LongBow & Arrow Wireframe Animation (Claude 3.7 (O3 AI Initial))

I want to draw the 'fletching' for the bottom side of the arrow as well (should be fletching on top and bottom), mirroring the top, and also make the fletching swept backward instead of front as it is presently (make it point the correct side).

Here's the modified code for the fletching section in diff-like format:

```diff
// Fletching (3 short diagonal lines)
const float fletch = 20.0f;
const float step = 5.0f;
// Top fletching
for (int i = 0; i < 3; ++i)
{
    float x = g_arrowPosX - arrowLen + i * step;
    g_pRenderTarget->DrawLine(
        D2D1::Point2F(x, arrowY),
-       D2D1::Point2F(x + fletch, arrowY - fletch * 0.4f + i * 3.0f),
+       D2D1::Point2F(x - fletch, arrowY - fletch * 0.4f + i * 3.0f),
        g_pBrush, 2.0f);
}
+ // Bottom fletching
+ for (int i = 0; i < 3; ++i)
+ {
+     float x = g_arrowPosX - arrowLen + i * step;
+     g_pRenderTarget->DrawLine(
+         D2D1::Point2F(x, arrowY),
+         D2D1::Point2F(x - fletch, arrowY + fletch * 0.4f - i * 3.0f),
+         g_pBrush, 2.0f);
+ }
```

Would you like me to explain the changes I made to the code?

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New Code /w Fixes:::
//  BowAndArrow.cpp
//  Simple Win32 / Direct2D demo - "wireframe longbow"
//  Build: cl /EHsc /DUNICODE /D_UNICODE BowAndArrow.cpp d2d1.lib user32.lib gdi32.lib

#include <windows.h>
#include <d2d1.h>
#include <chrono>
#include <cmath>
#include <algorithm>
#pragma comment(lib, "d2d1")

// -------------------------------------------------
// Small RAII helper to release COM objects
// -------------------------------------------------
template<class T> void SafeRelease(T** pp)
{
    if (*pp) { (*pp)->Release(); *pp = nullptr; }
}

// -------------------------------------------------
// Animation constants
// -------------------------------------------------
constexpr float  COCK_TIME = 1.0f;   // seconds
constexpr float  HOLD_TIME = 0.5f;   // seconds
constexpr float  FIRE_TIME = 1.0f;   // seconds
constexpr UINT   TIMER_ID = 1;
constexpr UINT   TIMER_MS = 16;     // ~60 FPS

enum class AnimStage { Cocking, Hold, Firing, Done };
constexpr float ARROW_REST_OFFSET = 500.0f;   // pixels in-front of bow ( > 0 )

// String pull distance (pixels) and bow X center
constexpr float STRING_MAX_PULL = 180.0f;
constexpr float CX_BOW = 220.0f;

// -------------------------------------------------
// Global state (kept simple for a demo)
// -------------------------------------------------
HWND                    g_hWnd = nullptr;
ID2D1Factory* g_pFactory = nullptr;
ID2D1HwndRenderTarget* g_pRenderTarget = nullptr;
ID2D1SolidColorBrush* g_pBrush = nullptr;

float g_windowW = 1280.0f;
float g_windowH = 720.0f;
float g_arrowPosX = CX_BOW + ARROW_REST_OFFSET;   // head starts free-floating

// Geometry helpers (depend on window height, so they are updated in WM_SIZE)
float cx = CX_BOW;
float topY = 120.0f;
float bottomY = 600.0f;   // will be overwritten in WM_SIZE
float midY = 360.0f;
float halfHeight = 240.0f;

// Animation variables
AnimStage   g_stage = AnimStage::Cocking;
float       g_timeInStage = 0.0f;        // seconds
auto        g_prevTick = std::chrono::high_resolution_clock::now();
float       g_stringOffset = 0.0f;        // 0 = relaxed, 1 = fully drawn
//float       g_arrowPosX = 0.0f;        // head position

// -------------------------------------------------
// Helpers
// -------------------------------------------------
float Lerp(float a, float b, float t) { return a + (b - a) * t; }

// Create or re-create render target
HRESULT CreateDeviceResources()
{
    if (g_pRenderTarget) return S_OK;

    RECT rc; GetClientRect(g_hWnd, &rc);

