button{padding:1rem 2rem}.btn-filler{position:relative;overflow:hidden}.btn-filler span:first-of-type{mix-blend-mode:difference;color:white;position:relative;z-index:10}.btn-filler.--inverse .filler{background-color:black}.btn-filler .filler{display:-webkit-box;display:-webkit-flex;display:-ms-flexbox;display:flex;background-color:black;width:0%;height:0%;-webkit-border-radius:50%;border-radius:50%;-webkit-transition:1000ms;-o-transition:1000ms;transition:1000ms;-webkit-transform:translate(-50%, -50%);-ms-transform:translate(-50%, -50%);transform:translate(-50%, -50%);position:absolute;z-index:5}.btn-filler .filler.--filling{width:300%;height:300%}.btn-filler.--active span:first-of-type{mix-blend-mode:unset}