Piece representation

Chess.sol

contract Chess {
  /// ======================================Piece Representation======================================
  /// Each chess piece is defined with 4 bits as follows:
  ///     * The first bit denotes the color (0 means black; 1 means white).
  ///     * The last 3 bits denote the type:
  ///         | Bits | # | Type   |
  ///         | ---- | - | ------ |
  ///         | 000  | 0 | Empty  |
  ///         | 001  | 1 | Pawn   |
  ///         | 010  | 2 | Bishop |
  ///         | 011  | 3 | Rook   |
  ///         | 100  | 4 | Knight |
  ///         | 101  | 5 | Queen  |
  ///         | 110  | 6 | King   |
}