body 
{
    margin: 0;
    display: flex;
    align-items: center;
    justify-content: center;
    height: 100vh;
    background-color: #212121;
}
   
.pulse 
{
     width: 100px;
     height: 100px;
     background-color: #58ea00;
     color: white;
     border-radius: 50%;
     text-align: center;
     line-height: 100px;
     font-size: 48px;
     position: relative;
}
   
.pulse:before, .pulse:after 
{
     content: '';
     position: absolute;
     left: -20px;
     right: -20px;
     top: -20px;
     bottom: -20px;
     border: 1px solid #58ea00;
     border-radius: 50%;
     animation: pulse 1.5s linear infinite;
}
   
.pulse:after
{
     animation-delay: 0.5s;
}
   
@keyframes pulse 
{
     0% { transform: scale(0.5); opacity: 0 }
     50% { transform: scale(1); opacity: 1 }
     100% { transform: scale(1.2); opacity: 0 }
}