Concentrate is not available in Google Play, and is normally priced at $0.99 in the Amazon Appstore. As we've noted before, there are sometimes differences in pricing and availability between the two marketplaces.
Concentrate is described as follows:
Concentration is a classic memory game using a 52-card deck. If you enjoy playing memory card games, but feel you've outgrown matching cartoon animal faces and fruits, Concentration offers a more aesthetically age-appropriate version of the game you've always loved--but you're five-year old can still play it too.Concentrate is rated at 2.7 stars in the Amazon Appstore.
Flip and Match
The cards are dealt out face-down. The player picks two cards and tries to find a match in rank. If they match, the cards are removed from the game. Otherwise they are flipped back over. The game ends when all cards are removed.
High Scores and Best Time
The simple touch interface allows you to flip cards with a touch of the finger. Compete for the highest score and best time with everyone in the family. Concentration is simple, entertaining, familiar, and great for warming up your memory muscles.
Issues include force closing, and that the app doesn't work on a Galaxy Nexus, which is a stock Android phone. We'd pass on this app.
what it means to developers.
Amazon.com opened up the Appstore despite a lawsuit by Apple, which has previously trademarked the term "App Store." Microsoft has filed an appeal against that trademark, saying the term is too generic. Amazon.com has responded to the lawsuit in the same manner.