It will depend on how you have the game developed. If
everything is based on the playhead moving from frame to frame then
you could just do movieClip.stop();
But since you created a game, I'm assuming that this would be
too trivial of an answer. Without more info all I can say is that
you should create a _root level function that stops all current
animations, movieclip playheads, sounds, etc. Depending on the
complexity of your game this could be a lot of stuff.