Тетрис в консоли: почему выбрасывается исключение?

Необработанное исключение по адресу 0x01037454 в TETRIS_K.exe: 0xC0000005: нарушение прав доступа при записи по адресу 0x003BB000.

#include "stdafx.h"
#include<conio.h>
#include<iostream>
using namespace std;
#include<windows.h>
 
 
 
wstring tetromino[7];
int nFieldWidth = 12;
int nFieldHeight = 18;
unsigned char*pField = nullptr;
 
int nScreenWidth = 80;
int nScreenHeight = 30;
 
 
int Rotate(int px, int py, int r)
{
 switch (r % 4)
 {
 case 0: return py * 4 + px; //0 degrees
 case 1: return 12 + py *-(px * 4); //90 degrees
 case 2: return 15 - (py * 4) - px; //180 degrees
 case 3: return 3 - py + (px * 4); //270 degrees
 }
 
 return 0;
}
 
bool DoesPieceFit(int nTetromino, int nRotation, int nPosX, int nPosY)
 
{
 for (int px = 0; px < px; px ++)
 for (int py = 0; py < 4; py++)
 
 {
  //Get index into piece
  int pi = Rotate(px, py, nRotation);
  // get index into field
  int fi = (nPosY + py)*nFieldWidth + (nPosX + px);
 
 
 
  if (nPosX + px >= 0 && nPosX + px < nFieldWidth)
  {
   if (nPosY + py >= 0 && nPosY + py < nFieldHeight)
   {
 
    if (tetromino[nTetromino][pi] == L'X'&& pField[pi] != 0)
     return false; //fail on first hit coolision detection
   }
  }
 }
  
  return true;
}
 
int main()
{    // Create assets
 tetromino[0].append(L"..X.");
 tetromino[0].append(L"..X.");
 tetromino[0].append(L"..X.");
 tetromino[0].append(L"..X.");
 
 
 tetromino[1].append(L"..X.");
 tetromino[1].append(L".XX.");
 tetromino[1].append(L".X..");
 tetromino[1].append(L"....");
 
 
 
 tetromino[2].append(L".X..");
 tetromino[2].append(L".XX.");
 tetromino[2].append(L"..X.");
 tetromino[2].append(L"....");
 
 
 
 tetromino[3].append(L"....");
 tetromino[3].append(L".XX.");
 tetromino[3].append(L".XX.");
 tetromino[3].append(L"....");
 
 
 
 tetromino[4].append(L"..X.");
 tetromino[4].append(L".XX.");
 tetromino[4].append(L"..X.");
 tetromino[4].append(L"....");
 
 
 tetromino[5].append(L"....");
 tetromino[5].append(L".XX.");
 tetromino[5].append(L"..X.");
 tetromino[5].append(L"..X.");
 
 
 tetromino[6].append(L"....");
 tetromino[6].append(L"..XX");
 tetromino[6].append(L"..X.");
 tetromino[6].append(L"..X.");
 
 
 pField = new unsigned char[nFieldWidth*nFieldHeight];
 for (int x = 0; x < nFieldWidth; x++) //Boeard Boundary
 for (int y = 0; x < nFieldHeight; y++)
  pField[y*nFieldWidth + x] = (x == 0 || x == nFieldWidth - 1 || y == nFieldHeight - 1) ? 9 : 0;
 
 
 wchar_t * screen = new wchar_t[nScreenWidth*nScreenHeight];
 for (int i = 0; i < nScreenWidth; i++) screen[i] = L' ';
 HANDLE hConsole = CreateConsoleScreenBuffer(GENERIC_READ | GENERIC_WRITE, 0, NULL, CONSOLE_TEXTMODE_BUFFER, NULL);
 SetConsoleActiveScreenBuffer(hConsole);
 DWORD dwBytesWritten = 0;
 
 bool bGameover = false;
 
 int nCurrentPiece = 0;
 int nCurrentRotation = 0;
 int nCurrentX = nFieldWidth / 2;
 int nCurrentY = 0;
 
 
 while (!bGameover)
 {
 
  //GAME TIMING ==========================
 
 
  ////////
 
 
 
 
  // INPUT ======================
 
 
  //GAME LOGIC =============================
 
  //RENDER OUTPUT
 
 
  //draw field
 
  for (int x = 0; x < nFieldWidth; x++)
  for (int y = 0; y < nFieldHeight; y++)
   screen[(y + 2)*nScreenWidth + (x + 2)] = L" ABCDEFG=#"[pField[y*nFieldWidth + x]];
 
    //Draw Current Piece
  for (int px = 0; px < 4; px++)
  for (int py = 0; py < 4; py++)
  if (tetromino[nCurrentPiece][Rotate(px, py, nCurrentRotation)] == L'X')
   screen[(nCurrentY + py + 2)*nScreenWidth + (nCurrentX + px + 2)] = nCurrentPiece + 65;
 
 
 
 
  // Display Frame
  WriteConsoleOutputCharacter(hConsole, screen, nScreenWidth*nScreenHeight, { 0, 0 }, &dwBytesWritten);
  system("pause");
 }
 return 0;
}

for (int y = 0; x < nFieldHeight; y++)