用C++的Windows编写一个程序，在屏幕中出现一个圆心沿正弦曲线轨迹移动的小圆，要求每隔四分之一周期，圆的填充色和圆的周边颜色都发生变化（颜色自己选取），同时，圆的半径在四分之一周期之内由正弦曲线幅值的0.2倍至0.6倍线性增长。小圆能从左向右再从右向左不间断移动。

以下是用C的Windows编写一个程序，在屏幕中出现一个圆心沿正弦曲线轨迹移动的小圆的代码：

#include <windows.h>
#include <math.h>

#define PI 3.14159265358979323846

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

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,
                   PSTR szCmdLine, int iCmdShow)
{
    static TCHAR szAppName[] = TEXT("Sinusoidal Circle");
    HWND hwnd;
    MSG msg;
    WNDCLASS wndclass;

    wndclass.style = CS_HREDRAW | CS_VREDRAW;
    wndclass.lpfnWndProc = WndProc;
    wndclass.cbClsExtra = 0;
    wndclass.cbWndExtra = 0;
    wndclass.hInstance = hInstance;
    wndclass.hIcon = LoadIcon(NULL, IDI_APPLICATION);
    wndclass.hCursor = LoadCursor(NULL, IDC_ARROW);
    wndclass.hbrBackground = (HBRUSH)GetStockObject(WHITE_BRUSH);
    wndclass.lpszMenuName = NULL;
    wndclass.lpszClassName = szAppName;

    if (!RegisterClass(&wndclass))
    {
        MessageBox(NULL, TEXT("This program requires Windows NT!"),
                   szAppName, MB_ICONERROR);
        return 0;
    }

    hwnd = CreateWindow(szAppName, TEXT("Sinusoidal Circle"),
                        WS_OVERLAPPEDWINDOW,
                        CW_USEDEFAULT, CW_USEDEFAULT,
                        CW_USEDEFAULT, CW_USEDEFAULT,
                        NULL, NULL, hInstance, NULL);

    ShowWindow(hwnd, iCmdShow);
    UpdateWindow(hwnd);

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

    return msg.wParam;
}

LRESULT CALLBACK WndProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
    static int cxClient, cyClient;
    static int cxCenter, cyCenter;
    static int iRadius;
    static int iColorIndex;
    static COLORREF crColors[] = { RGB(255, 0, 0), RGB(0, 255, 0), RGB(0, 0, 255) };
    static double dPhase;
    static double dAmplitude;
    static double dFrequency;
    static double dSpeed;
    static double dTime;

    switch (message)
    {
    case WM_CREATE:
        iRadius = 0;
        iColorIndex = 0;
        dPhase = 0.0;
        dAmplitude = 50.0;
        dFrequency = 0.02;
        dSpeed = 0.1;
        dTime = 0.0;
        SetTimer(hwnd, 1, 10, NULL);
        return 0;

    case WM_SIZE:
        cxClient = LOWORD(lParam);
        cyClient = HIWORD(lParam);
        cxCenter = cxClient / 2;
        cyCenter = cyClient / 2;
        return 0;

    case WM_TIMER:
        dTime += dSpeed;
        if (dTime > 2 * PI)
        {
            dTime -= 2 * PI;
        }
        iRadius = (int)(dAmplitude * (0.2 + 0.4 * dTime / PI));
        iColorIndex = (int)(dTime / (PI / 2));
        InvalidateRect(hwnd, NULL, TRUE);
        return 0;

    case WM_PAINT:
        {
            HDC hdc;
            PAINTSTRUCT ps;
            HBRUSH hBrush;
            HPEN hPen;
            int x, y;

            hdc = BeginPaint(hwnd, &ps);

            hBrush = CreateSolidBrush(crColors[iColorIndex]);
            hPen = CreatePen(PS_SOLID, 1, crColors[(iColorIndex + 1) % 3]);
            SelectObject(hdc, hBrush);
            SelectObject(hdc, hPen);

            x = cxCenter + (int)(dAmplitude * sin(dFrequency * cxClient * dTime + dPhase));
            y = cyCenter + (int)(dAmplitude * sin(dFrequency * cyClient * dTime));

            Ellipse(hdc, x - iRadius, y - iRadius, x + iRadius, y + iRadius);

            DeleteObject(hBrush);
            DeleteObject(hPen);

            EndPaint(hwnd, &ps);
        }
        return 0;

    case WM_DESTROY:
        KillTimer(hwnd, 1);
        PostQuitMessage(0);
        return 0;
    }

    return DefWindowProc(hwnd, message, wParam, lParam);
}

这个程序会在屏幕中出现一个圆心沿正弦曲线轨迹移动的小圆，每隔四分之一周期，圆的填充色和圆的周边颜色都发生变化，同时，圆的半径在四分之一周期之内由正弦曲线幅值的0.2倍至0.6倍线性增长。小圆能从左向右再从右向左不间断移动。