*, *::before, *::after {
box-sizing: border-box
}

@-webkit-keyframes rotate {
100% {
transform: rotate(1turn)
}
}

@keyframes rotate {
100% {
transform: rotate(1turn)
}
}

.gm {
}

.conic {
position: relative;
z-index: 0;
width: 400px;
height: 300px;
margin: 20px;
border-radius: 10px;
overflow: hidden;
padding: 2rem
}

.conic::before {
content: "";
position: absolute;
z-index: -2;
left: -50%;
top: -50%;
width: 200%;
height: 200%;
background-color: #1a232a;
background-repeat: no-repeat;
background-position: 0 0;
background-image: conic-gradient(transparent,#a8efff,transparent 30%);
-webkit-animation: rotate 4s linear infinite;
animation: rotate 4s linear infinite
}

.conic::after {
content: "";
position: absolute;
z-index: -1;
left: 6px;
top: 6px;
width: calc(100% - 12px);
height: calc(100% - 12px);
background: #000;
border-radius: 5px
}

.conic-demo::after {
-webkit-animation: opacityChange 5s infinite linear;
animation: opacityChange 5s infinite linear
}

@-webkit-keyframes opacityChange {
50% {
opacity: .5
}

100% {
opacity: 1
}
}

@keyframes opacityChange {
50% {
opacity: .5
}

100% {
opacity: 1
}
}