.envelope-container {
  position: relative;
  width: 80%;
  margin: 50px auto;
  perspective: 1000px;
}

.envelope {
  width: 100%;
  transition: transform 5s ease;
  transform-style: preserve-3d;
}

.envelope-container:hover .envelope {
  transform: rotateX(180deg);
}

.flap {
  transform-origin: top center;
  transition: transform 1s ease;
}

.envelope-container:hover .flap {
  transform: rotateX(-180deg);
}

.rsvp-card {
  position: absolute;
  top: 50px;
  left: 20px;
  width: 260px;
  height: 80px;
  background: #fff;
  border: 2px solid #333;
  padding: 10px;
  box-sizing: border-box;
  opacity: 0;
  transform: translateY(20px);
  transition: opacity 1s ease, transform 1s ease;
}

.envelope-container:hover .rsvp-card {
  opacity: 1;
  transform: translateY(0);
}