Cool idea! Some stuff needed work.
Great first game. But if i hadn't known it was your first... i'd say it's just 'okay'.
The idea is fun. I enjoyed trying to beat the levels. However, your collision detection REALLY REALLY REALLY needs work. Don't go for the basic hitTest unless its a really small object. Make little collision boxes inside the character.
Also, the score thing... you can just walk against a wall. I don't really understand how the score system works... is counting their steps a really good way to do this? Perhaps you could have them start off with 100 points per level, minus 1 point every second or something. Same thing applies to jumping, on the first level.
The graphics were pretty good. I don't know if you made them, but if you didn't, you should try and make your own. It's much better that way, even if the graphics aren't quite as good.
The gameplay was fun overall. Again, the collision detection was a let down. Also, I found it slow... we want speeeeed. make it more fast paced!
I think you are really going somewhere with this. One last thing to suggest... the jumps... make them faster and more user controlled: the longer you press space the more he jumps (to a maximum, of course).
Good work. Can't wait to see your next game.