A chance game feature for a gaming machine is controlled by a processor in response to a wager. The feature comprises a matrix, a plurality of moving targets, and an object. The matrix defines an entrance end, an exit end, and a plurality of paths extending between the entrance end and the exit end....http://www.google.com.tw/patents/US6506114?utm_source=gb-gplus-share專利 US6506114 - Object drop feature for a gaming machine
