thank.css

body{
  overflow-x: hidden;
  padding: 0;
  margin: 0;
}
.thankyouCard{
  align-items: center;
  padding: 200px 500px 10px 500px;
  background-image: url('https://images.pexels.com/photos/3445727/pexels-photo-3445727.jpeg?auto=compress&cs=tinysrgb&dpr=1&w=500');
  background-position: center;
  background-size: cover;
  background-repeat: no-repeat;
}

@media(max-width:1135px)
{
  .thankyouCard{
           padding: 260px 360px;
  }
}

@media(max-width:843px)
{
  .thankyouCard{
           padding: 260px 260px;
  }
}
@media(max-width:646px)
{
  .thankyouCard{
           padding: 260px 100px;
  }
}


.container-2{
    height: 100%;
    width: 400px;
    margin: 30px;
    padding: 30px;
  }

.card3{ 
    transform: translate(-30%,-20%);
  }
  
  .envelope{
    position: relative;
    width: 400px;
    height: 300px;
    background-color: crimson;
    box-shadow: 0 5px 10px 3px #000;
  
  }
  
  .envelope::before{
    position: absolute;
    content: "";
    top: 0px;
    left: 0px;
    border-right: 200px solid transparent;
    border-left: 200px solid transparent;
    border-top: 150px solid  crimson;
    border-bottom: 150px solid  transparent;
    transform-origin: top;
    transform: rotateX(0deg);
    z-index: 9;
  }
  
  .envelope::after{
    position: absolute;
    content: "";
    top: 0px;
    left: 0px;
    border-right: 200px solid crimson;
    border-left: 200px solid  crimson;
    border-top: 150px solid transparent;
    border-bottom: 150px solid  crimson;
    z-index: 99;
  }

  .envelope>h3{
    z-index: 20;
    opacity: 2;
  }
  
  .letter{
    position: absolute;
    top: 0px;
    left: 0px;
    background-image: url(https://images.pexels.com/photos/1111322/pexels-photo-1111322.jpeg?auto=compress&cs=tinysrgb&dpr=1&w=500); 
    opacity: 0.8;
    width: 400px;
    height: 300px;
    border-radius: 22px;
    transition: .8s ease;
    z-index: 8;
  
  }
  
  .card3>.letter>h3 {
    opacity: 1;
    color: white;
    text-align: center;
  }

  .card3>.letter>p{
    opacity: 1;
    color: white;
    text-align: center;
    font-weight: 500;
    padding: 0px 35px;
    
  }
  
  .para{
    margin-top: -12px;
    margin-left: 25px;
    margin-right: 20px;
  }
  
  .card3:hover .envelope::before{
    transform: rotateX(180deg);
    transition: 1s ease;
   
  }
  
  .card3:hover .letter{
    top: -120px;
    transition: 1s ease;
    z-index: 10;
  }