Градиентный border

.gradien-border {
border: 1px solid #fff!important;
border-image: linear-gradient(135deg, rgb(255 255 255 / 35%) ,rgb(255 255 255 / 0%))!important;
-moz-border-image: -moz-linear-gradient(135deg, rgb(255 255 255 / 35%) ,rgb(255 255 255 / 0%))!important;
-webkit-border-image: -webkit-linear-gradient(135deg, rgb(255 255 255 / 35%) ,rgb(255 255 255 / 0%))!important;
border-image-slice: 1!important;
border-radius:16px;
}