body{
  display: flex;
  justify-content: center;
  align-items: center;
  height: 100vh;
}

@keyframes anim {
  0% { 
    transform: rotate(0); 
  }
  100% { 
    transform: rotate(360deg);
  }
}

div{
 animation: anim 3s linear infinite;
 width:50px;
 height:50px;
 line-height: 50px;
 text-align: center;
 font-size: 40px;
 border:2px solid #000;
 border-radius: 50px;
}