To start a game, you'll need to tap on the "Tower Duel" option in the main menu. By doing so, you'll be paired up with a random opponent and from that moment on, you'll have six minutes to play. The goal is for you to get more categories than your opponent, for which you'll have 10 tries.
You'll see two towers, yours and your opponent's. In the lower part of the screen, you'll see six boxes that represent each of the categories of the game: History, Science, Geography, Art, Entertainment and Sports.
To compete for a category, you'll have to press on their respective boxes. Once you do that, you'll receive questions, and you'll have to try to answer as many as you can correctly and consecutively. If you get more right answers than your opponent, you'll win the character of that category and it will join your tower. If you don't answer correctly, you'll lose a life and you'll break your streak.
Keep in mind that you'll be able to use your tries as many times as you want in each category, which means that even if you earn a character, your opponent will be able to play in the same category to try to take it away from you.
If there's a tie in the number of characters of each player, the player with the most right answers will win.