    D2D1_SIZE_U size = D2D1::SizeU(rc.right - rc.left,
        rc.bottom - rc.top);

    HRESULT hr = g_pFactory->CreateHwndRenderTarget(
        D2D1::RenderTargetProperties(),
        D2D1::HwndRenderTargetProperties(g_hWnd, size),
        &g_pRenderTarget);

    if (SUCCEEDED(hr))
        hr = g_pRenderTarget->CreateSolidColorBrush(
            D2D1::ColorF(D2D1::ColorF::White), &g_pBrush);

    return hr;
}

void DiscardDeviceResources()
{
    SafeRelease(&g_pBrush);
    SafeRelease(&g_pRenderTarget);
}

// -------------------------------------------------
// Core rendering
// -------------------------------------------------
void OnRender()
{
    if (FAILED(CreateDeviceResources()))
        return;

    g_pRenderTarget->BeginDraw();
    g_pRenderTarget->Clear(D2D1::ColorF(0x202020)); // dark bg

    // -------------------------------------------------
    // 1. Draw Bow limbs (two quadratic curves)
    // -------------------------------------------------
    ID2D1PathGeometry* pGeom = nullptr;
    ID2D1GeometrySink* pSink = nullptr;
    if (SUCCEEDED(g_pFactory->CreatePathGeometry(&pGeom)))
    {
        pGeom->Open(&pSink);

        //--------------------------------------------------------------
        //  One continuous ")"-shaped limb with a slightly pointy tip.
        //  End-points stay on the string ( (cx, topY) & (cx, bottomY) )
        //--------------------------------------------------------------
        constexpr float NOSE = 35.0f;               // how far the tips stick out
        const     float BULGE = halfHeight * 0.5f;  // max belly distance (x)

        pSink->BeginFigure(D2D1::Point2F(cx, topY), D2D1_FIGURE_BEGIN_HOLLOW);

        // Draw semicircle bow with pointy tip at middle
        // First quarter - top to middle-top
        pSink->AddBezier(
            D2D1::BezierSegment(
                D2D1::Point2F(cx + NOSE, topY + halfHeight * 0.1f),      // slight curve at top
                D2D1::Point2F(cx + BULGE, topY + halfHeight * 0.5f),     // first quarter curve
                D2D1::Point2F(cx + BULGE + NOSE, midY - NOSE)));         // approaching tip

        // Middle part with pointy tip
        pSink->AddBezier(
            D2D1::BezierSegment(
                D2D1::Point2F(cx + BULGE + NOSE * 1.2f, midY - NOSE * 0.5f),  // curve to tip
                D2D1::Point2F(cx + BULGE + NOSE * 1.5f, midY),               // pointy tip
                D2D1::Point2F(cx + BULGE + NOSE * 1.2f, midY + NOSE * 0.5f)));  // curve from tip

        // Last quarter - middle-bottom to bottom
        pSink->AddBezier(
            D2D1::BezierSegment(
                D2D1::Point2F(cx + BULGE + NOSE, midY + NOSE),            // after tip
                D2D1::Point2F(cx + BULGE, bottomY - halfHeight * 0.5f),   // last quarter curve
                D2D1::Point2F(cx + NOSE, bottomY - halfHeight * 0.1f)));  // approaching bottom

        // Connect back to string
        pSink->AddBezier(
            D2D1::BezierSegment(
                D2D1::Point2F(cx + NOSE * 0.5f, bottomY - NOSE * 0.25f),  // curve to bottom
                D2D1::Point2F(cx, bottomY),                              // bottom endpoint
                D2D1::Point2F(cx, bottomY)));                            // dummy point (required)

        pSink->EndFigure(D2D1_FIGURE_END_OPEN);

        pSink->Close();
        g_pRenderTarget->DrawGeometry(pGeom, g_pBrush, 2.0f);

        SafeRelease(&pSink);
        SafeRelease(&pGeom);
    }

    // -------------------------------------------------
    // 2. Draw Bow string
    // -------------------------------------------------
    float pull = g_stringOffset * STRING_MAX_PULL;
    D2D1_POINT_2F p1 = D2D1::Point2F(cx, topY);
    D2D1_POINT_2F pm = D2D1::Point2F(cx - pull, midY);
    D2D1_POINT_2F p2 = D2D1::Point2F(cx, bottomY);

    g_pRenderTarget->DrawLine(p1, pm, g_pBrush, 2.0f);
    g_pRenderTarget->DrawLine(pm, p2, g_pBrush, 2.0f);

