differ
diff --git a/Day 43, 45, 46 (chess application design)/Chess.java b/Day 43, 45, 46 (chess application design)/Chess.java
index fc282d7..a5f6622 100644
--- a/Day 43, 45, 46 (chess application design)/Chess.java	
+++ b/Day 43, 45, 46 (chess application design)/Chess.java	
@@ -1,55 +1,168 @@
+import java.util.*;
+
+import javafx.application.*;
+import javafx.stage.*;
+import javafx.scene.*;
+import javafx.scene.control.*;
+import javafx.scene.canvas.*;
+import javafx.scene.shape.*;
+import javafx.scene.layout.*;
+import javafx.scene.paint.*;
+import javafx.scene.text.*;
+import javafx.event.*;
+import javafx.scene.input.*;
+import javafx.scene.image.*;
+import javafx.geometry.*;
 
 //Main class and GUI
 
-public class Chess {
-	private GameBoard board;
+public class Chess extends Application {
+	private ArrayList<GameState> gameStateHistory; //Stack of GameBoard states for the move undo.
+	private ArrayList<Move> moveHistory;  //Stack of tuples (moves) so they can be displayed.
+	private ArrayList<String> moveNotationHistory;  //Stack of move notations.
 
 	//User's first click for a move.
 	private Integer clickRow;  //null means no first click made currently.
 	private Integer clickColumn;
 
-	private ArrayList<GameState> gameStateHistory; //Stack of GameBoard states for the move undo.
-	private ArrayList<Move> moveHistory;  //Stack of tuples (moves) so they can be displayed.
-	private ArrayList<String> moveNotationHistory;  //Stack of move notations.
+	private GraphicsContext graphics;
+	private TextArea moveHistoryTextArea;
+
+	//Load images
+	private static final Image W_ROOK = new Image("img/w_rook_png_shadow_128px.png");
+	private static final Image B_ROOK = new Image("img/b_rook_png_shadow_128px.png");
+	private static final Image W_KNIGHT = new Image("img/w_knight_png_shadow_128px.png");
+	private static final Image B_KNIGHT = new Image("img/b_knight_png_shadow_128px.png");
+	private static final Image W_BISHOP = new Image("img/w_bishop_png_shadow_128px.png");
+	private static final Image B_BISHOP = new Image("img/b_bishop_png_shadow_128px.png");
+	private static final Image W_QUEEN = new Image("img/w_queen_png_shadow_128px.png");
+	private static final Image B_QUEEN = new Image("img/b_queen_png_shadow_128px.png");
+	private static final Image W_KING = new Image("img/w_king_png_shadow_128px.png");
+	private static final Image B_KING = new Image("img/b_king_png_shadow_128px.png");
+	private static final Image W_PAWN = new Image("img/w_pawn_png_shadow_128px.png");
+	private static final Image B_PAWN = new Image("img/b_pawn_png_shadow_128px.png");
+
+	public static void main(String[] args) {
+		launch(args);
+	}
+
+	public void start(Stage stage) {
+		//Boilerplate code
+		VBox root = new VBox();
+		Scene scene = new Scene(root);
+		stage.setTitle("Chess");
+		stage.setScene(scene);
+
+		//Set up canvas for the board
+		Canvas board = new Canvas(400, 400);
+		graphics = board.getGraphicsContext2D();
+
+		//Setup move history text area
+		moveHistoryTextArea = new TextArea();
+		moveHistoryTextArea.setFont(Font.font("Courier New", FontWeight.BOLD, 12));
+		moveHistoryTextArea.setPrefColumnCount("129. b1Rxb8R+ a1Rxa8R++".length());
+		moveHistoryTextArea.setEditable(false);
+		moveHistoryTextArea.setPrefHeight(400);
+		moveHistoryTextArea.setMinHeight(400);
+		moveHistoryTextArea.setMaxHeight(400);
+
+		//Horizontal box for board and move history text area
+		HBox hb = new HBox(20, board, moveHistoryTextArea);
+		hb.setAlignment(Pos.CENTER);
+		root.getChildren().add(hb);
+
+		//Set up buttons
+		Button undo = new Button("Undo");
+		Button reset = new Button("Reset");
+		Button aiMove = new Button("AI move");
+		HBox h = new HBox(20, undo, reset, aiMove);
+		h.setAlignment(Pos.CENTER);
+		h.setPadding(new Insets(10,10,10,10));
+		root.getChildren().add(h);
 
