.box{box-shadow:0px;background:linear-gradient(#ffffff40,#ffffff40)padding-box,linear-gradient(var(--angle),#fff,#ffffff40,#ffffff40)border-box;border:2px solid #0000;justify-content:center;align-items:center;transition:all .3s;animation:3s linear infinite rotate;display:flex}@property --angle{syntax:"<angle>";inherits:false;initial-value:0deg}@keyframes rotate{to{--angle:180deg}to{--angle:360deg}}