Worked on enhancing power efficiency in GPU synchronization for the libsdl-org/SDL repository, specifically targeting Metal fence synchronization on macOS. Addressed the issue of CPU-intensive busy-wait loops by implementing native Metal completion handlers and dispatch semaphores, allowing the CPU to remain idle while waiting for GPU tasks to complete. This approach reduced unnecessary CPU wakeups and improved battery life, while maintaining accurate tracking of command buffer status through completion callbacks instead of polling. The work was implemented using C, Metal, and Objective-C, resulting in a focused and maintainable change with clear performance benefits for macOS users of SDL.