-	public void start() {
-		//Set up graphics on the screen, buttons
-		//Set up the initial board
 		//Set up empty move history, game history,  notation history.
-		//clickRow and clickCol are null
+		gameStateHistory = new ArrayList<GameState>();
+		gameStateHistory.add(new GameState()); //Set up the initial board
+		moveHistory = new ArrayList<Move>();
+		moveNotationHistory = new ArrayList<String>();
+
+		//No clicks yet
+		clickRow = clickColumn = null;
+
 		//Set up mouse/click events
+		board.setOnMousePressed(this::mouseClick);
+		undo.setOnMousePressed(this::undo);
+		reset.setOnMousePressed(this::reset);
+		aiMove.setOnMousePressed(this::moveAI);
+
+		//Refresh the board
+		paintBoard();
+
+		//Fix mysterious broken width and prevent shrinking window
+		stage.setWidth(664);
+		stage.setMinWidth(stage.getWidth());
+		stage.setMinHeight(stage.getHeight());
+
+		stage.show();
+	}
+
+	private void paintBoard() {
+		for(int x = 0; x < 8; x++) {
+			for(int y = 0; y < 8; y++) {
+				graphics.setFill((x + y) % 2 == 0 ? Color.BURLYWOOD : Color.FORESTGREEN);
+				graphics.fillRect(50*x, 50*y, 50, 50);
+				Square s = board().getSquare(x, y);
+				if ( s.getType() ==  Square.PAWN && s.isWhite()) graphics.drawImage(W_PAWN, 50*x, 50*y, 50, 50);
+				if ( s.getType() ==  Square.PAWN && !s.isWhite()) graphics.drawImage(B_PAWN, 50*x, 50*y, 50, 50);
+				if ( s.getType() ==  Square.KNIGHT && s.isWhite()) graphics.drawImage(W_KNIGHT, 50*x, 50*y, 50, 50);
+				if ( s.getType() ==  Square.KNIGHT && !s.isWhite()) graphics.drawImage(B_KNIGHT, 50*x, 50*y, 50, 50);
+				if ( s.getType() ==  Square.BISHOP && s.isWhite()) graphics.drawImage(W_BISHOP, 50*x, 50*y, 50, 50);
+				if ( s.getType() ==  Square.BISHOP && !s.isWhite()) graphics.drawImage(B_BISHOP, 50*x, 50*y, 50, 50);
+				if ( s.getType() ==  Square.ROOK && s.isWhite()) graphics.drawImage(W_ROOK, 50*x, 50*y, 50, 50);
+				if ( s.getType() ==  Square.ROOK && !s.isWhite()) graphics.drawImage(B_ROOK, 50*x, 50*y, 50, 50);
+				if ( s.getType() ==  Square.QUEEN && s.isWhite()) graphics.drawImage(W_QUEEN, 50*x, 50*y, 50, 50);
+				if ( s.getType() ==  Square.QUEEN && !s.isWhite()) graphics.drawImage(B_QUEEN, 50*x, 50*y, 50, 50);
+				if ( s.getType() ==  Square.KING && s.isWhite()) graphics.drawImage(W_KING, 50*x, 50*y, 50, 50);
+				if ( s.getType() ==  Square.KING && !s.isWhite()) graphics.drawImage(B_KING, 50*x, 50*y, 50, 50);
+			}
+		}
+	}
+
+	private GameState board() {
+		return gameStateHistory.get(gameStateHistory.size()-1);
 	}
 
 	//Reset to the intial game position.
-	public void reset() {
+	public void reset(MouseEvent e) {
 		//Set up the initial board
 		//Clear out clickRo and clickCol
 		//Clera out all the histories.
+
 	}
 
 	//AI makes a move
-	public void moveAI() {
+	public void moveAI(MouseEvent e) {
 		//Ask the gameState for a list of all legal moves.
 		//Get one of those in the list uniformly at random.
-		makeMove(...);
+//		makeMove(...);
 	}
 
