.letter-stage {
  position: fixed;
  inset: 0;
  z-index: 9;
  display: grid;
  place-items: center;
  align-content: center;
  overflow: hidden;
  padding: max(0.45rem, env(safe-area-inset-top)) 0.7rem max(0.45rem, env(safe-area-inset-bottom));
  background: rgba(18, 8, 36, 0.45);
  opacity: 0;
  pointer-events: none;
  transition: opacity 0.6s cubic-bezier(0.4, 0, 0.2, 1);
}
.letter-stage[hidden] { display: none; }
.letter-stage.is-on { opacity: 1; pointer-events: auto; }

.letter-env {
  position: relative;
  width: min(78vw, 17rem);
  height: 11rem;
  border: 0;
  padding: 0;
  background: transparent;
  cursor: pointer;
  filter: drop-shadow(0 18px 28px rgba(12, 4, 26, 0.55));
}
.letter-env__pocket {
  position: absolute;
  inset: 28% 0 0;
  background: linear-gradient(180deg, #f4a9c6, #c45f93);
  border-radius: 0 0 14px 14px;
  box-shadow: inset 0 8px 16px rgba(36, 20, 61, 0.15);
}
.letter-env__flap {
  position: absolute;
  left: 0; right: 0; top: 0;
  height: 58%;
  background: linear-gradient(180deg, #ffd76a, #f4b94e);
  clip-path: polygon(0 0, 100% 0, 50% 100%);
  transform-origin: 50% 0;
  transition: transform 0.7s cubic-bezier(0.05, 0.7, 0.1, 1);
  z-index: 2;
}
.letter-stage.is-open .letter-env__flap { transform: rotateX(-165deg); }
.letter-env__seal {
  position: absolute;
  left: 50%;
  top: 42%;
  z-index: 3;
  width: 2.2rem;
  height: 2.2rem;
  margin: -1.1rem 0 0 -1.1rem;
  border-radius: 50%;
  background: #c41e3a;
  color: #ffd76a;
  display: grid;
  place-items: center;
  font-size: 1.1rem;
  box-shadow: 0 4px 10px rgba(80, 0, 20, 0.4);
  transition: opacity 0.3s, transform 0.3s;
}
.letter-stage.is-open .letter-env__seal { opacity: 0; transform: scale(0.4); }

.letter-sheet {
  position: relative;
  width: min(96vw, 40rem);
  max-height: none;
  overflow: visible;
  padding: 0.75rem 0.95rem 0.85rem;
  border-radius: 6px 6px 12px 12px;
  background:
    linear-gradient(180deg, rgba(255, 248, 232, 0.2), transparent 12%),
    #fff6e8;
  color: #3a2448;
  font: 400 clamp(0.74rem, 2.05vw, 0.92rem)/1.35 "Cormorant Garamond", Georgia, serif;
  box-shadow: 0 24px 50px rgba(12, 4, 26, 0.45);
  transform: translateY(42%) scale(0.92);
  opacity: 0;
  transition: transform 0.85s cubic-bezier(0.05, 0.7, 0.1, 1), opacity 0.5s;
}
.letter-stage.is-open .letter-sheet {
  opacity: 1;
  transform: none;
}
.letter-sheet[hidden] { display: none; }
.letter-stage.is-open .letter-sheet[hidden] { display: block; }
.letter-stage.is-open .letter-env { display: none; }

.letter-dear, .letter-close {
  font-family: "Great Vibes", cursive;
  font-size: clamp(1.2rem, 4vw, 1.55rem);
  color: #c41e3a;
  margin: 0 0 0.4rem;
}
.letter-close { margin-top: 0.45rem; }
.letter-sheet p { margin: 0 0 0.38rem; }
.letter-done { margin-top: 0.35rem; min-height: 44px; padding: 0.55rem 1.1rem; }
.letter-emph {
  font-weight: 600;
  color: #6b2a58;
}
.letter-sign { font-style: italic; opacity: 0.85; margin-bottom: 0; }