If you've ever played casual games, there's a good chance you've played a game like the most recent addition to Xbox Live Arcade, Luxor 2. In fact, XBLA already has a similar title in Zuma Deluxe.
In simple terms, the premise is you have a shooter that fires colored balls, and you're aiming to put the ball you're firing into a group of like-colored balls. If you match three or more, they'll disappear from the chain. Even better is if that group of balls disappearing causes other like-colored balls to group, which gives you a bonus. The gameplay continues until you clear the board (for your victory) or when the balls reach the other end (for a Game Over).