.glowing::before{content:'';position:absolute;left:-2px;top:-2px;background:linear-gradient(45deg,#e8f74d,#ff6600d9,#00ff66,#13ff13,#ad27ad,#bd2681,#6512b9,#ff3300de,#5aabde);background-size:400%;width:calc(100% + 5px);height:calc(100% + 5px);z-index:-1;animation:glower 20s linear infinite}@keyframes glower{0%{background-position:0 0}50%{background-position:400% 0}100%{background-position:0 0}}