by the way I would suggest you get rid of the ",就"so it becomes我在看电视的时候看到了我以前从没见过的一种游戏。which sounds more right to me,就is used when things are going the way less or earlier than you expect,like 他怎么就走了?(why is he already gone?)or 怎么就你一个,别人呢(why are you the only one,where is everyone else?)you don't need a 就 in the what you wrote 。