Some things.

chess/src/chess/Board.java

@@ -1,6 +1,8 @@
 package chess;
 
 import java.awt.Color;
+import java.awt.Rectangle;
+import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.Map;
 import javalib.impworld.WorldScene;
@@ -11,8 +13,12 @@ import javalib.worldimages.RectangleImage;
 
 class Board {
     Map<Coord, Piece> board;
+    Map<Coord, Info> info;
 
-    Board() { this.board = new HashMap<Coord, Piece>(); }
+    Board() {
+        this.board = new HashMap<Coord, Piece>();
+        this.info = new HashMap<Coord, Info>();
+    }
 
     WorldScene draw() {
         WorldScene scene = new WorldScene(Util.size, Util.size);
@@ -21,11 +27,19 @@ class Board {
                 Piece piece = this.board.get(new Coord(i, j));
                 scene.placeImageXY(
                     new OverlayImage(
-                        (piece == null) ? new EmptyImage() : piece.draw(),
+                        (this.info.get(new Coord(i, j)) != null)
-                        new RectangleImage(
+                            ? new RectangleImage(
-                            Util.scale, Util.scale, OutlineMode.SOLID,
+                                  Util.scale, Util.scale, OutlineMode.SOLID,
-                            (i + j) % 2 == 0 ? Color.DARK_GRAY
+                                  new Color(0, 200, 200, 150)
-                                             : Color.LIGHT_GRAY
+                              )
+                            : new EmptyImage(),
+                        new OverlayImage(
+                            (piece == null) ? new EmptyImage() : piece.draw(),
+                            new RectangleImage(
+                                Util.scale, Util.scale, OutlineMode.SOLID,
+                                (i + j) % 2 == 0 ? Color.DARK_GRAY
+                                                 : Color.LIGHT_GRAY
+                            )
                         )
                     ),
                     i * Util.scale + Util.halfScale,
@@ -40,14 +54,34 @@ class Board {
     Piece get(Coord coord) { return this.board.get(coord); }
     void drop(Coord coord) { this.board.remove(coord); }
 
+    // Show the moves a piece can take.
+    void displayMoves(Coord coord) {
+        ArrayList<Coord> moves = this.get(coord).moves(coord);
+        for (Coord move : moves) this.info.put(move, Info.CANMOVE);
+    }
+
     // Move a piece.
     void move(Coord targ, Coord dest) {
         Piece piece = this.get(targ);
         this.drop(targ);
         this.set(dest, piece);
     }
+
+    // Get the valid moves for a piece.
+    ArrayList<Coord> getMoves(Coord coord) {
+        Piece piece = this.get(coord);
+
+        // If not the active actor, no moves possible and so return empty list.
+        // if (!piece.col.equals(this.activeActor.col))
+        //    return new ArrayList<Coord>();
+
+        return piece.moves(coord);
+    }
 }
 
+// Information layered over the board.
+enum Info { CANMOVE, WARN }
+
 // Measured from top left.
 class Coord {
     int x, y;

chess/src/chess/Game.java

@@ -19,10 +19,8 @@ class Game extends World {
 
     Game() {
         this.board = new Board();
-
         this.white = new Player(Util.Col.WHITE, this.board);
         this.black = new Player(Util.Col.BLACK, this.board);
-
         this.activeActor = this.white;
 
         this.setup();

chess/src/chess/Main.java

@@ -1,9 +1,13 @@
 package chess;
 
+import chess.Util.Col;
 import tester.Tester;
 
 class Examples {
-    void testItAll(Tester t) { new Game().run(); }
+    void testItAll(Tester t) {
+        Game game = new Game();
+        game.run();
+    }
 
     void testCoord(Tester t) {
         Coord coord = new Coord(1, 1);
@@ -14,11 +18,4 @@ class Examples {
         t.checkExpect(coord.hashCode() == cod.hashCode(), true);
         t.checkExpect(coord.hashCode() == cor.hashCode(), false);
     }
-
-    void testBoard(Tester t) {
-        Piece pawn = new Pawn(Util.Col.BLACK);
-        Board board = new Board();
-        board.set(new Coord(0, 0), pawn);
-        t.checkExpect(board.get(new Coord(0, 0)), pawn);
-    }
 }

chess/src/chess/Piece.java

@@ -1,5 +1,7 @@
 package chess;
 
+import chess.Util.Col;
+import java.util.ArrayList;
 import javalib.worldimages.*;
 
 // The piece types.
@@ -16,6 +18,9 @@ abstract class Piece {
     }
 
     WorldImage draw() { return new EmptyImage(); };
+
+    // Return list of possible move locations, centered around the given coord.
+    ArrayList<Coord> moves(Coord coord) { return new ArrayList<Coord>(); }
 }
 
 class Pawn extends Piece {
@@ -26,6 +31,14 @@ class Pawn extends Piece {
             "Pawn.png"
         );
     }
+
+    ArrayList<Coord> moves(Coord coord) {
+        ArrayList<Coord> moves = new ArrayList<Coord>();
+        moves.add(
+            new Coord(coord.x, coord.y + (this.col.equals(Col.BLACK) ? 1 : -1))
+        );
+        return moves;
+    }
 }
 
 class Rook extends Piece {
@@ -36,6 +49,13 @@ class Rook extends Piece {
             "Rook.png"
         );
     }
+
+    ArrayList<Coord> moves(Coord coord) {
+        ArrayList<Coord> moves = new ArrayList<Coord>();
+        for (int i = -7; i < 8; i++) moves.add(new Coord(coord.x, coord.y + i));
+        for (int i = -7; i < 8; i++) moves.add(new Coord(coord.x + i, coord.y));
+        return moves;
+    }
 }
 
 class Knight extends Piece {
@@ -46,6 +66,21 @@ class Knight extends Piece {
             "Knight.png"
         );
     }
+
+    ArrayList<Coord> moves(Coord coord) {
+        ArrayList<Coord> moves = new ArrayList<Coord>();
+        moves.add(new Coord(coord.x + 1, coord.y + 2));
+        moves.add(new Coord(coord.x + 2, coord.y + 1));
+        moves.add(new Coord(coord.x + 1, coord.y - 2));
+        moves.add(new Coord(coord.x + 2, coord.y - 1));
+        moves.add(new Coord(coord.x - 1, coord.y - 2));
+        moves.add(new Coord(coord.x - 2, coord.y - 1));
+        moves.add(new Coord(coord.x - 1, coord.y + 2));
+        moves.add(new Coord(coord.x - 2, coord.y + 1));
+        moves.add(new Coord(coord.x - 1, coord.y - 2));
+        moves.add(new Coord(coord.x - 2, coord.y - 1));
+        return moves;
+    }
 }
 
 class Bishop extends Piece {

chess/src/chess/Player.java

@@ -4,5 +4,5 @@ package chess;
 class Player extends Actor {
     Player(Util.Col col, Board board) { super(col, board); }
 
-    void click(Coord coord) { this.board.move(coord, new Coord(4, 4)); }
+    void click(Coord coord) { this.board.displayMoves(coord); }
 }