i don't know about the "gravity" thing.
For the scrolling by moving the mouse, here are the basics:

You need to create a movieClip with the content you want to scroll.
Let's call this Movie Clip "photo" (instance name).
Then extend the MovieClip timeline acroos three frames. Create another
layer for your actions, with three keyframes:

keyframe 1:

yphoto = 0;
heightmovie = 471; //put here the height of your main flash movie
heightphoto = 820; //height of the scrolling content
scrollspeed = 15; //the higher the number, the slower the scroll speed

keyframe 2:

if (_xmouse > 0) {
ymouse = _ymouse - (heightmovie / 2);
speed = (ymouse) / scrollspeed;
if (speed < 0) {
speed = -(speed);
}
if (ymouse < 0) {
yphoto = yphoto + speed;
}
if (ymouse > 0) {
yphoto = yphoto - speed;
}

if (yphoto > 0) {
yphoto = 0;
}
if (yphoto < -(heightphoto - heightmovie)) {
yphoto = -(heightphoto - heightmovie);
}
setProperty("photo", _y, yphoto);
}

keyframe 3:

gotoAndPlay(1);




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