Brain Age: Train Your Brain in Minutes a Day! (Japanese: ブレインエイジマインドを鍛える15分間トレーニング, Brain Age: 15-minutes Mind Training) is an educational puzzle video game developed and published by Nintendo for the Nintendo DS handheld game console. The game was released in Japan in December 2005 and in North America and Europe in April 2006. Brain Age is designed to be a mental exercise program, meant to improve the user's mental agility. The game uses simple mathematical problems and puzzles to determine the user's 'brain age,' which is represented by an average of the user's results in the various puzzles. As the user continues to use the game, their brain age should decrease as their mental agility increases. The game features several different activities, such as math problems, memory games, reading exercises, and shape recognition. The game also features voice recognition, allowing the user to speak the answers to certain puzzles instead of writing them down. Brain Age also features a 'Daily Training' mode, which allows the user to attempt a variety of puzzles each day and track their progress. Brain Age was a success, selling over 19 million copies worldwide. It was followed by two sequels, Brain Age 2: More Training in Minutes a Day! and Brain Age: Concentration Training. The series has become one of Nintendo's most successful franchises, and has been praised for its educational value.