If Tetris and Bejeweled were to have a child, they would give birth to FLIP. This is a puzzle game of flipping and tilting your iPhone around to manipulate gems. There are 3 very distinct game modes: standard, puzzle, and speed.
In standard mode, gems fall one at a time from the top and the objective is to mach like-colored gems by having them touch. Tilting the iPhone left and right moves the falling gems appropriately. These controls are fairly sensitive and it's easy to move a gem farther than intended. I found that the more vertical I hold the iPhone, the less sensitive the controls tend to be. If you flip the iPhone 90 degrees, all the gems will fall to the new bottom. This is what makes standard mode a true puzzle in my opinion. For example, in the above screenshot, it initially looks like there's no way to match 4 gems. But if I flip to the right, I will get 4 red gems to match up. This makes the dynamics of the game interesting and challenging. As you progress, the falling speed and the amount of gems you need to match increases. You get bonus points for multiple matches at once called "link combos" and for matching more gems than required for that level. The game ends when a gem is unable to enter the game because the stack is too high.
In this mode, you play through a series of what eBattalion calls "think-puzzles". Each level begins with multiple distinctly colored gems in a specific location. On the grid, there is a colored square for each gem. The goal is to get the gems to their matching square. When you get a match, the square eats up the gem and turns white like the rest of the grid. You're given a certain number of allowed flips to complete each level. If you finish without using all the allotted flips, you earn extra points. If you do not complete the puzzle with the allowed flips, you lose a life. The game ends when you lose all your lives. You are also given a certain amount of continues. Using a continue lets you continue from the current level, but erases your points.
To control the gems, you must (of course) flip your iPhone around. Moving gems square by square is not an option; they all fall in the direction that you tilt your iPhone. Again, the controls are pretty sensitive and it's easy to accidently make unintended moves. I found it easiest to play this mode with my iPhone as flat as possible looking down on it.
The object of this mode is to match up all the like-colored gems in each level before you run out of time. What makes this mode challenging is that you must have all the gems of one color matched up before they clear. The controls and layout is exactly like puzzle mode. The quicker you complete the level, the more points you get. The game is over if you do not complete the puzzle in time. Unlike puzzle mode, you do not have any lives. You can use continues, however, but this erases your points.
FLIP is a great little game (actually, three games), especially at only $0.99. I find myself playing when I have a few minutes to kill as well as when I have time to obsess over it for awhile. I would love it if a future update had an option to adjust the sensitivity of the controls. I often find myself losing a life or game because the game reacts when I barely move. I was initially disappointed that there wasn't an option to disable the accelerometer and have gesture controls, but it didn't take long to realize that the game wouldn't be the same with gestures... besides, its name is FLIP for a reason!
FLIP is available for $0.99 from the iTunes App Store.