ORBITAL

Overview

Orbital is a puzzle shooter developped by Bitforge for the iphone and ipod touch. It's 1.99$ in the app store. 
Gameplay 
In Orbital, you fire balls that bounce against the wall and expand. Depending on where they stop bouncing, their size varies. For exampple, if the ball ends up in a corner, it wil be relatively small. If it ends up in an open space, it can be huge. You fire the cannon from the bottom of the screen and if thee ball bounces back, crossing the red line that's in front of the cannon, it's game over. 
 
Once the ball expands, a number appears in the center of it. This number corresponds to the number of times that you must hit it before it disappears. Each ball starts with the number 3 in the middle. The fact that you can only eliminate a ball with another ball creates an endless chain of balls. The way you eliminate the nalls depends on the game mode. 
 
Gravity mode, as the name suggests, involves gravity. Here, each ball serves as a planet with its one center of gravity. When you fire your ball, it will be attracted to the other balls. The strength of the gravity depends on the size of the ball and the fact that the ball you fire is magnetized to the bigger balls lets you eliminate them alot quicker. 
 
Pure mode is a more classic mode with no gravity in play, just simple gameplay where you must hit the other balls to make them disappear. Super Nova mode has you directly controlling the canon. A laser shows you where the ball will end up but since there's gravity in play, you must take into account that what you're being shown may not be the actual path of your ball. There is also a two player mode.