#include <windows.h>

#define NUM 32767

LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,
    PSTR szCmdLine, int iCmdShow)
{
    static int iKeep[NUM][4];
    HDC        hdcScr, hdcMem;
    int        cx, cy;
    HBITMAP    hBitmap;
    HWND       hwnd;
    int        i, j, x1, y1, x2, y2;

    if (LockWindowUpdate(hwnd = GetDesktopWindow()))
    {
        hdcScr = GetDCEx(hwnd, NULL, DCX_CACHE | DCX_LOCKWINDOWUPDATE);
        hdcMem = CreateCompatibleDC(hdcScr);
        cx = GetSystemMetrics(SM_CXSCREEN) / 10;
        cy = GetSystemMetrics(SM_CYSCREEN) / 10;
        hBitmap = CreateCompatibleBitmap(hdcScr, cx, cy);

        SelectObject(hdcMem, hBitmap);

        srand((int)GetCurrentTime());

        for (i = 0; i < 2; i++)
        for (j = 0; j < NUM; j++)
        {
            LockWindowUpdate(hwnd = GetDesktopWindow());
            if (i == 0)
            {
                iKeep[j][0] = x1 = cx * (rand() % 10);
                iKeep[j][1] = y1 = cy * (rand() % 10);
                iKeep[j][2] = x2 = cx * (rand() % 10);
                iKeep[j][3] = y2 = cy * (rand() % 10);
            }
            else
            {
                x1 = iKeep[NUM - 1 - j][0];
                y1 = iKeep[NUM - 1 - j][1];
                x2 = iKeep[NUM - 1 - j][2];
                y2 = iKeep[NUM - 1 - j][3];
            }
            BitBlt(hdcMem, 0, 0, cx, cy, hdcScr, x1, y1, SRCCOPY);
            BitBlt(hdcScr, x1, y1, cx, cy, hdcScr, x2, y2, SRCCOPY);
            BitBlt(hdcScr, x2, y2, cx, cy, hdcMem, 0, 0, SRCCOPY);
        }

        DeleteDC(hdcMem);
        ReleaseDC(hwnd, hdcScr);
        DeleteObject(hBitmap);
    }
    return 0;
}