Operational game semantics (OGS) is a method for interpreting programs as strategies in suitable games, or more precisely as labelled transition systems over suitable games, in the sense of Levy and Staton. Such an interpretation is called sound when, for any two given programs, bisimilarity of associated strategies entails contextual equivalence. OGS has been applied to a variety of languages, with rather tedious soundness proofs. In this paper, we contribute to the unification and mechanisation of OGS. Indeed, we propose an abstract notion of language with evaluator, for which we construct a generic OGS interpretation, which we prove sound. Our framework covers a variety of simply-typed and untyped lambda-calculi, notably featuring fixed points, continuations, and recursive datatypes. All constructions and proofs are entirely mechanised in the Coq proof assistant.