.shadow-rainbow:after{background:linear-gradient(90deg,#44ff9a -.55%,#44b0ff 22.86%,#8b44ff 48.36%,#f64 73.33%,#ebff70 99.34%);content:"";filter:blur(50px);height:30%;left:0;position:absolute;right:0;top:40%;width:100%;z-index:1}button.shadow-rainbow:before{background:#fff;border-radius:inherit;content:"";height:100%;position:absolute;right:0;top:0;width:100%;z-index:2}