Sometimes the simplest of games can be the most enjoyable, challenging and addictive. Lines Classic from XIM Inc. isn't complicated but is entertainingly challenging. It's being offered over at the Windows Marketplace for free and that's a steal of a deal.

With Lines Classic you are presented a 9x9 board with colored balls randomly placed. The object is to move matching colored balls together to form a line of five or more. Once you accomplish that, the balls disappear and you earn points.

The twist is that every time you move a ball, three more are added to the playing field and you have to have a clear path to where you want to move the ball. You are given a little help in that above the playing board, the next three balls appear to allow you to better strategize moves.

Game interaction is simple. Tap the ball you want to move and then tap the destination square. In playing Lines Classic, I found it to be a stable application with no bugs, glitches or hangups experienced. There is an ad banner that runs across the bottom of the screen (to help make this a free app) but it's not distracting or overbearing.

If I had to find a fault with this game it would be that there are two shades of blue that are very similar. I've confused the two several times which cost me the game.

Lines Classic is a must have if puzzle games are your cup of tea. Lines Classic is currently available over at the Marketplace for free and hopefully it will make the jump to Windows Phone 7.