Kind of a fun concept. The player can in a way adjust the difficulty of the game while playing, by being able to control time like that. It gave a funny bullet-time sort of effect, by slowing time way down, shooting a bunch of times and then speeding up time again afterwards. I tried playing at a speed of 1.4, and managed to get a score of 65, but boy it was difficult! It would be cool if you added some sounds and a soundtrack to the game, I think that would add a lot to the overall experience.
All in all, well done! A simple but straight forward game :-)