body{color:#fff;background-color:#000;font-family:Arial,sans-serif;width:100%;height:100%}.overlay{max-width:400px;width:80%;margin:auto;padding:70px;z-index:1;position:relative}.fishtank{position:fixed;width:100%;height:100%;z-index:0}.littlefish{fill:#99f;stroke:none}.bigfish{fill:#f87;stroke:none}