-	private void makeMove(...) {
+	private void makeMove(Move move) {
 		//Clone the gameState object for the current state of the game, tell it to make the move, add it to the move history
 		//add the notation for it
 		//add the move to the history as well
 	}
 
 	//For the human moving
-	public void mouseClick() {
+	public void mouseClick(MouseEvent e) {
 		//If it is the first click (null check) then record it, updtae the GUI to show highlighting
 		//else attempt the move:
 
-		makeMove(...);
+//		makeMove(...);
 	}
 
 	//Undo button for the most recent move
-	public void undo() {
+	public void undo(MouseEvent e) {
 		//Pop those 3 history object things and update the GUI.
 	}
 
diff --git a/Day 43, 45, 46 (chess application design)/GameState.class b/Day 43, 45, 46 (chess application design)/GameState.class
new file mode 100644
index 0000000..a694af1
Binary files /dev/null and b/Day 43, 45, 46 (chess application design)/GameState.class differ
diff --git a/Day 43, 45, 46 (chess application design)/GameState.java b/Day 43, 45, 46 (chess application design)/GameState.java
index 913398e..0dcdd84 100644
--- a/Day 43, 45, 46 (chess application design)/GameState.java	
+++ b/Day 43, 45, 46 (chess application design)/GameState.java	
@@ -8,19 +8,45 @@ public class GameState {
 
