A web-based interactive simulation environment for the FeliX Integrated Assessment Model

<ns3:p>Background Integrated Assessment Models (IAMs) are essential tools for exploring the interconnections between climate, food, land use, biodiversity, and socioeconomic systems. However, their inherent complexity and dependence on proprietary modelling software have historically restricted their use to specialised research institutions. There is a critical need for accessible tools that mainstream complex IAM results through intuitive interfaces enabling policymakers, educators, and the general public to explore IAM-based scenarios without technical expertise or local software installations. Methods This study presents the design, implementation, and validation of a browser-based Interactive Simulation Environment (ISE) for the FeliX (Full of Economic-Environment Linkages and Integration dX/dt) Integrated Assessment Model. The Vensim system dynamics model is compiled to WebAssembly via an SDEverywhere transpilation toolchain, enabling real-time client-side execution. The architecture employs Web Workers for non-blocking computation, a configuration-driven interface using interoperable open-data formats to fully decouple the model from the UI layer, and interactive visualisations built with Chart.js. A three-level validation framework verified numerical fidelity across the transpilation pipeline, and transferability was assessed through a proof-of-concept SIR epidemiological model deployment. Results The transpiled WebAssembly model reproduces original Vensim outputs to floating-point precision across all nine thematic output domains (food systems, nutrition, land use, greenhouse gas emissions, fertiliser use, biodiversity, and water resources). The configuration-driven architecture enables deployment with alternative Vensim models without code modifications. The platform supports multi-scenario comparison, scenario import/export, progressive disclosure interfaces, and contextual documentation, all running client-side in standard web browsers. Conclusions The FeliX ISE demonstrates the feasibility of compiling complex system dynamics IAMs to WebAssembly for fully browser-based interactive scenario exploration. The modular, configuration-driven architecture ensures transferability to other Vensim-based models. The interface design lowers the expertise threshold for meaningful engagement with integrated assessment science, broadening participation in climate and food system policy analysis.</ns3:p>