Why does this...

#define WIN32_LEAN_AND_MEAN

#include<windows.h>
#include<windowsx.h>
#include<d3d9.h>
#include<d3dx9.h>

#define WINCLASS "winclass"

#define KEYDOWN(VK_CODE) ((GetAsyncKeyState(VK_CODE)& 0x8000) ? 1 : 0)

float a = 0.0f, b = 200, c = 400;
int d = 255;


float scaleIndex = 1.0f;

typedef struct 
{
	FLOAT x,y,z;
	DWORD color;
} sVertex;

#define VertexFVF (D3DFVF_XYZ | D3DFVF_DIFFUSE)

IDirect3D9 *g_D3D;
IDirect3DDevice9 *g_pD3DDevice;
IDirect3DVertexBuffer9 *pD3DVB = NULL;
IDirect3DTexture9 *pD3DTexture;
HWND windowhandle;
int windowclosed = 0;

int Game_Main();
int Game_Init();
int Game_ShutDown();
LRESULT CALLBACK WinProc(HWND hwnd,
						 UINT msg,
						 WPARAM wparam,
						 LPARAM lparam)
{
	switch(msg)
	{
	case WM_DESTROY:
		{
			PostQuitMessage(0);
			return 0;
		}break;
	}
	return DefWindowProc(hwnd, msg, wparam, lparam);
}

int WINAPI WinMain(HINSTANCE hinstance,
				   HINSTANCE hprevinstance,
				   LPSTR lpcmdline,
				   int ncmdshow)
{
	WNDCLASSEX winclass;
	HWND hwnd;
	MSG msg;
	
	winclass.cbClsExtra = 0;
	winclass.cbSize = sizeof(WNDCLASSEX);
	winclass.cbWndExtra = 0;
	winclass.hbrBackground = (HBRUSH)GetStockObject(BLACK_BRUSH);
	winclass.hCursor = LoadCursor(NULL, IDC_ARROW);
	winclass.hIcon = LoadIcon(NULL, IDI_APPLICATION);
	winclass.hIconSm = LoadIcon(NULL, IDI_APPLICATION);
	winclass.hInstance = hinstance;
	winclass.lpfnWndProc = WinProc;
	winclass.lpszClassName = WINCLASS;
	winclass.lpszMenuName = NULL;
	winclass.style = CS_OWNDC | CS_VREDRAW | CS_HREDRAW | CS_DBLCLKS;

	if(!RegisterClassEx(&winclass))
		return 0;

	if(!(hwnd = CreateWindowEx(NULL,
								WINCLASS,
								"Paintz",
								WS_POPUP | WS_VISIBLE,
								0,0,
								800,600,
								NULL,
								NULL,
								hinstance,
								NULL)))
		return 0;
	
	windowhandle = hwnd;

	Game_Init();	

	while(TRUE)
	{
		
		if(PeekMessage(&msg,NULL,0,0,PM_REMOVE))
		{
			if(msg.message == WM_QUIT)
				break;
			TranslateMessage(&msg);
			DispatchMessage(&msg);
		}

		Game_Main();
	}

	Game_ShutDown();

	return msg.lParam;
}

int Game_Main()
{
	if(KEYDOWN(VK_ESCAPE))
	{
		SendMessage(windowhandle, WM_DESTROY, NULL, NULL);
		windowclosed = 1;
	}
	if(windowclosed == 1)
		return 0;
	
	if(FAILED(g_pD3DDevice->CreateVertexBuffer(sizeof(sVertex)* 4, 0, VertexFVF, D3DPOOL_MANAGED, &pD3DVB, NULL)))
		return 0;

	if(d == 255)
		d = 0;
	else
		d++;

	sVertex Verts[4] = 
	{
		{ 2.5f, -3.0f, 0.0f, D3DCOLOR_XRGB(0, 0, d), },
	  { 0.0f, 3.0f, 0.0f, D3DCOLOR_XRGB(0, d, 0), },
	 { -2.5f, -3.0f, 0.0f, D3DCOLOR_XRGB(d, 0, 0), },
	};

	BYTE *ptr;
	if(SUCCEEDED(pD3DVB->Lock(0,0, (void**)&ptr,0)))
	{
		memcpy(ptr, Verts, sizeof(Verts));

		pD3DVB->Unlock();
	}

	
	if(FAILED(g_pD3DDevice->Clear(0,NULL,D3DCLEAR_TARGET,D3DCOLOR_RGBA(0,0,0,0),1.0f,0)))
		return 0;

