From Peter Li:
Test and train your subtraction speeds in only 2 minutes a game! New LEVEL UP system: The more you solve the harder it gets! Share results with family, friends and the rest of the world. Leaderboards & Achievements included (Game Center) Features: - The all new LEVEL UP system will challenge you! - Stylish and intuitive user interface - Subtract numbers from as fast as possible - Share scores with family and friends - Challenge everyone on Leaderboards & Earn all Achievements (Game Center) How to play: 1) Subtract numbers together for 2 minutes. 2) For every 8 correct answers, you LEVEL UP and increase the difficulty. Find out who among you is a Subtraction Master!