...but very basic, but it still kept me entertained for a half hour or so.
it would be nice if it had some music.
you could improve upon this by making the game harder as time runs out by either increasing the speed that the targets pop up, making the targets smaller, and mabey some other targets that will decrease your score as you progress.
could also mabey include upgrades, like using different wepons on the targets, and possibly power ups, like stopping the clock, larger targets etc.
all in all a good effort, and i hope some of my ideas help you improve on your next game.