A -x developer is responsible for creating and maintaining interactive, high-performance games and applications. This involves utilizing the -x framework to develop cross-platform apps, mainly for mobile devices. They write clean, efficient codes in C++, ensuring seamless gameplay and optimal user experience. They also debug and troubleshoot any issues, optimize the performance of applications, and integrate various APIs and services. They collaborate with designers and other developers to implement game logic and visual elements, and ensure the proper functionality of the application across different platforms. Furthermore, they may also be involved in updating and improving existing applications.