A free app for Android, by Huesoft.

Are you looking for a fun way to test your mental agility? If so, ABC Challenge is the perfect app. It improves your memory and reflexes by getting you to match the numbers and letters appearing on the screen as quickly as possible. The more you practice, the faster and more accurate you will become! You get to race against another player while the clock is ticking and see how fast each player finds all the letters that have the same color as their button and challenge each other. The game is simple but mind-boggling. You will learn to pay attention and focus on your test as you enjoy increasing levels of difficulty. Be proud of yourself for completing this great challenge!