Pivots is a fast, fun math game for iPhone

Pivots for iPhone (free with in-app purchase) is a clever little game that makes me question my addition skills. The premise is simple: arrange a row of numbers so that they add up to 15. Succeed and gain points. Fail, and lose time from the ticking clock. Here's our look at Pivots.

First off, Pivots is a nice-looking game. The four toolbar icons -- help, leaders, restore and share -- are minimal and convey their function clearly. The logo is cute, too, with a "heavy Sharpie marker" feel, and the friendly "Play!" button belies the tricky task at hand.

The game presents a 5x5 grid of single-digit numbers, all color-coded on a field of black (all 5's are yellow, 4's are purple and so on). As the game begins, you have 45 seconds to arrange rows so that they add up to 15. To arrange a row you may "pivot" an L-shaped, three-number section of blocks. Do so correctly and the new alignment will create at least one row of numbers that adds up to 15. You're rewarded with points and bonus time on the clock.

Get it wrong, and time is subtracted from the clock. You can reset the board at any time, but you'll suffer a 33% decrease in time for doing so.

Pivots features Game Center integration and a leaderboard, so you can challenge your friends. Finally, a one-time in-app purchase of $1.99 removes the ads that commandeer the screen after each game.

Fans of number games will enjoy Pivots. It's easy to learn and the app looks great. If you're like me with high English scores and low math scores, expect low Pivots scores, too.