In all software development projects, engineers face the challenge of translating the requirements layer into a design layer, then into an implementation-code layer, and then validating the correctness of the result. Many methodologies, languages and tools exist for facilitating the process, including multiple back-and-forth `refinement trips' across the requirements, design and implementation layers, by focusing on formalizing the artifacts involved and on automating a variety of tasks throughout. In this paper, we introduce a novel and unique development environment, which integrates scenario-based programming (SBP) via the LSC language and the object-oriented, visual Statecharts formalism, for the development of reactive systems. LSC targets creation of models and systems directly from requirement specifications, and Statecharts is used mainly for specifying final component behavior. Our integration enables semantically-rich joint execution, with the sharing and interfacing of objects and events, and can be used for creating and then gradually enhancing testable models from early in requirements elicitation through detailed design. In some cases, it can be used for generating final system code. We describe the technical details of the integration and its semantics and discuss its significance for future development methodologies.