* {
  margin: 0;
  padding: 0;
}
.container {
  background: #f0f0f0;
  box-sizing: border-box;
  display: flex;
  justify-content: center;
  align-items: center;
  width: 100vw;
  height: 100vh;
}
.box {
  border-radius: 20px;
  width: 60px;
  height: 60px;
  background: #f0f0f0;
  box-shadow: 0 0 0 #cccccc, 0 0 0 #ffffff, 10px 10px 10px #cccccc inset,
    -10px -10px 10px #ffffff inset;
  animation: anime 3s cubic-bezier(0.16, 1, 0.3, 1) 1s infinite alternate;
  /* animation-fill-mode: forwards; */
}

@keyframes anime {
  0% {
    width: 60px;
    height: 60px;
    background: #f0f0f0;
    box-shadow: 0 0 0 #cccccc, 0 0 0 #ffffff, 10px 10px 10px #cccccc inset,
      -10px -10px 10px #ffffff inset;
  }
  25% {
    width: 60px;
    height: 60px;
    background: #f8f8f8;
    box-shadow: 10px 10px 10px #cccccc, 10px 10px 10px #ffffff, 0 0 0 #cccccc inset,
      0 0 0 #ffffff inset;
  }
  50% {
    width: 60px;
    height: 240px;
    background: #f8f8f8;
    box-shadow: 10px 10px 10px #cccccc, 10px 10px 10px #ffffff, 0 0 0 #cccccc inset,
      0 0 0 #ffffff inset;
  }
  100% {
    width: 480px;
    height: 240px;
    background: #fafafa;
    box-shadow: 40px 40px 40px #cccccc, 0 0 0 #ffffff, 0 0 0 #cccccc inset,
      2px 2px 2px #ffffff inset;
  }
}