unfinished version of check

src/backend/Board.java

@@ -128,10 +128,11 @@ public class Board {
 
 	    // No piece selected yet
 	    if (selectedX == -1 && selectedY == -1) {
-	    	if (clickedPiece != null && clickedPiece.isWhite() == isTurnWhite()) {
+	    	if (clickedPiece != null && clickedPiece.isWhite() == isTurnWhite() && canSelectPieceWhenInCheck(x, y)){
                 selectedX = x;
                 selectedY = y;
                 calculateValidMoves(clickedPiece);
+                filterMovesForCheck();
             }
 	    } else {
 	        // Clicked the same piece again : unselect
@@ -482,4 +483,78 @@ public class Board {
 	        highlightedSquares[blackKing.getX()][blackKing.getY()] = true;
 	    }
 	} // check 
+	
+	public boolean canSelectPieceWhenInCheck(int x, int y) {
+	    Piece piece = board[x][y];
+	    
+	    // If no piece at this position or wrong color, can't select
+	    if (piece == null || piece.isWhite() != isTurnWhite()) {
+	        return false;
+	    }
+	    
+	    // If king is not in check, any piece can be selected
+	    if (!isKingInCheck(isTurnWhite())) {
+	        return true;
+	    }
+	    
+	    // When king is in check, check if this piece can make any legal move
+	    // that would get the king out of check
+	    ArrayList<Move> legalMoves = getLegalMoves(piece);
+	    for (Move move : legalMoves) {
+	        // Temporarily make the move
+	        Piece capturedPiece = board[move.getToX()][move.getToY()];
+	        board[move.getToX()][move.getToY()] = piece;
+	        board[move.getFromX()][move.getFromY()] = null;
+	        
+	        // Check if king is still in check after this move
+	        boolean stillInCheck = isKingInCheck(isTurnWhite());
+	        
+	        // Undo the move
+	        board[move.getFromX()][move.getFromY()] = piece;
+	        board[move.getToX()][move.getToY()] = capturedPiece;
+	        
+	        // If this move gets king out of check, piece can be selected
+	        if (!stillInCheck) {
+	            return true;
+	        }
+	    }
+	    
+	    // No legal moves that get king out of check
+	    return false;
+	}
+	
+	private void filterMovesForCheck() {
+	    if (!isKingInCheck(isTurnWhite())) {
+	        return; // No filtering needed if not in check
+	    }
+	    
+	    Piece selectedPiece = board[selectedX][selectedY];
+	    boolean[][] newHighlights = new boolean[width][height];
+	    
+	    for (int y = 0; y < height; y++) {
+	        for (int x = 0; x < width; x++) {
+	            if (highlightedSquares[x][y]) {
+	                // Temporarily make the move
+	                Piece capturedPiece = board[x][y];
+	                board[x][y] = selectedPiece;
+	                board[selectedX][selectedY] = null;
+	                
+	                // Check if king is still in check
+	                boolean stillInCheck = isKingInCheck(isTurnWhite());
+	                
+	                // Undo the move
+	                board[selectedX][selectedY] = selectedPiece;
+	                board[x][y] = capturedPiece;
+	                
+	                // Only keep highlights for moves that get out of check
+	                if (!stillInCheck) {
+	                    newHighlights[x][y] = true;
+	                }
+	            }
+	        }
+	    }
+	    
+	    // Replace highlights with filtered version
+	    highlightedSquares = newHighlights;
+	}
 }