In the quiz show based on the famous pencil-and-paper game, contestants answer questions in various categories to put up their respective symbol, X or O, on the board. The goal of the game was to complete a line of three X or O markers on a standard tic-tac-toe board (with the reigning champion always using X's and going first). Each of the nine spaces on the gameboard featured a category. Contestants alternated choosing a category and answering a general interest or trivia question in that category. If they were correct, they earned an X or O in that square; otherwise, it remained unclaimed. The center square, being of the most strategic importance, involved a two-part question, with the contestant given 10 seconds to think of the two answers needed to win the square (though in the 1950s version, the contestant could opt out of the extra time). After each question, the categories shuffled into different positions (in the 1950s series and early in the 1978 revival, the categories shuffled only after both contestants had taken a turn). In the 1990 series, the categories shuffled prior to the start of each contestant's turn and the shuffle was stopped when the contestant in control hit his/her lock-in button. If it became impossible for either contestant to form a winning line, whether or not all nine spaces had been claimed, the game was declared a draw and a new one began. The process continued until the deadlock was broken, however long it took to do so. This meant that a match could take multiple episodes to complete, which happened quite often. Tic-Tac-Dough used a rollover format, which allowed a new game or match to start at any point during an episode, continue until time was called, and then resume on the next episode with the same categories in play. Later in syndication during the 1980's the show would introduce the "Chase the Dragon" Bonus Round to end the game.