Need help with hittest and basic physics

hi

im making this jetski racing game and i need some help
with hit-testing.

http://www.arach.net.au/~tsg/jetski1.fla
http://www.arach.net.au/~tsg/jetski1.swf

ive got the movement sorted out, and
some very basic collision detection when you hit the
obstacles, but what i need to know is how to make it:

  1. stop when it hits the edges of the stage.
  2. maybe ‘bounce’ off the obstacles when hit,
    rather than just exploding…

and anything else you think i may need…

a big thanks in advance!