body {
  text-align: center;
  background-color: gray;
}
.btnAgain {
  width: 100px;
  padding: 10px;
  background-color: azure;
  border: 1px solid black;
}
.number {
  background-color: azure;
  border: 1px solid black;
  font-size: 30px;
  width: 200px;
  display: inline-block;
  padding: 15px;
}
main {
  margin-top: 30px;
  display: flex;
  flex-direction: column;
  gap: 20px;
}
.left {
  text-align: center;
}
input {
  border: 1px solid black;
  padding: 10px;
}
.right {
  text-align: center;
  font-size: 20px;
}
@keyframes zoomInOut {
  0% {
    transform: scale(1);
  }
  50% {
    transform: scale(1.2);
  }
  100% {
    transform: scale(1);
  }
}

.btnAgain.zoom {
animation: zoomInOut 1s ease-in-out 1;
}