While Flash has been used for animation and interactivity (as well as simply to annoy!), be aware that Flash is looking more and more like a dead end. While there's enough of an install base of Flash usage and players out there that it won't disappear overnight, HTML5 may become the method of choice. Witness the battle between Apple and Adobe over Flash vs. HTML5 in Apple products. As a developer, it would be foolish to ignore HTML5 and assume that Flash is here to stay.