Use this.gotoAndPlay() not gotoAndPlay()
Put ‘this’ in front of gotoAndPlay() methods called within a class that extends ‘MovieClip’.
This doesn’t just apply to gotoAndPlay there are few MoveClip methods that tend to go a bit qwerky if you don’t include the ‘this’.
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If anything is unclear or just plain wrong let us know and should ammend it pretty sharpish. If you visited the page with a particular question leave it and if it's flash related I'll try to answer it.