    // -------------------------------------------------
    // 3. Draw Arrow (simple shaft + head + tail)
    // -------------------------------------------------
    float arrowY = midY;
    float arrowLen = 240.0f;
    float arrowHead = 18.0f;

    // Shaft
    g_pRenderTarget->DrawLine(
        D2D1::Point2F(g_arrowPosX, arrowY),
        D2D1::Point2F(g_arrowPosX - arrowLen, arrowY),
        g_pBrush, 2.0f);

    // Arrow head (small triangle)
    D2D1_POINT_2F headPts[3] = {
        D2D1::Point2F(g_arrowPosX,                 arrowY),
        D2D1::Point2F(g_arrowPosX - arrowHead,     arrowY - arrowHead * 0.5f),
        D2D1::Point2F(g_arrowPosX - arrowHead,     arrowY + arrowHead * 0.5f)
    };
    g_pRenderTarget->DrawLine(headPts[0], headPts[1], g_pBrush, 2.0f);
    g_pRenderTarget->DrawLine(headPts[0], headPts[2], g_pBrush, 2.0f);

    // Fletching (3 short diagonal lines)
    const float fletch = 20.0f;
    const float step = 5.0f;
    // Top fletching
    for (int i = 0; i < 6; ++i)
    {
        float x = g_arrowPosX - arrowLen + i * step;
        g_pRenderTarget->DrawLine(
            D2D1::Point2F(x, arrowY),
            D2D1::Point2F(x - fletch, arrowY - fletch * 0.4f + i * 3.0f),
            g_pBrush, 2.0f);
    }
    // Bottom fletching
    for (int i = 0; i < 6; ++i)
    {
        float x = g_arrowPosX - arrowLen + i * step;
        g_pRenderTarget->DrawLine(
            D2D1::Point2F(x, arrowY),
            D2D1::Point2F(x - fletch, arrowY + fletch * 0.4f - i * 3.0f),
            g_pBrush, 2.0f);
    }

    // Present
    HRESULT hr = g_pRenderTarget->EndDraw();
    if (hr == D2DERR_RECREATE_TARGET)
        DiscardDeviceResources();
}

// -------------------------------------------------
// Animation tick (called from WM_TIMER)
// -------------------------------------------------
void UpdateAnimation()
{
    // Compute delta time
    auto  now = std::chrono::high_resolution_clock::now();
    float dt = std::chrono::duration<float>(now - g_prevTick).count();
    g_prevTick = now;
    g_timeInStage += dt;

    switch (g_stage)
    {
    case AnimStage::Cocking:
    {
        float t = min(g_timeInStage / COCK_TIME, 1.0f);
        g_stringOffset = t;                       // 0 -> 1  (string pulled left)

        float startX = cx + ARROW_REST_OFFSET;          // <<< NEW
        float cockedX = cx - STRING_MAX_PULL + 50.0f;    // same as before
        g_arrowPosX = Lerp(startX, cockedX, t);

        if (t >= 1.0f) { g_stage = AnimStage::Hold; g_timeInStage = 0.f; }
    } break;

    case AnimStage::Hold:
        if (g_timeInStage >= HOLD_TIME)
        {
            g_stage = AnimStage::Firing; g_timeInStage = 0.f;
        }
        break;

    case AnimStage::Firing:
    {
        float t = min(g_timeInStage / FIRE_TIME, 1.0f);
        g_stringOffset = 1.0f - t;             // 1 -> 0  (same)

        float startX = cx - STRING_MAX_PULL + 50.0f;  // << same value as cockedX
        float endX = g_windowW + 100.0f;            // fly off screen right
        g_arrowPosX = Lerp(startX, endX, t);

        if (t >= 1.0f)
        {
            g_stage = AnimStage::Cocking; g_timeInStage = 0.f;
        } // loop
    } break;

    case AnimStage::Done:
        // Not used anymore, but kept for completeness
        break;
    }

