body{
   display: flex;
   justify-content: center;
   align-items: center;
   overflow: hidden;
   margin-top:40vh ;
   background: #161616;
   transform: scale(1.5);
}
.btn{
    font-family: Arial, Helvetica, sans-serif;
    padding: 15px 40px;
    border: none;
    outline: none;
    color: #fff;
    cursor: pointer;
    position: relative;
    z-index: 0;
    border-radius:12px ;
}

.btn::after{
    content: "";
    z-index: -1;
    position: absolute;
    width: 100%;
    height: 100%;
    background-color: #333;
    left: 0;
    top: 0;
    border-radius:10px ;
}
.btn::before{
    content: "";
    background: linear-gradient(
        45deg,
        #FF0000,#FF7300,#FFFB00,#48FF00
        ,#00FFD5,#002BFF,#FF00CB,#FF0000
    );
    position: absolute;
    top: -2px;
    left: -2px;
    background-size: 600%;
    z-index: -1;
    width: calc(100% + 4px);
    height: calc(100% + 4px);
    filter: blur(8px);

    animation: glowing 20s linear infinite;
    transition: opacity .3s ease-in-out;
    border-radius: 10px;
    opacity: 0;
}
@keyframes glowing{
    0% {background-position: 0 0;}
    50% {background-position: 400% 0;}
    100% {background-position: 0 0;}
}

.btn:hover:before{
    opacity: 1;
}
.btn:active::after{
    background: transparent;

}
.btn:active{
    color: #000;
    font-weight: bold;
}