This forum thread discusses the SitePoint article 'Build a Snow Boarding Game with Flash' by Matthew David.

..Good article but it doesn't take into account the coding conventions of flashMX. For instance it is suggested that you do not put you code directly into your MCs and Buttons but that all code be contained on layers within the MAIN timeline and target movie clips using dot syntax.

mymovieclip.onEnterFrame = function() {
// code
}

..and for a game like this you could use a more OOP approach to your actionscript.