A great, and very long puzzler.
The game is pretty quiet as far as music goes unless you pick up a special temporary powerup such as invincibility, other than that the game is pretty quiet musicwise. The only sound is when you fire, die, or hit something.
Although you can move free-form around up, left, right or down, objects can still fall downward toward you, so you must get out of the way when something is falling toward you, unless you're fast enough to destroy it if it's breakable. Otherwise, don't take the time to try. There are all kinds of puzzles to solve, and usually something pretty new to you. It's definatally worth the try, but make sure you have a book or something to keep your passwords in, everytime you start a new level, the opening screen shows you the password, so write it down before going on. You may need it.
The difficulty varies depending on the level. Sometimes you have to speed through it to complete it. Other times it takes a bit of thinking and strategy just like any other puzzle. Give it a shot, you've nothing to lose!