High-level synthesis or “hardware compilation” is a behavioural synthesis method in which circuits are specified using conventional programming languages. Such languages are generally recognised as more accessible than hardware description languages, and it is expected that their use would significantly increase design productivity. The Geometry of Synthesis is a new hardware compilation technique which achieves this goal in a semantic-directed fashion, by noting that functional programming languages and diagrammatic descriptions of hardware share a common mathematical structure, and by using the game-semantic model of the programming language to reduce all computational effects to signal-like message passing. As a consequence, this technique has mature support for higher-order functions , local (assignable) state , concurrency  and (affine) recursion . Moreover, the compiler can support features such as separate compilation, libraries and a foreign-function interface . The programming language of GoS, Verity, is an “Algol-like” language  extended with concurrency features . The interplay between the call-by-name function mechanism and local effects, an approach specific to Algol, is the key ingredient which makes it possible for a large class of programs in this language to have finitely representable semantic models which can be synthesised as stand-alone static circuits. The compiler is available as an open-source download.