    // Request redraw
    InvalidateRect(g_hWnd, nullptr, FALSE);
}

// -------------------------------------------------
// Window procedure
// -------------------------------------------------
LRESULT CALLBACK WndProc(HWND hWnd, UINT msg,
    WPARAM wParam, LPARAM lParam)
{
    switch (msg)
    {
    case WM_CREATE:
        if (FAILED(D2D1CreateFactory(D2D1_FACTORY_TYPE_SINGLE_THREADED,
            &g_pFactory)))
            return -1; // abort window creation
        SetTimer(hWnd, TIMER_ID, TIMER_MS, nullptr);
        g_prevTick = std::chrono::high_resolution_clock::now();
        return 0;

    case WM_SIZE:
    {
        g_windowW = static_cast<float>(LOWORD(lParam));
        g_windowH = static_cast<float>(HIWORD(lParam));

        // Update dependent geometry values
        topY = 120.0f;
        bottomY = g_windowH - 120.0f;
        midY = (topY + bottomY) * 0.5f;
        halfHeight = (bottomY - topY) * 0.5f;

        if (g_pRenderTarget)
            g_pRenderTarget->Resize(
                D2D1::SizeU(static_cast<UINT>(g_windowW),
                    static_cast<UINT>(g_windowH)));
    }
    return 0;

    case WM_TIMER:
        if (wParam == TIMER_ID)
            UpdateAnimation();
        return 0;

    case WM_PAINT:
    {
        PAINTSTRUCT ps;
        BeginPaint(hWnd, &ps);
        OnRender();
        EndPaint(hWnd, &ps);
    } return 0;

    case WM_DESTROY:
        KillTimer(hWnd, TIMER_ID);
        DiscardDeviceResources();
        SafeRelease(&g_pFactory);
        PostQuitMessage(0);
        return 0;
    }
    return DefWindowProc(hWnd, msg, wParam, lParam);
}

// -------------------------------------------------
// WinMain - entry point
// -------------------------------------------------
int WINAPI wWinMain(HINSTANCE hInst, HINSTANCE, PWSTR, int nCmdShow)
{
    const wchar_t CLASS_NAME[] = L"BowWindow";

    WNDCLASS wc = {};
    wc.lpfnWndProc = WndProc;
    wc.hInstance = hInst;
    wc.hCursor = LoadCursor(nullptr, IDC_ARROW);
    wc.lpszClassName = CLASS_NAME;
    RegisterClass(&wc);

    g_hWnd = CreateWindowEx(0, CLASS_NAME, L"Direct2D - Longbow Demo",
        WS_OVERLAPPEDWINDOW,
        CW_USEDEFAULT, CW_USEDEFAULT,
        static_cast<int>(g_windowW),
        static_cast<int>(g_windowH),
        nullptr, nullptr, hInst, nullptr);

    ShowWindow(g_hWnd, nCmdShow);

    // Main message loop
    MSG msg;
    while (GetMessage(&msg, nullptr, 0, 0))
    {
        TranslateMessage(&msg);
        DispatchMessage(&msg);
    }
    return 0;
}

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Original Code:::
//  BowAndArrow.cpp
//  Simple Win32 / Direct2D demo - "wireframe longbow"
//  Build: cl /EHsc /DUNICODE /D_UNICODE BowAndArrow.cpp d2d1.lib user32.lib gdi32.lib

#include <windows.h>
#include <d2d1.h>
#include <chrono>
#include <cmath>
#include <algorithm>
#pragma comment(lib, "d2d1")

// -------------------------------------------------
// Small RAII helper to release COM objects
// -------------------------------------------------
template<class T> void SafeRelease(T** pp)
{
    if (*pp) { (*pp)->Release(); *pp = nullptr; }
}

// -------------------------------------------------
// Animation constants
// -------------------------------------------------
constexpr float  COCK_TIME = 1.0f;   // seconds
constexpr float  HOLD_TIME = 0.5f;   // seconds
constexpr float  FIRE_TIME = 1.0f;   // seconds
constexpr UINT   TIMER_ID = 1;
constexpr UINT   TIMER_MS = 16;     // ~60 FPS

enum class AnimStage { Cocking, Hold, Firing, Done };
constexpr float ARROW_REST_OFFSET = 500.0f;   // pixels in-front of bow ( > 0 )

