This game is about being able to remember the previous picture N times back.
You start with 1-back which means the previous picture right before the one you see. If it is the same you click the match button. For example if the same Zebra picture is shown twice in a row you click the match button.
Then after 5 points you get to 2-back, here is where improving your fluid intelligence begins!
2-back means you have to remember the 2 previous pictures and click on match if they are the same.
Google Leaderboard and Achievements
Our other Memory Brain Games in this series:
PathCubes
Dual-N-Back-3D