I like it :D
I like the music
This would be better if it had a bit more of... extra contents
Did I wake up in some parallel dimension where people consider this type of thing to be enjoyable? Half a star, because I kind of enjoyed the music.
I think that's the best way to describe it. It's an interesting concept, and with further development, I could imagine a game like this being successful, but as it is, the game is bland and uninteresting.
One way you could improve is, as Cyberleon suggested, adding some kind of backstory to the game. Everyone loves a backstory, even if it's nonsensical or poorly written (just look at Seed of Destruction's backstory), and adding one would compel people to play the game, if only to find out what happens next in the story. Also, the gameplay needs more; I grew very bored very quickly with simply lining up numbers and clicking. On my second play-through of the game, i managed to score 755 points, and I don't really play many FPS's on the computer. Increase the difficulty of the game and alter the gameplay to make it more exciting.
Here's an example of a way you could do so:
You are 'the world's best sniper'. You've been hired to protect a client (maybe the president, or maybe a bad guy, who knows?), and everything seems to be going smoothly, until suddenly you are ambushed by a whole swarm of enemies. Now you have to use your marksmanship to protect your charge(s)... by shooting down the bullets, grenades, missiles, and enemies that attack!