// String pull distance (pixels) and bow X center
constexpr float STRING_MAX_PULL = 180.0f;
constexpr float CX_BOW = 220.0f;

// -------------------------------------------------
// Global state (kept simple for a demo)
// -------------------------------------------------
HWND                    g_hWnd = nullptr;
ID2D1Factory* g_pFactory = nullptr;
ID2D1HwndRenderTarget* g_pRenderTarget = nullptr;
ID2D1SolidColorBrush* g_pBrush = nullptr;

float g_windowW = 1280.0f;
float g_windowH = 720.0f;
float g_arrowPosX = CX_BOW + ARROW_REST_OFFSET;   // head starts free-floating

// Geometry helpers (depend on window height, so they are updated in WM_SIZE)
float cx = CX_BOW;
float topY = 120.0f;
float bottomY = 600.0f;   // will be overwritten in WM_SIZE
float midY = 360.0f;
float halfHeight = 240.0f;

// Animation variables
AnimStage   g_stage = AnimStage::Cocking;
float       g_timeInStage = 0.0f;        // seconds
auto        g_prevTick = std::chrono::high_resolution_clock::now();
float       g_stringOffset = 0.0f;        // 0 = relaxed, 1 = fully drawn
//float       g_arrowPosX = 0.0f;        // head position

// -------------------------------------------------
// Helpers
// -------------------------------------------------
float Lerp(float a, float b, float t) { return a + (b - a) * t; }

// Create or re-create render target
HRESULT CreateDeviceResources()
{
    if (g_pRenderTarget) return S_OK;

    RECT rc; GetClientRect(g_hWnd, &rc);

    D2D1_SIZE_U size = D2D1::SizeU(rc.right - rc.left,
        rc.bottom - rc.top);

    HRESULT hr = g_pFactory->CreateHwndRenderTarget(
        D2D1::RenderTargetProperties(),
        D2D1::HwndRenderTargetProperties(g_hWnd, size),
        &g_pRenderTarget);

    if (SUCCEEDED(hr))
        hr = g_pRenderTarget->CreateSolidColorBrush(
            D2D1::ColorF(D2D1::ColorF::White), &g_pBrush);

    return hr;
}

void DiscardDeviceResources()
{
    SafeRelease(&g_pBrush);
    SafeRelease(&g_pRenderTarget);
}

// -------------------------------------------------
// Core rendering
// -------------------------------------------------
void OnRender()
{
    if (FAILED(CreateDeviceResources()))
        return;

    g_pRenderTarget->BeginDraw();
    g_pRenderTarget->Clear(D2D1::ColorF(0x202020)); // dark bg

    // -------------------------------------------------
    // 1. Draw Bow limbs (two quadratic curves)
    // -------------------------------------------------
    ID2D1PathGeometry* pGeom = nullptr;
    ID2D1GeometrySink* pSink = nullptr;
    if (SUCCEEDED(g_pFactory->CreatePathGeometry(&pGeom)))
    {
        pGeom->Open(&pSink);

        //--------------------------------------------------------------
        //  One continuous ")"-shaped limb with a slightly pointy tip.
        //  End-points stay on the string ( (cx, topY) & (cx, bottomY) )
        //--------------------------------------------------------------
        constexpr float NOSE = 35.0f;               // how far the tips stick out
        const     float BULGE = halfHeight * 0.5f;  // max belly distance (x)

        pSink->BeginFigure(D2D1::Point2F(cx, topY), D2D1_FIGURE_BEGIN_HOLLOW);

        // Draw semicircle bow with pointy tip at middle
        // First quarter - top to middle-top
        pSink->AddBezier(
            D2D1::BezierSegment(
                D2D1::Point2F(cx + NOSE, topY + halfHeight * 0.1f),      // slight curve at top
                D2D1::Point2F(cx + BULGE, topY + halfHeight * 0.5f),     // first quarter curve
                D2D1::Point2F(cx + BULGE + NOSE, midY - NOSE)));         // approaching tip

        // Middle part with pointy tip
        pSink->AddBezier(
            D2D1::BezierSegment(
                D2D1::Point2F(cx + BULGE + NOSE * 1.2f, midY - NOSE * 0.5f),  // curve to tip
                D2D1::Point2F(cx + BULGE + NOSE * 1.5f, midY),               // pointy tip
                D2D1::Point2F(cx + BULGE + NOSE * 1.2f, midY + NOSE * 0.5f)));  // curve from tip

