Silver ball means that if one side doesn't score within 15 minutes after the lead, the leading side wins the 2004 European Cup.
Either way, the maximum overtime time is 30 minutes (excluding overtime). If you can't decide the outcome, you need to shoot penalty shoot-out at the other side.
Because it is found that the first two methods are too accidental in application, now almost all games use the method of overtime for 30 minutes, including this World Cup.