I read the instructions, clicked on a lot of asteroids and was victorious! It was cool!
One thing I didn't understand was if the asteroids that were going off the screen were being counted or not. It seemed like they weren't, or I didn't get enough visual/sound feedback on it. It is very hard for someone with tunnel vision like me to see if the timer is getting increased/decreased every moment lol maybe a little animated "-2" where they leave the main screen?
Overall, I like the idea and I agree that it would be a good touch game!
Keep up the excellent work!