◇ Just read — no move neededThe loaded silence
空头炮 — the hollow-file cannon — sits on the king's file with nothing between them. By itself it checks nothing: a cannon needs exactly one screen. Its power is the threat: the moment any piece appears on that file, the cannon fires through it at the king. Every black piece is forbidden from the file; the king's own advisors become jailers keeping him away from his best defence. And when you can place the screen yourself, the hollow file converts instantly.