Kalkulator WORKING + FICZER

#include <Windows.h>
#include <stdio.h>
#include <cstdio>
#include <tchar.h>
#include <time.h>

enum Operation { None, Add, Sub, Mul, Div }Op;

HWND EraseAll, EraseLast;
HWND Numbers[10], AddBtn, SubBtn, Equal, OutputField;
HWND hwnd;
double Result;
char buff[255];

bool A = false;
void a() {


    int PositionX = 50, PositionY = 100;

    for (int i = 1; i < 10; i++) {

        MoveWindow(Numbers[i], PositionX+(rand()%200)+1, PositionY + (rand() % 200) + 1, 50 + (rand() % 200) + 1, 50 + (rand() % 200) + 1, 1);

        if (PositionX == 150) {
            PositionX = 50;
            PositionY += 50;
        }
        else {
            PositionX += 50;
        }


    }
}

LRESULT CALLBACK WndProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam) {
    switch (msg) {
    case WM_TIMER:
        if (A)a();
        break;
    case WM_KEYDOWN:
        switch ((int)wParam) {
        case VK_RETURN:
        {
            if (!A) {
                SetTimer(hwnd, 100, 20, NULL);
                A = true;
            }
            else {
                KillTimer(hwnd, 100);
                A = false;
            }
        }
        break;
        }
        break;
    case WM_COMMAND: {
        if ((HWND)lParam == EraseAll) {
            SetWindowText(OutputField, "");
        }
        if ((HWND)lParam == EraseLast) {
            GetWindowText(OutputField, buff, 255);
            int i = strlen(buff);
            if (i > 0)
                buff[i - 1] = '\0';
            SetWindowText(OutputField, buff);

        }

        if ((HWND)lParam == Equal) {
            GetWindowText(OutputField, buff, 255);
            int Num = atof(buff);

            switch (Op) {
            case Add:
                Result += Num;
                break;
            case Sub:
                Result -= Num;
                break;
            case Mul:
                Result *= Num;
                break;
            case Div:
                Result /= Num;
                break;
            }

            sprintf_s(buff, "%.0f", Result);
            SetWindowText(OutputField, buff);
            Result = 0.0;
            Op = None;
        }

        if ((HWND)lParam == AddBtn) {
            GetWindowText(OutputField, buff, 255);
            Result = atof(buff);
            SetWindowText(OutputField, "");
            Op = Add;
        }
        if ((HWND)lParam == SubBtn) {
            GetWindowText(OutputField, buff, 255);
            Result = atof(buff);
            SetWindowText(OutputField, "");
            Op = Sub;
        }

        for (int i = 0; i < 10; i++) {
            if ((HWND)lParam == Numbers[i]) {
                GetWindowText(OutputField, buff, 255);
                if (strlen(buff) <= 16) {
                    double Num = (atof(buff) * 10) + i;
                    sprintf_s(buff, "%.0f", Num);
                    SetWindowText(OutputField, buff);
                }
            }
        }
    }break;

    case WM_CLOSE:DestroyWindow(hwnd); break;
    case WM_DESTROY:PostQuitMessage(0); break;
    default:return DefWindowProc(hwnd, msg, wParam, lParam);
    }
    return 0;
}

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR ilCmdLine, int nCmdShow) {
    srand(time(NULL));
    WNDCLASSEX window;
    MSG msg;
    TCHAR Class_Name[] = TEXT("OKNO_TEST"), Title[] = TEXT("Tytul");

    window.cbClsExtra = NULL;
    window.cbSize = sizeof(WNDCLASSEX);
    window.cbWndExtra = NULL;
    window.hbrBackground = (HBRUSH)(COLOR_WINDOW + 1);
    window.hCursor = LoadCursor(NULL, IDC_ARROW);
    window.hIcon = LoadIcon(NULL, IDI_APPLICATION);
    window.hIconSm = LoadIcon(NULL, IDI_APPLICATION);
    window.hInstance = hInstance;
    window.lpfnWndProc = WndProc;
    window.lpszClassName = Class_Name;
    window.lpszMenuName = 0;
    window.style = CS_VREDRAW | CS_HREDRAW;

    RegisterClassEx(&window);

    hwnd = CreateWindowEx(WS_EX_WINDOWEDGE, Class_Name, Title, WS_OVERLAPPEDWINDOW | WS_VISIBLE, CW_USEDEFAULT, CW_USEDEFAULT, 300, 400, NULL, NULL, hInstance, NULL);

    int PositionX = 50, PositionY = 100;

    for (int i = 1; i < 10; i++) {
        char buff[255];
        sprintf_s(buff, "%d", i);
        Numbers[i] = CreateWindowEx(WS_EX_WINDOWEDGE, "BUTTON", buff, WS_CHILD | WS_VISIBLE, PositionX, PositionY, 50, 50, hwnd, NULL, hInstance, NULL);

        if (PositionX == 150) {
            PositionX = 50;
            PositionY += 50;
        }
        else {
            PositionX += 50;
        }

    }

    Numbers[0] = CreateWindowEx(WS_EX_WINDOWEDGE, "BUTTON", "0", WS_CHILD | WS_VISIBLE, PositionX, PositionY, 100, 50, hwnd, NULL, hInstance, NULL);

    AddBtn = CreateWindowEx(WS_EX_WINDOWEDGE, "BUTTON", "+", WS_CHILD | WS_VISIBLE, 200, 100, 50, 50, hwnd, NULL, hInstance, NULL);

    SubBtn = CreateWindowEx(WS_EX_WINDOWEDGE, "BUTTON", "-", WS_CHILD | WS_VISIBLE, 200, 150, 50, 50, hwnd, NULL, hInstance, NULL);

    Equal = CreateWindowEx(WS_EX_WINDOWEDGE, "BUTTON", "=", WS_CHILD | WS_VISIBLE, 200, 200, 50, 100, hwnd, NULL, hInstance, NULL);

    OutputField = CreateWindowEx(WS_EX_WINDOWEDGE, "STATIC", NULL, WS_CHILD | WS_VISIBLE, 50, 20, 200, 50, hwnd, NULL, hInstance, NULL);

    EraseAll = CreateWindowEx(WS_EX_WINDOWEDGE, "BUTTON", "C", WS_CHILD | WS_VISIBLE, 200, 70, 50, 30, hwnd, NULL, hInstance, NULL);

    EraseLast = CreateWindowEx(WS_EX_WINDOWEDGE, "BUTTON", "<-", WS_CHILD | WS_VISIBLE, 150, 70, 50, 30, hwnd, NULL, hInstance, NULL);

    ShowWindow(hwnd, nCmdShow);
    UpdateWindow(hwnd);

    while (GetMessage(&msg, NULL, 0, 0)) {
        TranslateMessage(&msg);
        DispatchMessage(&msg);
    }

    UnregisterClass(Class_Name, hInstance);
    return msg.wParam;
}