*TUT* C/C++ Screen Melting Effect / Prank

Code
#include <Windows.h>



int ScreenWidth, ScreenHeight;

int Interval = 100;



// callback for the melting effect

LRESULT CALLBACK Melter(HWND hWnd, UINT Msg, WPARAM wParam, LPARAM lParam)

{

    switch (Msg)

    {

    case WM_CREATE:

    {

        HDC Desktop = GetDC(HWND_DESKTOP);

        HDC Window = GetDC(hWnd);



        BitBlt(Window, 0, 0, ScreenWidth, ScreenHeight, Desktop, 0, 0, SRCCOPY);

        ReleaseDC(hWnd, Window);

        ReleaseDC(HWND_DESKTOP, Desktop);



        SetTimer(hWnd, 0, Interval, 0);

        ShowWindow(hWnd, SW_SHOW);

        break;

    }

    case WM_PAINT:

    {

        ValidateRect(hWnd, 0);

        break;

    }

    case WM_TIMER:

    {

        HDC Window = GetDC(hWnd);

        int X = (rand() % ScreenWidth) - (150 / 2),

            Y = (rand() % 15),

            Width = (rand() % 150);

        BitBlt(Window, X, Y, Width, ScreenHeight, Window, X, 0, SRCCOPY);

        ReleaseDC(hWnd, Window);

        break;

    }

    case WM_DESTROY:

    {

        KillTimer(hWnd, 0);

        PostQuitMessage(0);

        break;

    }

    return 0;

    }

    return DefWindowProc(hWnd, Msg, wParam, lParam);

}



int APIENTRY WinMain(HINSTANCE Inst, HINSTANCE Prev, LPSTR Cmd, int showcmd)

{

    // Get the width & height of current display

    ScreenWidth = GetSystemMetrics(SM_CXSCREEN);

    ScreenHeight = GetSystemMetrics(SM_CYSCREEN);

// class for initializing the window

    WNDCLASS wndClass = { 0, Melter, 0,0, Inst, 0, LoadCursorW(0,IDC_ARROW), 0, 0, L"ScreenMelter" };

    

// register the class

    if (RegisterClass(&wndClass))

    {

        // Create the "melter", an overlapping window.

        HWND hWnd = CreateWindowExA(WS_EX_TOPMOST, "ScreenMelter", 0, WS_POPUP,

            0, 0, ScreenWidth, ScreenHeight, HWND_DESKTOP, 0, Inst, 0);



        if (hWnd) //if the window is created successfully

        {

            // seed for randomization

            srand(GetTickCount());

            MSG Msg = { 0 };

            // Run the melter loop as long as the program isn't given the shutdown signal

            while (Msg.message != WM_QUIT)

            {

                if (PeekMessage(&Msg, 0, 0, 0, PM_REMOVE))

                {

                    TranslateMessage(&Msg);

                    DispatchMessage(&Msg);

                }

            }

        }

    }

    return 0;

}