#envelope {
  background: #b6a175;
   width: 300px;
   height: 200px;
   position: absolute;
   left: 50%;
   top: 50%; 
   margin-left: -150px;
   margin-top: -50px;
  border-bottom-left-radius: 20px;
  border-bottom-right-radius: 20px;
  box-shadow: 10px 10px 10px rgba(0,0,0,0.5);
}

#lid {
  position: relative;
  top: -150px;
  width: 0px;
  height: 0px;
  border-style: solid;
  border-width: 0 150px 150px 150px;
  border-color: transparent transparent #b6a175 transparent;
  
}

#letter {
  position: relative;
  background: #fff;
  top: -150px;
  width: 280px;
  height: 200px;
  left: 10px;
  top: -220px;
  animation: out 5s infinite linear;
  box-shadow: 2px 2px 5px rgba(0,0,0,0.5);
}

#left-corner {
  position: relative;
  top: -315px;
  left: 10px;
  width: 0px;
  height: 0px;
  border-style: solid;
  border-width: 150px 0 0 250px;
  border-color: transparent transparent transparent #b6a175;

}

#right-corner {
  position: relative;
  top: -470px;
  left: 50px;
  width: 0px;
height: 0px;
border-style: solid;
border-width: 0 0 150px 250px;
border-color: transparent transparent #b6a175 transparent;
}

@keyframes out {
	0% {top: -220px;}
  25% {top: -200px;}
  50% {top: -220px;}
  75% {top: -200px;}
}