Interesting... and catchy, too.
Well, the graphics are okay, but the animation is very smooth and helpt it a lot. The concept of the game is very simple, but nonetheless attracting. I got hooked up, which is good. ^_^
The sound is appropiate, the background music fills the space correctly, and the gun sound hears good.
I give more points for interactivity and style, since this game has both. Despite it's just clicking, you have to click on the correct time, i.e. you have to pay a lot of attention to the game and THAT is my concept on interactivity. ;-) That has style.
Overall: a really nice way to spend time. Keep it up!