        // Last quarter - middle-bottom to bottom
        pSink->AddBezier(
            D2D1::BezierSegment(
                D2D1::Point2F(cx + BULGE + NOSE, midY + NOSE),            // after tip
                D2D1::Point2F(cx + BULGE, bottomY - halfHeight * 0.5f),   // last quarter curve
                D2D1::Point2F(cx + NOSE, bottomY - halfHeight * 0.1f)));  // approaching bottom

        // Connect back to string
        pSink->AddBezier(
            D2D1::BezierSegment(
                D2D1::Point2F(cx + NOSE * 0.5f, bottomY - NOSE * 0.25f),  // curve to bottom
                D2D1::Point2F(cx, bottomY),                              // bottom endpoint
                D2D1::Point2F(cx, bottomY)));                            // dummy point (required)

        pSink->EndFigure(D2D1_FIGURE_END_OPEN);

        pSink->Close();
        g_pRenderTarget->DrawGeometry(pGeom, g_pBrush, 2.0f);

        SafeRelease(&pSink);
        SafeRelease(&pGeom);
    }

    // -------------------------------------------------
    // 2. Draw Bow string
    // -------------------------------------------------
    float pull = g_stringOffset * STRING_MAX_PULL;
    D2D1_POINT_2F p1 = D2D1::Point2F(cx, topY);
    D2D1_POINT_2F pm = D2D1::Point2F(cx - pull, midY);
    D2D1_POINT_2F p2 = D2D1::Point2F(cx, bottomY);

    g_pRenderTarget->DrawLine(p1, pm, g_pBrush, 2.0f);
    g_pRenderTarget->DrawLine(pm, p2, g_pBrush, 2.0f);

    // -------------------------------------------------
    // 3. Draw Arrow (simple shaft + head + tail)
    // -------------------------------------------------
    float arrowY = midY;
    float arrowLen = 240.0f;
    float arrowHead = 18.0f;

    // Shaft
    g_pRenderTarget->DrawLine(
        D2D1::Point2F(g_arrowPosX, arrowY),
        D2D1::Point2F(g_arrowPosX - arrowLen, arrowY),
        g_pBrush, 2.0f);

    // Arrow head (small triangle)
    D2D1_POINT_2F headPts[3] = {
        D2D1::Point2F(g_arrowPosX,                 arrowY),
        D2D1::Point2F(g_arrowPosX - arrowHead,     arrowY - arrowHead * 0.5f),
        D2D1::Point2F(g_arrowPosX - arrowHead,     arrowY + arrowHead * 0.5f)
    };
    g_pRenderTarget->DrawLine(headPts[0], headPts[1], g_pBrush, 2.0f);
    g_pRenderTarget->DrawLine(headPts[0], headPts[2], g_pBrush, 2.0f);

    // Fletching (3 short diagonal lines)
    const float fletch = 20.0f;
    const float step = 5.0f;
    for (int i = 0; i < 3; ++i)
    {
        float x = g_arrowPosX - arrowLen + i * step;
        g_pRenderTarget->DrawLine(
            D2D1::Point2F(x, arrowY),
            D2D1::Point2F(x + fletch, arrowY - fletch * 0.4f + i * 3.0f),
            g_pBrush, 2.0f);
    }

    // Present
    HRESULT hr = g_pRenderTarget->EndDraw();
    if (hr == D2DERR_RECREATE_TARGET)
        DiscardDeviceResources();
}

