Choose a number, find it, mark X's, then switch
Find and Mark! is a two-player number-search race. One player finds the called number while the other marks their page; the roles switch, and the first player to fill the page wins.
The full official description, verbatim from the game page: “You or your Opponent chooses a number! … While one finds a number, the other Marks their page with X's … Switch turns once the number has been found! … Fill up your page before your Opponent or LOSE! … Be quick in finding the number as well as marking the page!!” That single paragraph is the entire rulebook the studio publishes — everything else on this wiki is either API data or labelled player technique.