* {
  box-sizing: border-box;
}
body {
  background-color: #111;
  text-align: center;
  height: 100vh;
  width: 100vw;
  display: flex;
  align-items: center;
  justify-content: center;
  overflow: hidden;
  margin: 0;
  padding: 0;
  font-family: 'Arial', sans-serif;
  font-size: 12px;
}
.envelope {
  width: 350px;
  height: 180px;
  background: #b49976;
  position: relative;
}
.envelope__check {
  height: 100%;
  width: 100%;
  z-index: 10;
  opacity: 0;
  position: absolute;
  left: 0;
  top: 0;
  margin: 0;
  cursor: pointer;
}
.envelope__check:checked ~ .envelope__flap {
  transition: transform 0.25s 0s, z-index 0s 0.25s;
  transform: rotateX(-180deg);
  z-index: 0;
}
.envelope__check:checked ~ .envelope__letter {
  transform: translateY(-110%);
  transition: transform 0.25s 0.25s, z-index 0s 0.5s;
  z-index: 5;
}
.envelope__check:checked ~ .envelope__letter .letter__content:nth-child(2),
.envelope__check:checked ~ .envelope__letter .letter__content:nth-child(3) {
  transition: transform 0.25s 0.5s;
  transform: rotateX(0deg);
}
.envelope__flap {
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 75%;
  transition: transform 0.25s 0.5s, z-index 0s 0.5s;
  transform-origin: top center;
  -webkit-backface-visibility: hidden;
          backface-visibility: hidden;
  background: repeating-linear-gradient(-45deg, #c1ab8e, #c1ab8e 10px, #e74c3c 10px, #e74c3c 20px, #c1ab8e 20px, #c1ab8e 30px, #1e90ff 30px, #1e90ff 40px) 0 0/100% 5px no-repeat, #c1ab8e;
  z-index: 4;
  -webkit-clip-path: polygon(5% 40%, 50% 100%, 95% 40%, 100% 0, 0 0);
          clip-path: polygon(5% 40%, 50% 100%, 95% 40%, 100% 0, 0 0);
}
.envelope__flap--inside {
  background: #c1ab8e;
  -webkit-backface-visibility: visible;
          backface-visibility: visible;
}
.envelope__back {
  height: 100%;
  width: 100%;
  height: 100%;
  width: 100%;
  position: absolute;
  top: 0;
  left: 0;
  z-index: 3;
  background: repeating-linear-gradient(-45deg, #cebda6, #cebda6 10px, #e74c3c 10px, #e74c3c 20px, #cebda6 20px, #cebda6 30px, #1e90ff 30px, #1e90ff 40px) 0 100%/100% 5px no-repeat, repeating-linear-gradient(-45deg, #cebda6, #cebda6 10px, #e74c3c 10px, #e74c3c 20px, #cebda6 20px, #cebda6 30px, #1e90ff 30px, #1e90ff 40px) 0 100%/5px 100% no-repeat, repeating-linear-gradient(-45deg, #cebda6, #cebda6 10px, #e74c3c 10px, #e74c3c 20px, #cebda6 20px, #cebda6 30px, #1e90ff 30px, #1e90ff 40px) 100% 100%/5px 100% no-repeat, #cebda6;
  -webkit-clip-path: polygon(80% 40%, 100% 0, 100% 100%, 0 100%, 0 0, 20% 40%);
          clip-path: polygon(80% 40%, 100% 0, 100% 100%, 0 100%, 0 0, 20% 40%);
}
.envelope__back:after {
  height: 100%;
  width: 100%;
  background: repeating-linear-gradient(-45deg, #c7b49a, #c7b49a 10px, #e74c3c 10px, #e74c3c 20px, #c7b49a 20px, #c7b49a 30px, #1e90ff 30px, #1e90ff 40px) 0 100%/100% 5px no-repeat, #c7b49a;
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  -webkit-clip-path: polygon(70% 10%, 100% 100%, 0 100%, 30% 10%);
          clip-path: polygon(70% 10%, 100% 100%, 0 100%, 30% 10%);
}
.envelope__letter {
  height: 90%;
  width: 90%;
  z-index: 1;
  position: absolute;
  left: 5%;
  top: 5%;
  transition: transform 0.25s 0.25s, z-index 0s 0.25s;
  transform: translateY(0);
}
.letter__content {
  height: 100%;
  width: 100%;
  background-color: #fff;
  top: 0;
  left: 0;
  position: absolute;
  padding: 14px;
  text-align: justify;
}
.letter__content:nth-child(2),
.letter__content:nth-child(3) {
  transition: transform 0.25s;
  top: 100%;
  transform-origin: top center;
  transform: rotateX(180deg);
  -webkit-backface-visibility: visible;
          backface-visibility: visible;
  z-index: 2;
  border-top: 1px solid #eee;
}
.letter__content:nth-child(3) {
  -webkit-backface-visibility: hidden;
          backface-visibility: hidden;
}
.sign-off {
  position: absolute;
  bottom: 12px;
  right: 12px;
  font-size: 20px;
  font-family: cursive;
  transform: skewX(-20deg);
}