Flashing Ninja

A simple game to see how well you can focus on objects. You will a 2 to 4 ninja switching positions in a 4x4 board. After flashing for a few times, you will need to find out where is the wanted ninja. The game will be come more and more difficult when you play. Totally you have 20 seconds for playing (timer will stop when ninjas are switching), and you earn 1 second for every correct answer. Note: pay attention to the text, not the text color because it may deceive you. Have fun, and see what is your highest score.