DropOut is a block-dropping color-matching puzzle game available exclusively for the iPhone and iPod Touch.
Slide the blocks by touching the rows and sliding your finger left or right. Blocks will disappear when four or more of the same color are touching. New blocks appear along the top and drop down to the game board. Some blocks have a lock on them. Any row that contains a Lock cannot be moved. Locks are eliminated when matched with other blocks of the same color, and they are worth more points than regular blocks. Falling Star blocks are worth the most points. Match four or more just as you would any other color. But be careful! They are called Falling Stars because if they reach the bottom row, they will fall through it and be lost. Whenever sets of matching blocks disappear, the blocks above them drop down to fill in the gaps. When falling blocks cause more matching sets to disappear, or if multiple sets of blocks are eliminated at the same time, you’ll get a combo bonus.
You’re in danger when the height of the blocks reaches the top row and the new set has no room to fall. When this happens, the top row will flash red for five seconds, and if the next row down is not cleared by then, it’s game over!
Source: The Developer Website.