func (f *Field) PieceDroppable(piece *Piece, x, y int, angle Angle) bool {
	return !piece.collides(f, x, y+1, angle)
}
func (f *Field) PieceDroppable(piece *Piece, x, y int, angle Angle) bool {
	return !piece.collides(f, x, y+1, angle)
}
func ( f * Field ) PieceDroppable ( piece * Piece , x , y int , angle Angle ) bool { return ! piece . collides ( f , x , y + 1 , angle ) }
// PieceDroppable returns a boolean value indicating whether
// the piece at (x, y) with the given angle can drop.
PieceDroppable returns a boolean value indicating whether the piece at ( x y ) with the given angle can drop .