Nice Concept, yet outdated techniques
I didn't rate this too high, for there are several things about this game that don't seem to actually fit the genre. But I'll start off with the things I liked. You had a very good concept actually. The whole bear on moon and aliens thing is pretty funny. But that's about the only good thing there is to say, actually.
First thing I missed was a preloader. Given, your game is probably not among the huge file sized ones, still. Adding a preloader to your projects has become quite common. Second, the framerate. 12FPS has been abandoned a long time ago, set your framerate to 24+ to achieve fluid animations and a better gamestream. The Intro was incredibly boring, lacking of sound or music (as the whole game is). How about a short movie with the bear in his rocket crashing on the moon, getting surrounded by aliens? I mentioned the lack of sounds already, but there's more to come. I think you put the most of your work in the drawings and animations. I'm not a too good drawer myself, but I think you could have done a little better. Only a small minus though. What was really disturbing was the jumping function. A few more variables concerning the y velocities could have created a very good jumping effect that actually seems somewhat real. You're just putting the bear in the air though, which also gets very disturbing when you meet some aliens in their UFOs. And last but not least, you could have killed the timer, or at least make power ups give you more time.
All in all, this wasn't too exciting I guess. Concerning the fact that you're only starting off though, I guess you've tried your best. And that's what creating flash games is all about. It doesn't matter wether you're a good artist or scripter, as long as you keep trying, you can manage to improve this project and your future ones.
Good luck on your way!