func (f *Field) RotatePieceLeft(piece *Piece, x, y int, angle Angle) Angle {
	if piece.collides(f, x, y, angle.RotateLeft()) {
		return angle
	}
	return angle.RotateLeft()
}
func (f *Field) RotatePieceLeft(piece *Piece, x, y int, angle Angle) Angle {
	if piece.collides(f, x, y, angle.RotateLeft()) {
		return angle
	}
	return angle.RotateLeft()
}
func ( f * Field ) RotatePieceLeft ( piece * Piece , x , y int , angle Angle ) Angle { if piece . collides ( f , x , y , angle . RotateLeft ( ) ) { return angle } return angle . RotateLeft ( ) }
// RotatePieceLeft tries to rotate the piece to the left
// and returns the piece's next angle.
RotatePieceLeft tries to rotate the piece to the left and returns the piece s next angle .