LG consists of a symmetric version of the pure residuation logic NL together with structure-preserving interaction principles relating the conjunctive and disjunctive operations.  We discuss these components in turn. For symmetry, the inventory of type-forming operations is doubled: in addition to the NL operations ⊗,\,/ (product, left and right division), there is a second family ⊕,⊘,⦸: coproduct, right and left difference.  The two families are related by an arrow reversal symmetry δ, which translates type formulas according to the table below.