A Windows-only Python script monitors battery percentage changes using ctypes to call Win32 APIs directly. Instead of polling, it creates a hidden message-only window to receive system notifications, providing real-time updates when power levels shift. This event-driven approach is efficient, running only when the OS signals a change.

The program subscribes to the battery percentage remaining power setting via a specific GUID. It handles `WM_POWERBROADCAST` messages, extracts data from the `POWERBROADCAST_SETTING` structure, and triggers a callback. This pattern is useful for background utilities, telemetry collectors, or any app needing immediate battery awareness without constant polling.

Clean shutdown is handled by registering a console control handler for Ctrl+C. This posts `WM_CLOSE` to the hidden window, triggering an orderly teardown of resources like the power notification and window class. The result is a small, reliable tool for integrating Python with low-level Windows event systems.