*{
  padding: 0;
  margin: 0;
  box-sizing: border-box;
}

body{
  height: 100vh;
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  background-color: #ccc;
}

#emoji{
font-size: 12rem;
filter: grayscale(1);
cursor: pointer;
transition: transform 0.3s,
            filter 0.3s;
}

#emoji:hover{
  transform: scale(1.3);
  filter: grayscale(0);
}