Add the digits. Find results as fast as you can. Think you're smarter than Mister Mind? Add two digits kids online game. Games designed to help children understand basic number concepts. Discovered games, quickly and play ... faster and soon became a challenge to yourself -- how quickly can You add two digits in your head? Those who can add two digits and those who can add three digits ... will then be brought together in a group to solve a math problem in a game.