programming buttons

Thanks man, i get whats going on there i thought there pretty much what i was thinking. but this line

Method HitTest:Int(hitX:Float, hitY:Float)
	Local pix:Int = ReadPixel(_pixmap, hitX, hitY)
	If pix & $FF000000 Then Return True
End Method

I got some of this, but just so i understand could you explain how the hit test works?