Firstly

Download The Caurina Tweener. Available from code.google.com. And place it in the folder where your flash file is. Open Flash, Then AS2 Flash Document. On the first line of actionscript insert the following code:

import caurina.transitions.Tweener;


This imports the class to use in our application. Then...

var base:Object = this;


This is a root identification variable that allows us to use variables from the root level without any hassle.

Secondly

Create a random movie clip and fill it in with a square or whatever shape you like. Give this movieclip the instance name of fullscreen_button

Thirdly

This is the function.

// Main Function called fullScreenSetup
var fullScreenSetup:Function = function () {
// Uses Caurina Tweener To Give a RollOver Effect
base.fullscreen_button.onRollOver = function () {
Tweener.addTween(this, {_alpha:50, time: 1, transition:"easeOutExpo"});
}
// Reset's the animation when roll out.
base.fullscreen_button.onRollOut = function () {
Tweener.addTween( this, {_alpha:100, time: 1, transition:"easeOutExpo"});
}
// When pressed, it runs an if statement.
base.fullscreen_button.onRelease = function () {
// If the stage is normal, fullscreen is activated. If not nothing happens.
if (Stage["displayState"] == "normal") {
Stage["displayState"] = "fullScreen";
} else {
Stage["displayState"] = "normal";
}
}
}


Finally

To initiate this function simply place this code whereever you want the function to run.

fullScreenSetup();


NOTE: Make sure your html document allows fullscreen mode otherwise it won't work.