Doing the same thing over and over felt a bit sameish. Maybe a longer level, where you had to collect treasure in several places before returning would have been more fun. The sound effects worked well, but you could have added some music. Or maybe some sound effect that plays when the highscore table shows.
While the there-and-back theme is there, I think it would be more interesting if something changed when you collect the treasure. Maybe it could randomly create a hole in the bridge that you have to jump over (just make sure the bat can't stay above that hole for too long, since I assume jumping into the bat should cost a life). But it was fun to play for a short while.
And one thing I really liked was that the menu could be controlled with either the keyboard or mouse.