:root {
  --paper: #efe5d5;
  --paper-light: #fbf6ed;
  --paper-mid: #e4d5c1;
  --paper-dark: #c9b79f;
  --shadow: rgba(30, 20, 10, 0.28);
}

* { box-sizing: border-box; }

body {
  margin: 0;
  background: #f4f4f4;
  font-family: Arial, Helvetica, sans-serif;
}

/* Replace this demo wrapper with your site's existing content column. */
.demo-column {
  width: min(100%, 860px);
  margin: 0 auto;
  padding: 24px 12px;
}

.mail-reveal {
  position: relative;
  width: 100%;
  aspect-ratio: 1 / 1.78;
  overflow: hidden;
  perspective: 1400px;
  isolation: isolate;
}

.poster {
  position: absolute;
  z-index: 3;
  left: 4%;
  bottom: 19%;
  width: 92%;
  height: auto;
  display: block;
  transform-origin: 50% 100%;
  transform: translateY(81%) rotateX(0deg) rotateZ(0deg) scale(0.985);
  filter: drop-shadow(0 18px 18px rgba(0, 0, 0, 0.22));
  will-change: transform;
}

.envelope-back {
  position: absolute;
  z-index: 1;
  left: 0;
  right: 0;
  bottom: 0;
  height: 24%;
  border: 1px solid rgba(92, 68, 42, 0.3);
  border-radius: 3px 3px 12px 12px;
  background:
    radial-gradient(circle at 18% 20%, rgba(255,255,255,.55), transparent 24%),
    repeating-linear-gradient(105deg, rgba(90,65,35,.025) 0 1px, transparent 1px 5px),
    linear-gradient(160deg, var(--paper-light), var(--paper-mid));
  box-shadow: 0 18px 28px var(--shadow);
}

.envelope-flap {
  position: absolute;
  z-index: 5;
  left: 0;
  right: 0;
  bottom: 12.1%;
  height: 12.5%;
  clip-path: polygon(0 0, 50% 100%, 100% 0);
  transform-origin: 50% 0;
  transform: rotateX(0deg);
  background:
    repeating-linear-gradient(105deg, rgba(90,65,35,.025) 0 1px, transparent 1px 5px),
    linear-gradient(180deg, #f8f0e4 0%, #dbcbb6 100%);
  border-top: 1px solid rgba(92, 68, 42, 0.32);
  filter: drop-shadow(0 7px 5px rgba(40, 25, 12, .22));
  backface-visibility: visible;
  will-change: transform;
}

.envelope-front {
  position: absolute;
  z-index: 4;
  left: 0;
  right: 0;
  bottom: 0;
  height: 18.5%;
  overflow: hidden;
  border: 1px solid rgba(92, 68, 42, 0.28);
  border-radius: 2px 2px 12px 12px;
  background:
    radial-gradient(circle at 75% 72%, rgba(255,255,255,.35), transparent 30%),
    repeating-linear-gradient(105deg, rgba(90,65,35,.022) 0 1px, transparent 1px 5px),
    linear-gradient(160deg, var(--paper-light), var(--paper-mid));
  box-shadow: inset 0 1px rgba(255,255,255,.8);
}

.envelope-front::before,
.envelope-front::after {
  content: "";
  position: absolute;
  bottom: -38%;
  width: 72%;
  height: 145%;
  background: linear-gradient(145deg, rgba(255,255,255,.42), rgba(203,184,159,.2));
}

.envelope-front::before {
  left: -34%;
  transform: rotate(37deg);
  border-right: 1px solid rgba(92,68,42,.22);
}

.envelope-front::after {
  right: -34%;
  transform: rotate(-37deg);
  border-left: 1px solid rgba(92,68,42,.22);
}

.crease {
  position: absolute;
  z-index: 2;
  bottom: 2%;
  width: 54%;
  height: 1px;
  background: rgba(102, 77, 49, .2);
}

.crease-left { left: 0; transform: rotate(29deg); transform-origin: left; }
.crease-right { right: 0; transform: rotate(-29deg); transform-origin: right; }

.paper-highlight {
  position: absolute;
  z-index: 3;
  inset: 5% 4% auto 4%;
  height: 1px;
  background: rgba(255,255,255,.7);
}

/* Animation begins after JavaScript adds .is-opening at page load. */
.mail-reveal.is-opening .envelope-flap {
  animation: open-flap 0.36s cubic-bezier(.3,.05,.2,1) forwards;
}

.mail-reveal.is-opening .poster {
  animation: lift-poster 0.78s 0.22s cubic-bezier(.18,.8,.22,1) forwards;
}

@keyframes open-flap {
  0%   { transform: rotateX(0deg); z-index: 5; }
  52%  { transform: rotateX(96deg); z-index: 2; }
  100% { transform: rotateX(178deg); z-index: 2; }
}

@keyframes lift-poster {
  0%   { transform: translateY(81%) rotateX(0deg) rotateZ(0deg) scale(.985); }
  64%  { transform: translateY(-1.5%) rotateX(-7deg) rotateZ(-.45deg) scale(1.004); }
  100% { transform: translateY(0) rotateX(-3deg) rotateZ(0deg) scale(1); }
}

@media (prefers-reduced-motion: reduce) {
  .poster { transform: none; }
  .envelope-flap { transform: rotateX(178deg); z-index: 2; }
  .mail-reveal.is-opening .poster,
  .mail-reveal.is-opening .envelope-flap { animation: none; }
}