 	public GameState() {
 		//Set turn to white
+		isWhitesTurn = true;
+
 		//Initialize squares with legal starting position.
+		boardSquares = new Square[] {
+			new Square(Square.OUT_OF_BOUNDS), new Square(Square.OUT_OF_BOUNDS), new Square(Square.OUT_OF_BOUNDS), new Square(Square.OUT_OF_BOUNDS), new Square(Square.OUT_OF_BOUNDS), new Square(Square.OUT_OF_BOUNDS), new Square(Square.OUT_OF_BOUNDS), new Square(Square.OUT_OF_BOUNDS), new Square(Square.OUT_OF_BOUNDS), new Square(Square.OUT_OF_BOUNDS), new Square(Square.OUT_OF_BOUNDS), new Square(Square.OUT_OF_BOUNDS),
+			new Square(Square.OUT_OF_BOUNDS), new Square(Square.OUT_OF_BOUNDS), new Square(Square.OUT_OF_BOUNDS), new Square(Square.OUT_OF_BOUNDS), new Square(Square.OUT_OF_BOUNDS), new Square(Square.OUT_OF_BOUNDS), new Square(Square.OUT_OF_BOUNDS), new Square(Square.OUT_OF_BOUNDS), new Square(Square.OUT_OF_BOUNDS), new Square(Square.OUT_OF_BOUNDS), new Square(Square.OUT_OF_BOUNDS), new Square(Square.OUT_OF_BOUNDS),
+			new Square(Square.OUT_OF_BOUNDS), new Square(Square.OUT_OF_BOUNDS), new Square(Square.ROOK, true), new Square(Square.KNIGHT, true), new Square(Square.BISHOP, true), new Square(Square.QUEEN, true), new Square(Square.KING, true), new Square(Square.BISHOP, true), new Square(Square.KNIGHT, true), new Square(Square.ROOK, true), new Square(Square.OUT_OF_BOUNDS), new Square(Square.OUT_OF_BOUNDS),  //white
+			new Square(Square.OUT_OF_BOUNDS), new Square(Square.OUT_OF_BOUNDS), new Square(Square.PAWN, true), new Square(Square.PAWN, true), new Square(Square.PAWN, true), new Square(Square.PAWN, true), new Square(Square.PAWN, true), new Square(Square.PAWN, true), new Square(Square.PAWN, true), new Square(Square.PAWN, true), new Square(Square.OUT_OF_BOUNDS), new Square(Square.OUT_OF_BOUNDS), //white pawns
+
+			new Square(Square.OUT_OF_BOUNDS), new Square(Square.OUT_OF_BOUNDS), new Square(Square.EMPTY), new Square(Square.EMPTY), new Square(Square.EMPTY), new Square(Square.EMPTY), new Square(Square.EMPTY), new Square(Square.EMPTY), new Square(Square.EMPTY), new Square(Square.EMPTY), new Square(Square.OUT_OF_BOUNDS), new Square(Square.OUT_OF_BOUNDS),
+			new Square(Square.OUT_OF_BOUNDS), new Square(Square.OUT_OF_BOUNDS), new Square(Square.EMPTY), new Square(Square.EMPTY), new Square(Square.EMPTY), new Square(Square.EMPTY), new Square(Square.EMPTY), new Square(Square.EMPTY), new Square(Square.EMPTY), new Square(Square.EMPTY), new Square(Square.OUT_OF_BOUNDS), new Square(Square.OUT_OF_BOUNDS),
+			new Square(Square.OUT_OF_BOUNDS), new Square(Square.OUT_OF_BOUNDS), new Square(Square.EMPTY), new Square(Square.EMPTY), new Square(Square.EMPTY), new Square(Square.EMPTY), new Square(Square.EMPTY), new Square(Square.EMPTY), new Square(Square.EMPTY), new Square(Square.EMPTY), new Square(Square.OUT_OF_BOUNDS), new Square(Square.OUT_OF_BOUNDS),
+			new Square(Square.OUT_OF_BOUNDS), new Square(Square.OUT_OF_BOUNDS), new Square(Square.EMPTY), new Square(Square.EMPTY), new Square(Square.EMPTY), new Square(Square.EMPTY), new Square(Square.EMPTY), new Square(Square.EMPTY), new Square(Square.EMPTY), new Square(Square.EMPTY), new Square(Square.OUT_OF_BOUNDS), new Square(Square.OUT_OF_BOUNDS),
+
+			new Square(Square.OUT_OF_BOUNDS), new Square(Square.OUT_OF_BOUNDS), new Square(Square.PAWN, false), new Square(Square.PAWN, false), new Square(Square.PAWN, false), new Square(Square.PAWN, false), new Square(Square.PAWN, false), new Square(Square.PAWN, false), new Square(Square.PAWN, false), new Square(Square.PAWN, false), new Square(Square.OUT_OF_BOUNDS), new Square(Square.OUT_OF_BOUNDS), //white pawns
+			new Square(Square.OUT_OF_BOUNDS), new Square(Square.OUT_OF_BOUNDS), new Square(Square.ROOK, false), new Square(Square.KNIGHT, false), new Square(Square.BISHOP, false), new Square(Square.QUEEN, false), new Square(Square.KING, false), new Square(Square.BISHOP, false), new Square(Square.KNIGHT, false), new Square(Square.ROOK, false), new Square(Square.OUT_OF_BOUNDS), new Square(Square.OUT_OF_BOUNDS),  //black
+			new Square(Square.OUT_OF_BOUNDS), new Square(Square.OUT_OF_BOUNDS), new Square(Square.OUT_OF_BOUNDS), new Square(Square.OUT_OF_BOUNDS), new Square(Square.OUT_OF_BOUNDS), new Square(Square.OUT_OF_BOUNDS), new Square(Square.OUT_OF_BOUNDS), new Square(Square.OUT_OF_BOUNDS), new Square(Square.OUT_OF_BOUNDS), new Square(Square.OUT_OF_BOUNDS), new Square(Square.OUT_OF_BOUNDS), new Square(Square.OUT_OF_BOUNDS),
+			new Square(Square.OUT_OF_BOUNDS), new Square(Square.OUT_OF_BOUNDS), new Square(Square.OUT_OF_BOUNDS), new Square(Square.OUT_OF_BOUNDS), new Square(Square.OUT_OF_BOUNDS), new Square(Square.OUT_OF_BOUNDS), new Square(Square.OUT_OF_BOUNDS), new Square(Square.OUT_OF_BOUNDS), new Square(Square.OUT_OF_BOUNDS), new Square(Square.OUT_OF_BOUNDS), new Square(Square.OUT_OF_BOUNDS), new Square(Square.OUT_OF_BOUNDS),
+		};
+
 	}
 