	/*if(FAILED(D3DXCreateTextureFromFile(g_pD3DDevice, "grass.bmp", &pD3DTexture)))
		return 0;

	if(FAILED(g_pD3DDevice->SetTexture(0, pD3DTexture)))
		return 0;*/

	

	if(FAILED(g_pD3DDevice->SetFVF(VertexFVF)))
		return 0;

	if(FAILED(g_pD3DDevice->SetRenderState(D3DRS_LIGHTING, FALSE)))
		return 0;

	if(FAILED(g_pD3DDevice->BeginScene()))
		return 0;

	 D3DXMATRIX matRotateY;    // a matrix to store the rotation information
	  D3DXMATRIX matRotateX;    // a matrix to store the rotation information
	 D3DXMATRIX matRotateZ;    // a matrix to store the rotation information
    static float index = 0.0f; index-=0.05f;    // an ever-increasing float value

	D3DXMatrixRotationY(&matRotateY, index);

	D3DXMatrixRotationX(&matRotateX, index);

	D3DXMatrixRotationX(&matRotateZ, index);

	D3DXMATRIX matScale;

	
	scaleIndex -= 0.00f;

	D3DXMatrixScaling(&matScale, scaleIndex, scaleIndex, scaleIndex);
	if(FAILED(g_pD3DDevice->SetTransform(D3DTS_WORLD, &(matScale * matRotateY * matRotateX * matRotateZ))))
		return 0;

	 D3DXMATRIX matView;    // the view transform matrix

    D3DXMatrixLookAtLH(&matView,
                       &D3DXVECTOR3 (0.0f, 0.0f, 10.0f),    // the camera position
                       &D3DXVECTOR3 (0.0f, 0.0f, 0.0f),    // the look-at position
                       &D3DXVECTOR3 (0.0f, 1.0f, 0.0f));    // the up direction

    if(FAILED(g_pD3DDevice->SetTransform(D3DTS_VIEW, &matView)))
		return 0;// set the view transform to matView
	
	a += 0.1f;
		
    D3DXMATRIX matProjection;     // the projection transform matrix

    D3DXMatrixPerspectiveFovLH(&matProjection,
                               D3DXToRadian(45),    // the horizontal field of view
                               800 / 600,     // the aspect ratio
                               0.1f,    // the near view-plane
                               100.0f);    // the far view-plane

    if(FAILED(g_pD3DDevice->SetTransform(D3DTS_PROJECTION, &matProjection)))
		return 0;// set the projection

	if(FAILED(g_pD3DDevice->SetStreamSource(0,pD3DVB,0,sizeof(sVertex))))
		return 0;

	if(FAILED(g_pD3DDevice->DrawPrimitive(D3DPT_TRIANGLESTRIP,0,1)))
		return 0;

	if(FAILED(g_pD3DDevice->EndScene()))
		return 0;

	if(FAILED(g_pD3DDevice->Present(NULL,NULL,NULL,NULL)))
		return 0;

	/*if(FAILED(g_pD3DDevice->SetTexture(0, NULL)))
		return 0;*/

	return 0;
}
int Game_Init()
{
	if((g_D3D = Direct3DCreate9(D3D_SDK_VERSION)) == NULL)
	{
		return 0;
	}
	D3DDISPLAYMODE d3ddm;
	d3ddm.Width = 800;
	d3ddm.Height = 600;
	d3ddm.RefreshRate = 0;
	d3ddm.Format = D3DFMT_R5G6B5;
	D3DFORMAT d3df = D3DFMT_R5G6B5;
	if(FAILED(g_D3D->CheckDeviceType(D3DADAPTER_DEFAULT, D3DDEVTYPE_HAL,d3df,d3df, FALSE)))
	{
		return 0;
	}

	D3DPRESENT_PARAMETERS d3dpp;

	ZeroMemory(&d3dpp, sizeof(D3DPRESENT_PARAMETERS));

	d3dpp.Windowed = FALSE;
	d3dpp.SwapEffect = D3DSWAPEFFECT_FLIP;
	d3dpp.BackBufferFormat = d3ddm.Format;
	d3dpp.FullScreen_RefreshRateInHz = D3DPRESENT_RATE_DEFAULT;
	d3dpp.PresentationInterval = D3DPRESENT_INTERVAL_DEFAULT;

	d3dpp.BackBufferHeight = 600;
	d3dpp.BackBufferWidth = 800;

	if(FAILED(g_D3D->CreateDevice(D3DADAPTER_DEFAULT, D3DDEVTYPE_HAL, windowhandle, D3DCREATE_SOFTWARE_VERTEXPROCESSING,&d3dpp, &g_pD3DDevice)))
		return 0;

	return 0;
}
int Game_ShutDown()
{

	return 0;
}