body{
  position: relative;
  display: flex;
  justify-content: center;
  align-items: center;
  height: 100vh;
}
.square{
  width: 150px;
    height: 150px;
    border-radius: 12px;
    background-color: grey;
    
    display: flex;
    justify-content: center;
    align-items: center;
    
    
    transition: .3s;
  }
  .square span{
    color: green;
    font-size: 20px;
    transition: .3s;
    opacity: 0;
  }
  .square:hover span{
    opacity: 1;
  }
  
.block{
  position: absolute;
    top: 300px;
    height: 25px;
    
  transform: scaleX(0);
  transform-origin: left;

}
.white{
    background-color: red;
}

.square:hover .block{
  width: 50%;
  transform: scaleX(1);
}

.block{
  transition-duration: .3s;
  
}
.white{
   transition-timing-function: ease;
   
}