main.css

*{
    box-sizing: border-box;
}
body {
	background-color: #000;
	margin: 0px;
	overflow: hidden;
}
#canvas {
    position: fixed;
    left: 0;
    top: 0;
    width: 100%;
    height: 100%;
}
html, body{
    margin: 0;
    padding: 0;
    width: 100vw;
    height: 100vh;
    align-items: center;
    background: #000;
    position: relative;
    font-family: system-ui;
}

*{
    box-sizing: border-box;
}
audio {
    width: 30%;
    bottom: 10px;
    position: fixed;
    left: calc(35%);
    visibility: hidden;
}
audio.active{
    bottom: 10px;
}

#thefile{
    width: 0.1px;
    height: 0.1px;
    opacity: 0;
    overflow: hidden;
    z-index: 1;
    position: absolute;
}

label.file{
    display: inline-block;
    left: 50%;
    top: 50%;
    width: 220px;
    height: 50px;
    border: none;
    outline: none;
    color: #fff;
    background: #111;
    cursor: pointer;
    position: absolute;
    padding: 0.5rem 1.2rem;
    text-align:center;
    font-size: 1.2rem;
    border-radius: 10px;
    
    transform: translate3d(-50%, -50%, 0);
}

label.file:before{
    content: '';
    display:inline-block;
    background: linear-gradient(45deg, #ff0000, #ff7300, #fffb00, #48ff00, #00ffd5, #002bff, #7a00ff, #ff00c8, #ff0000);
    position: absolute;
    top: -2px;
    left:-2px;
    background-size: 400%;
    z-index: -1;
    filter: blur(5px);
    width: calc(100% + 4px);
    height: calc(100% + 4px);
    animation: glowing 20s linear infinite;
    opacity: 0;
    transition: opacity .3s ease-in-out;
    border-radius: 10px;
}


label.file:hover:before{
    opacity: 1;
}

label.file:after{
    z-index: -1;
    content: '';
    position: absolute;
    width: 100%;
    height: 100%;
    background: #111;
    left: 0;
    top: 0;
    border-radius: 10px;
}

@keyframes glowing {
    0% { background-position: 0 0; }
    50% { background-position: 400% 0; }
    100% { background-position: 0 0; }
}

label.file.normal{
    transform: translate3d(10%, 50%, 0);
    padding: 0.8rem 2rem;
    font-size: 1rem;
    text-align: center;
    top: 0;
    left: 0;
}