KNOWN PROBLEMS

- Clipping sometimes fails, i.e. you can walk through walls or get stuck
- There's a problem with flying monsters. They sometimes get stuck
  in the wall or will stick at the top of the screen an won't go
  away until a new level is entered. Sometimes, the game gets  completely
  corrupted; the player may end up in the wall with the monster and die.
- There is a problem with C++ destructors not being called because they
  are not declared "virtual" when the actually should. E.g. in 
  CApplication::UnloadLevelData(), instances of different subclasses of
  CThing are deleted through a CThing pointer; as a result only 
  CThing::~CThing() is actually called, but not the destructor of the
  actual subclasses. Unfortunately, there seem to be bugs in some of those
  destructors. When just declaring CThings's of even CObject's destructor 
  virtual, the game becomes very unstable and crashes on changing between
  different levels.