GModeApp is an innovative application meticulously crafted to modernize and enhance the legacy code originally developed by A.I. Gavrishin, A. Coradini, M. Fulchignoni, and O. Fanucci. This transformation involved a comprehensive rewrite of the codebase utilizing object-oriented programming techniques, ensuring a more structured and efficient design. In addition, the code has been parallelized wherever feasible, significantly boosting performance and scalability. The user interface for inputting operational parameters has been streamlined, making it more intuitive and user-friendly.