C++ GDI Screen Darkener

darkr.cpp

#include <windows.h>

int main() {
    HDC hdc;
    int w = GetSystemMetrics(0);
    int h = GetSystemMetrics(1);
    while (1) {
        hdc = GetDC(0);
        BitBlt(hdc, rand() % 2, rand() % 2, w, h, hdc, rand() % 2, rand() % 2, SRCAND);
        Sleep(10);
    }
}