Simple but effective – the way a puzzle game should be.
Each block has a little line running from left to right. The lines can be straight or bend, but will always touch two corners of the block it's in. You can move each block up and down, and swap them with a block above or below it, but you can't move the blocks side to side. The point to make a connecting line from one side of the board to the other. It's deceptively simple and gets both addicting and challenging.
The speed of the games varies allowing you some time to try and catch up when your board begins to fill with lines that you haven't connected yet. But at the times when the pace picks up it can get pretty crazy. All the while you'll be doing your best to make the longest connection possible to rack up more points and move along the stages more quickly.
As your progress you'll unlock new boards, or more specifically backgrounds to the boards. The backgrounds have no direct impact on the game-play mechanics. They're more of a skin than anything, but each has it's own unique look, music, and sound effects. Some of the visuals that are going on in the background can be distracting however, adding a level of challenge that I was at times questioning if it was intentional.
The game turned out to be quite a bit of fun for me, but it's the number of levels that gets overwhelming. My longest run lasted about half and hour, and I didn't even make it through half the number of stages there are. But when you play through the game to unlock levels you always start from the beginning and there's no mid-game saves, so if you want to unlock all the levels, as far as I can tell, you'll be busy for a couple hours straight. It doesn't really seem conducive to hand-held gaming.
There is a save feature of course once you do unlock new boards to play. You can then play a game that takes place on just one or two boards for the entire time (of course you will not unlock any new boards when you take this route). The trouble with the save feature is that it's not an auto-save and you have to go through a couple menus to get to it. More than once I have forgotten to save my progress before shutting my PSP down, having been spoiled by games that save for you.
So the likelihood that you'll see all the game has to offer I think would require a lot of dedication. The intense visuals and constant action that keeps your fingers twitching may have you taking a break between sessions. But the colourful, bright, energetic levels most people can probably manage to unlock should keep you busy for some time. And with the game-play becoming easily addictive, you'll want to revisit the title to try for new high scores.