The IBoard interface is there just to show the point. Return board.GetPieceColor(toX, toY) = bishopColor There's a piece here: the move is valid only if we can capture If (board.IsEmpty(toX, toY)) return true // No piece: move is valid If(board.IsEmpty(x, y)) continue // No obstacles here: keep goingД®lse return false // Obstacle found before reaching target: the move is invalid Also validate if the coordinates are in the 0-7 range If (pathLength != Mathf.Abs(toY - fromY)) return false // Not diagonal public enum PieceColor Д«ool BishopCanMove(PieceColor bishopColor, int fromX, int fromY, int toX, int toY) I think the common way to do it would be checking if each cell on the path is empty or not. You need to take the board state into account for that. Move is valid if and only if X2=X1 and Y2-Y1=1 (only for a white Valid Pawn move, if the piece moves from (X1, Y1) to (X2, Y2), the Valid Knight move, if the piece moves from (X1, Y1) to (X2, Y2), the Valid Queen move, a queen's move is valid if it is either a valid Move is valid if and only if X2=X1 or Y2=Y1. Valid Rook move, if the piece moves from (X1, Y1) to (X2, Y2), the Move is valid if and only if |X2-X1|=|Y2-Y1|. Valid Bishop move, if the piece moves from (X1, Y1) to (X2, Y2), the Move is valid if and only if |X2-X1|<=1 and |Y2-Y1|<=1. Valid King move, if the piece moves from (X1, Y1) to (X2, Y2), the The simple algorithms I have for each piece are: The specific issue I am having is determining when a piece cannot move past a certain point because it is being blocked by a piece of its own colour or is able to take a piece of the opposite colour but cannot move past that point. I am trying to understand the algorithms behind determining valid moves for each chess piece.

List of chess piece moves