You are in control of the ship. You can move it left and right, to let it hover over another lane. In the picture above, for instance, the lanes are coloured red, orange and blue.
When hovering over one of these lanes, you will notice dots on them. On the blue lane for example, you see them being yellow. Those dots are actually targets, and your goal is to shoot them all without missing one. Sounds easy enough, no? The catch is that the targets are aligned to either be on the left side of a lane, in the middle of a lane, or on the right side of a lane. On the blue lane in this picture, you can clearly see the pattern being [ left, right, left ] each time. You need to hit the right buttons in order to be able to shoot down the targets.
The targets are placed on the rhythm of the music. That should make things a bit easier for you. The music of a lane will only play if you’re shooting down all the targets in the right way (ie: not missing one). If you succeed to do that for a while, the lane blows up and the music associated with that lane will play on. For the red lane, that music is usually the drums section. After having shot down a lane, I suggest going to try an other available lane as soon as possible, to rack up your score. Each consecutively succesful destroying of a lane not only gives you points for all the targets you hit, but also increases the multiplier, making your score even higher!
Now, there are also powerups available in the game. These are: autoblaster, freestyle and scoredoubler. Autoblaster destroys an entire lane for you. If you failed a lane, and use the autoblaster to destroy it anyway, you’ll get your old multiplier back (yay!). Freestyle is you scratching on the touch-screen to get points and creating a nice melody yourself. Scoredoubler is exactly what you’d expect it to be; it doubles the scores you’d otherwise receive for a short time.
That’s it. If you want to know more about the concept, please read FAQs and such on the game on which AmplituDS was based on. That should help out. Maybe one day, I’ll put a quick video of this game online as tutorial.