-	public GameState attemptMove(Move m) {
-		//See if it is legal.
-		//Change the board state accordingly.
+	// zero-based index for col and row.  Note that -1 and -2 are valid indices into the array, just OUT_OF_BOUNDS.
+	public Square getSquare(int col, int row) {
+		return boardSquares[12*2 + 2 + col + row * 12];
 	}
 
-	public Moves[] getAllPossibleMoves() {
+	public GameState getStateAfterMove(Move m) {
+		//See if it is legal.  If not, return null.
+		//Create a new object based on this one, update the board state accordingly.
+		return null;
+	}
+
+	public Move[] getAllPossibleMoves() {
+		return null;
 	}
 
 	// returns something like "checkmate", "stalemate", etc.
 	public String getFeedback() {
+		return null;
 	}
-
 }
diff --git a/Day 43, 45, 46 (chess application design)/Move.class b/Day 43, 45, 46 (chess application design)/Move.class
new file mode 100644
index 0000000..42b46f1
Binary files /dev/null and b/Day 43, 45, 46 (chess application design)/Move.class differ
diff --git a/Day 43, 45, 46 (chess application design)/Move.java b/Day 43, 45, 46 (chess application design)/Move.java
index 59c84fe..cd00174 100644
--- a/Day 43, 45, 46 (chess application design)/Move.java	
+++ b/Day 43, 45, 46 (chess application design)/Move.java	
@@ -2,12 +2,13 @@
 public class Move {
 	//source and dest coordinates
 
-	public Move(...source...dest...) {
+	public Move(int sourceRow, int sourceColumn, int destinationRow, int destinationColumn) {
 	}
 
 
 	//returns something like e2-e4 or Qc8++
 	public String toString() {
+		return "";
 	}
 
 }
diff --git a/Day 43, 45, 46 (chess application design)/Square.class b/Day 43, 45, 46 (chess application design)/Square.class
new file mode 100644
index 0000000..937a38a
Binary files /dev/null and b/Day 43, 45, 46 (chess application design)/Square.class differ
diff --git a/Day 43, 45, 46 (chess application design)/Square.java b/Day 43, 45, 46 (chess application design)/Square.java
index 42fbc2c..5a4bae5 100644
--- a/Day 43, 45, 46 (chess application design)/Square.java	
+++ b/Day 43, 45, 46 (chess application design)/Square.java	
@@ -1,12 +1,42 @@
 
 public class Square {
 	//Pawn, knight, bishop, rook, queen, king, blank.
-	//White or black boolean
+	public static final int OUT_OF_BOUNDS = -1;
+	public static final int EMPTY = 0;
+	public static final int PAWN = 1;
+	public static final int KNIGHT = 2;
+	public static final int BISHOP = 3;
+	public static final int ROOK = 4;
+	public static final int QUEEN = 5;
+	public static final int KING = 6;
+
+	private int type; //one of the 8 constants above.
+	private boolean isWhite;
+
 	//en passant boolean flag (for the square that would be "captured")
 	//boolean Knowledge of whether or not this piece moved yet (for castling)
 	//boolean for off-the-board square
 
