Shatter is about bouncing a projectile between your paddle/ship/etc. and various blocks you need to break to progress to the next stage. Power-ups occasionally drop from said blocks, and there are different varieties. That's all pretty basic. What sets Shatter apart is the beautiful backgrounds and setpieces in the game, as well as the unique features it adds. The most obvious is your ability to push away or draw in objects as you play, including the ball, the pickups, the fragments (points), and sometimes the blocks themselves. At first it's merely a nice feature for adjusting the path of the ball mid-flight, but later it becomes necessary to really properly progress through the game. Fortunately, Shatter does a good job of ramping up the necessity of using these features, so by the time you truly need to it's natural.
Another somewhat unusual feature is the concept of boss fights, not totally unseen in a block-breaker clone but rarely done well. Shatter does it quite well, I'm happy to say, and thanks to the aforementioned beautiful design of the game the bosses are visually satisfying in addition to challenging. The mechanics of each boss fight are similar but not identical, making you target specific vulnerable points while dodging whatever attacks the boss is capable of. The fights are also spaced evenly between the levels, giving you a nice change of pace to break up any monotony that might set in.
Difficulty wise, the game is not easy but not especially hard for an experienced player... at least when it comes to just surviving the game. If you want to rack up the high scores, well that will take some serious skill. The game's scoring system is simple on paper but hard to master, relying on a multiplier which increases with gathered fragments but decreases for any blocks which slip past your paddle or make contact with it (yes, they can do that). It provides a reason to replay the game for people who are all about the high scores, made even more attractive with the game virtually taunting you by showing you higher scores from any of your friends who also play the game. Devious, but effective.
Beyond all that the game is quite solid, featuring some unique types of blocks, interesting mechanics, varied arena shapes including circular, and a fun bonus round after each area where you have to keep three projectiles in the arena for as long as possible. I also really have to compliment the game's music, which is both fitting and kind of catchy. If you have any love for Kavinsky or Daft Punk you'll probably like the soundtrack.
Shatter is a fresh take on an old formula, one that adds some interesting new concepts without straying too far from the basic idea. It hits that perfect line of "easy to pick up yet difficult to master", and provides something you can either spend hours on or just pick up for a few minutes at a time.