SOURCE

<div class="demo_box"></div>

.demo_box{
    width: 100px;
    height: 100px;
    border-radius:50%;
    background:#ffa700;
    clip-path: polygon(0% 100%, 100% 100%, 100% 0%, 0% 0%, 0% 25%, 50% 50%, 0% 80%);
    animation:a 1s infinite alternate;
}
@keyframes a {
    0%, 10% {
        clip-path: polygon(0% 100%, 100% 100%, 100% 0%, 0% 0%, 0% 25%, 50% 50%, 0% 80%)
    }
    90%, 100% {
        clip-path: polygon(0% 100%, 100% 100%, 100% 0%, 0% 0%, 0% 50%, 60% 50%, 0% 60%)
    }
}