+	public Square(int type) {
+		this(type, false);
+	}
+
+	public Square(int type, boolean isWhite) {
+		this.type = type;
+		this.isWhite = isWhite;
+	}
+
 	//Positive values for white, negative for black, blank square is 0.
 	public int getValue() {
+		return 0; //TODO.
 	}
+
+	public int getType() {
+		return type;
+	}
+
+	public boolean isWhite() {
+		return isWhite;
+	}
+
 }
\ No newline at end of file
diff --git a/Day 43, 45, 46 (chess application design)/img/Image license copyright notice.txt b/Day 43, 45, 46 (chess application design)/img/Image license copyright notice.txt
new file mode 100644
index 0000000..481325c
--- /dev/null
+++ b/Day 43, 45, 46 (chess application design)/img/Image license copyright notice.txt	
@@ -0,0 +1,14 @@
+These chess images are from https://opengameart.org/content/chess-pieces-and-board-squares by JohnPablok and are licensed under CC-BY-SA 3.0: https://creativecommons.org/licenses/by-sa/3.0/
+
+ You are free to:
+
+    Share — copy and redistribute the material in any medium or format for any purpose, even commercially.
+    Adapt — remix, transform, and build upon the material for any purpose, even commercially.
+    The licensor cannot revoke these freedoms as long as you follow the license terms.
+
+Under the following terms:
+
+    Attribution — You must give appropriate credit , provide a link to the license, and indicate if changes were made . You may do so in any reasonable manner, but not in any way that suggests the licensor endorses you or your use.
+    ShareAlike — If you remix, transform, or build upon the material, you must distribute your contributions under the same license as the original.
+    No additional restrictions — You may not apply legal terms or technological measures that legally restrict others from doing anything the license permits.
+
diff --git a/Day 43, 45, 46 (chess application design)/img/JohnPablok Cburnett Chess Zip.zip b/Day 43, 45, 46 (chess application design)/img/JohnPablok Cburnett Chess Zip.zip
new file mode 100644
index 0000000..8149c4f
Binary files /dev/null and b/Day 43, 45, 46 (chess application design)/img/JohnPablok Cburnett Chess Zip.zip differ
diff --git a/Day 43, 45, 46 (chess application design)/img/b_bishop_png_shadow_128px.png b/Day 43, 45, 46 (chess application design)/img/b_bishop_png_shadow_128px.png
new file mode 100644
index 0000000..f226973
Binary files /dev/null and b/Day 43, 45, 46 (chess application design)/img/b_bishop_png_shadow_128px.png differ
diff --git a/Day 43, 45, 46 (chess application design)/img/b_king_png_shadow_128px.png b/Day 43, 45, 46 (chess application design)/img/b_king_png_shadow_128px.png
new file mode 100644
index 0000000..c4d9c31
Binary files /dev/null and b/Day 43, 45, 46 (chess application design)/img/b_king_png_shadow_128px.png differ
diff --git a/Day 43, 45, 46 (chess application design)/img/b_knight_png_shadow_128px.png b/Day 43, 45, 46 (chess application design)/img/b_knight_png_shadow_128px.png
new file mode 100644
index 0000000..99cc17b
Binary files /dev/null and b/Day 43, 45, 46 (chess application design)/img/b_knight_png_shadow_128px.png differ
diff --git a/Day 43, 45, 46 (chess application design)/img/b_pawn_png_shadow_128px.png b/Day 43, 45, 46 (chess application design)/img/b_pawn_png_shadow_128px.png
new file mode 100644
index 0000000..3761321
Binary files /dev/null and b/Day 43, 45, 46 (chess application design)/img/b_pawn_png_shadow_128px.png differ
diff --git a/Day 43, 45, 46 (chess application design)/img/b_queen_png_shadow_128px.png b/Day 43, 45, 46 (chess application design)/img/b_queen_png_shadow_128px.png
new file mode 100644
index 0000000..5c2c64a
Binary files /dev/null and b/Day 43, 45, 46 (chess application design)/img/b_queen_png_shadow_128px.png differ
diff --git a/Day 43, 45, 46 (chess application design)/img/b_rook_png_shadow_128px.png b/Day 43, 45, 46 (chess application design)/img/b_rook_png_shadow_128px.png
new file mode 100644
index 0000000..4ab37ab
Binary files /dev/null and b/Day 43, 45, 46 (chess application design)/img/b_rook_png_shadow_128px.png differ
diff --git a/Day 43, 45, 46 (chess application design)/img/square brown dark_png_shadow_128px.png b/Day 43, 45, 46 (chess application design)/img/square brown dark_png_shadow_128px.png
new file mode 100644
index 0000000..9603b48
