As I mentioned above,
Tidalis isn't the standard block-based puzzle game. While colored tiles do fall from the sky, you have no control over where they land or when they appear. Each tile is a color and has an arrow on it. The goal is to line up the arrows so that they will lead to large combos and destroy as many blocks as possible. When you feel like you've lined up a good set, a click of the mouse activates the wave and sends it from your selected tile in whichever directions your blocks say for it to go. As it bounces around the board, it will not only follow your path, but it can also split if it crosses a double-headed arrow, thus making the possible number of blocks to hit staggeringly high with the right amount of strategy.
When the wave has run its course, the activated blocks go away, the ones above them fall, and they set off waves of their own. If you planed your maneuver well enough, then those subsequent beams will run around the board bouncing from tile to tile some more and allow you to rack up even more points. Of course, while you are doing this, tiles fall from the sky and fill up the game board, so you won't want to spend too much time setting up the perfect pattern.
Tidalis offers a few different gameplay modes. Not only is there an Adventure mode that narrates you through a strange island filled with strange animals, but there is also a Brainteaser option where you have a set number of moves to clear boards.
Tidalis also offers some online play and gives you the option to join or host games either on your local network or on across the world. With the game's Network Play, you can go Co-Op or Versus in any of the single-player levels, and offers a friend search to let you find players ranked anywhere from New Player to Insanely Good, and the games themselves range from Impossible to Lose to Impossible to Win. While an online feature is rarely seen in a puzzle game, it is a nice change of pace and it might even appeal to some of the casual gamers who will be intrigued by Tidalis.