Important Formulas in This Chapter

Obviously, the big formula here is gravity.

Basic gravity:

 force = G * m1 * m2 / distance  2  

ActionScript-friendly gravity implementation:

 function gravitate(partA:MovieClip, partB:MovieClip):Void {       var dx:Number = partB._x - partA._x;       var dy:Number = partB._y - partA._y;       var distSQ:Number = dx*dx + dy*dy;       var dist:Number = Math.sqrt(distSQ);       var force:Number = partA.mass * partB.mass / distSQ;       var ax:Number = force * dx / dist;       var ay:Number = force * dy / dist;       partA.vx += ax / partA.mass;       partA.vy += ay / partA.mass;       partB.vx -= ax / partB.mass;       partB.vy -= ay / partB.mass; }