Binary files /dev/null and b/Day 43, 45, 46 (chess application design)/img/square brown dark_png_shadow_128px.png differ
diff --git a/Day 43, 45, 46 (chess application design)/img/square brown light_png_shadow_128px.png b/Day 43, 45, 46 (chess application design)/img/square brown light_png_shadow_128px.png
new file mode 100644
index 0000000..82c7c16
Binary files /dev/null and b/Day 43, 45, 46 (chess application design)/img/square brown light_png_shadow_128px.png differ
diff --git a/Day 43, 45, 46 (chess application design)/img/square gray dark _png_shadow_128px.png b/Day 43, 45, 46 (chess application design)/img/square gray dark _png_shadow_128px.png
new file mode 100644
index 0000000..827c51b
Binary files /dev/null and b/Day 43, 45, 46 (chess application design)/img/square gray dark _png_shadow_128px.png differ
diff --git a/Day 43, 45, 46 (chess application design)/img/square gray light _png_shadow_128px.png b/Day 43, 45, 46 (chess application design)/img/square gray light _png_shadow_128px.png
new file mode 100644
index 0000000..8ee1a45
Binary files /dev/null and b/Day 43, 45, 46 (chess application design)/img/square gray light _png_shadow_128px.png differ
diff --git a/Day 43, 45, 46 (chess application design)/img/w_bishop_png_shadow_128px.png b/Day 43, 45, 46 (chess application design)/img/w_bishop_png_shadow_128px.png
new file mode 100644
index 0000000..4cee395
Binary files /dev/null and b/Day 43, 45, 46 (chess application design)/img/w_bishop_png_shadow_128px.png differ
diff --git a/Day 43, 45, 46 (chess application design)/img/w_king_png_shadow_128px.png b/Day 43, 45, 46 (chess application design)/img/w_king_png_shadow_128px.png
new file mode 100644
index 0000000..fe0b533
Binary files /dev/null and b/Day 43, 45, 46 (chess application design)/img/w_king_png_shadow_128px.png differ
diff --git a/Day 43, 45, 46 (chess application design)/img/w_knight_png_shadow_128px.png b/Day 43, 45, 46 (chess application design)/img/w_knight_png_shadow_128px.png
new file mode 100644
index 0000000..4b71788
Binary files /dev/null and b/Day 43, 45, 46 (chess application design)/img/w_knight_png_shadow_128px.png differ
diff --git a/Day 43, 45, 46 (chess application design)/img/w_pawn_png_shadow_128px.png b/Day 43, 45, 46 (chess application design)/img/w_pawn_png_shadow_128px.png
new file mode 100644
index 0000000..d79f4fc
Binary files /dev/null and b/Day 43, 45, 46 (chess application design)/img/w_pawn_png_shadow_128px.png differ
diff --git a/Day 43, 45, 46 (chess application design)/img/w_queen_png_shadow_128px.png b/Day 43, 45, 46 (chess application design)/img/w_queen_png_shadow_128px.png
new file mode 100644
index 0000000..66aa523
Binary files /dev/null and b/Day 43, 45, 46 (chess application design)/img/w_queen_png_shadow_128px.png differ
diff --git a/Day 43, 45, 46 (chess application design)/img/w_rook_png_shadow_128px.png b/Day 43, 45, 46 (chess application design)/img/w_rook_png_shadow_128px.png
new file mode 100644
index 0000000..7d9e2ea
Binary files /dev/null and b/Day 43, 45, 46 (chess application design)/img/w_rook_png_shadow_128px.png differ
diff --git a/Day 43, 45, 46 (chess application design)/writing good methods.txt b/Day 43, 45, 46 (chess application design)/writing good methods.txt
new file mode 100644
index 0000000..f934ded
--- /dev/null
+++ b/Day 43, 45, 46 (chess application design)/writing good methods.txt	
@@ -0,0 +1,22 @@
+
+Writing good methods/functions:
+	* Naming
+		* Give descriptive names that say exactly what the routine does (usually verb-noun)
+		* The name should include or imply the return type
+	* Lines of code
+		* Functions over a couple hundred lines of code tend to be more error-prone
+		* Otherwise, no hard constraints on method length - whatever is natural for the situation
+	* Parameters
+		* Use parameter order consistently among different functions
+		* Document assumptions on parameters
+		* Document units
+		* Document zero-based-counting vs one-based-counting if not obvious
+	* Error handling
+		* Check values of input parameters
+		* Use assertions to check for bugs.  Use error handling to check for bad input.
+		* Techniques for error handling:
+			* Return null or neutral value
+			* Print or log the error and continue execution
+			* Throw an exception/error
+			* Terminate the program
+