-in the "lvl1" frame, on a new layer called "dude" create a circle for your dude....(other tutes have better ways to make him move....but this will suffice!)
-use F8 to make him into a movie clip and call his instance "dude"
- give him this action script...
Now your character will bounce off the walls...literally (WARNING! whatever you do... dont make your charecters speed higher than 10! unless you keep the amount you bounce higher than the characters speed, he will go through the borders otherwise)
(try it out, your dude should be able to walk around and not go through the borders)