Chess Loop Builder

Your task is to write a function that places chess pieces (Knights, Bishops, Rooks, Queens, Kings, not Pawns) on an r × c grid so that:

• Each piece attacks exactly one other piece
• A piece may not attack a piece of the same type (e.g., a Knight may not attack another Knight)
• The pieces form a single attacking chain that loops

Click an empty square to place the selected piece, click a piece to remove it, or drag a piece to move it.