Just you and your little dot against the music, and it's glorious.
The game eases you into the nasty stuff, but doesn't take long to do so. Slow down and half speed modes make those nasty spots a little easier, but only just a little. Though things slow down, the bullet keep appearing, so there is more stuff on the screen to avoid. Use it sparingly, as the game itself recommends. This game plays with the turntable aspect nicely too, even making the pieces move backward when the music slows and starts reversing. Watch out :)
Another nice feature is that though you have to unlock newer levels, it doesn't make it difficult to do so. Getting scores in the 80%+ range on each level locks another level or two. Getting 80% is actually pretty easy to do, even if you get hit one or two times. But, you'll probably want to replay most levels until you get the 100%. Also, complete level editor - make your own, with your own music.
Controls? Pick your poison: WASD, mouse and game controller all supported.
If you like bullet hell games, mixed with a variety of music (mostly trance/dance/chiptunes/etc), this is well worth buying. At full price even. But, if it's on sale, most definitely.