// -------------------------------------------------
// Animation tick (called from WM_TIMER)
// -------------------------------------------------
void UpdateAnimation()
{
    // Compute delta time
    auto  now = std::chrono::high_resolution_clock::now();
    float dt = std::chrono::duration<float>(now - g_prevTick).count();
    g_prevTick = now;
    g_timeInStage += dt;

    switch (g_stage)
    {
    case AnimStage::Cocking:
    {
        float t = min(g_timeInStage / COCK_TIME, 1.0f);
        g_stringOffset = t;                       // 0 -> 1  (string pulled left)

        float startX = cx + ARROW_REST_OFFSET;          // <<< NEW
        float cockedX = cx - STRING_MAX_PULL + 50.0f;    // same as before
        g_arrowPosX = Lerp(startX, cockedX, t);

        if (t >= 1.0f) { g_stage = AnimStage::Hold; g_timeInStage = 0.f; }
    } break;

    case AnimStage::Hold:
        if (g_timeInStage >= HOLD_TIME)
        {
            g_stage = AnimStage::Firing; g_timeInStage = 0.f;
        }
        break;

    case AnimStage::Firing:
    {
        float t = min(g_timeInStage / FIRE_TIME, 1.0f);
        g_stringOffset = 1.0f - t;             // 1 -> 0  (same)

        float startX = cx - STRING_MAX_PULL + 50.0f;  // << same value as cockedX
        float endX = g_windowW + 100.0f;            // fly off screen right
        g_arrowPosX = Lerp(startX, endX, t);

        if (t >= 1.0f)
        {
            g_stage = AnimStage::Cocking; g_timeInStage = 0.f;
        } // loop
    } break;

    case AnimStage::Done:
        // Not used anymore, but kept for completeness
        break;
    }

    // Request redraw
    InvalidateRect(g_hWnd, nullptr, FALSE);
}

// -------------------------------------------------
// Window procedure
// -------------------------------------------------
LRESULT CALLBACK WndProc(HWND hWnd, UINT msg,
    WPARAM wParam, LPARAM lParam)
{
    switch (msg)
    {
    case WM_CREATE:
        if (FAILED(D2D1CreateFactory(D2D1_FACTORY_TYPE_SINGLE_THREADED,
            &g_pFactory)))
            return -1; // abort window creation
        SetTimer(hWnd, TIMER_ID, TIMER_MS, nullptr);
        g_prevTick = std::chrono::high_resolution_clock::now();
        return 0;

    case WM_SIZE:
    {
        g_windowW = static_cast<float>(LOWORD(lParam));
        g_windowH = static_cast<float>(HIWORD(lParam));

        // Update dependent geometry values
        topY = 120.0f;
        bottomY = g_windowH - 120.0f;
        midY = (topY + bottomY) * 0.5f;
        halfHeight = (bottomY - topY) * 0.5f;

        if (g_pRenderTarget)
            g_pRenderTarget->Resize(
                D2D1::SizeU(static_cast<UINT>(g_windowW),
                    static_cast<UINT>(g_windowH)));
    }
    return 0;

    case WM_TIMER:
        if (wParam == TIMER_ID)
            UpdateAnimation();
        return 0;

    case WM_PAINT:
    {
        PAINTSTRUCT ps;
        BeginPaint(hWnd, &ps);
        OnRender();
        EndPaint(hWnd, &ps);
    } return 0;

    case WM_DESTROY:
        KillTimer(hWnd, TIMER_ID);
        DiscardDeviceResources();
        SafeRelease(&g_pFactory);
        PostQuitMessage(0);
        return 0;
    }
    return DefWindowProc(hWnd, msg, wParam, lParam);
}

// -------------------------------------------------
// WinMain - entry point
// -------------------------------------------------
int WINAPI wWinMain(HINSTANCE hInst, HINSTANCE, PWSTR, int nCmdShow)
{
    const wchar_t CLASS_NAME[] = L"BowWindow";

    WNDCLASS wc = {};
    wc.lpfnWndProc = WndProc;
    wc.hInstance = hInst;
    wc.hCursor = LoadCursor(nullptr, IDC_ARROW);
    wc.lpszClassName = CLASS_NAME;
    RegisterClass(&wc);

    g_hWnd = CreateWindowEx(0, CLASS_NAME, L"Direct2D - Longbow Demo",
        WS_OVERLAPPEDWINDOW,
        CW_USEDEFAULT, CW_USEDEFAULT,
        static_cast<int>(g_windowW),
        static_cast<int>(g_windowH),
        nullptr, nullptr, hInst, nullptr);

    ShowWindow(g_hWnd, nCmdShow);

    // Main message loop
    MSG msg;
    while (GetMessage(&msg, nullptr, 0, 0))
    {
        TranslateMessage(&msg);
        DispatchMessage(&msg);
    }
    return 0;
}