.container {
  width: 100%;
  min-height: 100%;
  min-height: 100vh;
  min-height: 100dvh;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  box-sizing: border-box;
  padding: max(8px, env(safe-area-inset-top, 0px))
    max(8px, env(safe-area-inset-right, 0px))
    max(8px, env(safe-area-inset-bottom, 0px))
    max(8px, env(safe-area-inset-left, 0px));
}

.envelope-wrapper {
  position: relative;
  display: inline-block;
  max-width: 100%;
  margin: 0;
  flex-shrink: 0;
  vertical-align: middle;
  text-decoration: none;
  color: inherit;
}

.envelope {
  position: relative;
  display: block;
  width: 300px;
  height: 200px;
  margin: 0;
  background-color: #c9d0d2;
  overflow: visible;
}

.envelope .envelope__card {
  position: absolute;
  bottom: 0;
  left: 0;
  right: 0;
  width: auto;
  min-height: 200px;
  height: auto;
  margin: 0;
  box-sizing: border-box;
  overflow: visible;
  transform-style: preserve-3d;
  background: linear-gradient(168deg, #fffefb 0%, #faf3e8 42%, #f3e8dc 100%);
  border: 1px solid rgba(201, 162, 79, 0.45);
  box-shadow:
    0 6px 28px rgba(74, 28, 42, 0.18),
    0 0 0 1px rgba(255, 255, 255, 0.45) inset,
    0 1px 0 rgba(255, 255, 255, 0.65) inset;
}

/* Khung 3D + chiều cao động: khi đóng chỉ hở một dải giấy gấp */
.envelope .letter-scene {
  perspective: 1100px;
  perspective-origin: 50% 0%;
  transform-style: preserve-3d;
  overflow: hidden;
  max-height: 3.25rem;
  transition: max-height 0.05s;
}

.envelope .envelope__card.open .letter-scene {
  max-height: min(92vh, 3200px);
  overflow-x: hidden;
  overflow-y: auto;
  -webkit-overflow-scrolling: touch;
  overscroll-behavior-y: contain;
  transition: max-height 1.15s cubic-bezier(0.33, 0.9, 0.32, 1) 0.45s;
}

.envelope .letter {
  position: relative;
  padding: 1.1rem 1.15rem 1.15rem;
  box-sizing: border-box;
  display: flex;
  flex-direction: column;
  gap: 0.45rem;
  font-family: "Pacifico", cursive, sans-serif;
  color: #3a2a2c;
  transform-origin: top center;
  backface-visibility: hidden;
  -webkit-backface-visibility: hidden;
  background-image:
    radial-gradient(
      ellipse 100% 55% at 50% 0%,
      rgba(255, 252, 248, 0.95),
      transparent 62%
    ),
    repeating-linear-gradient(
      0deg,
      transparent,
      transparent 1.14rem,
      rgba(139, 90, 98, 0.045) 1.14rem,
      rgba(139, 90, 98, 0.045) calc(1.14rem + 1px)
    );
}

.envelope .letter::before {
  content: "";
  position: absolute;
  inset: 0.55rem;
  border: 1px solid rgba(183, 110, 121, 0.28);
  border-radius: 1px;
  box-shadow: 0 0 0 1px rgba(255, 255, 255, 0.35) inset;
  pointer-events: none;
  z-index: 0;
}

.envelope .letter > * {
  position: relative;
  z-index: 1;
}

/* Trạng thái gấp: xoay theo trục X + nén theo Y, mờ nhẹ */
.envelope .envelope__card:not(.open) .letter {
  transform: rotateX(76deg) scaleY(0.2);
  opacity: 0.58;
}

/* Khi mở: giữ khung hình 0% trong lúc delay (animation-fill-mode: both) */
.envelope .envelope__card.open .letter {
  -webkit-animation: letterUnfold 1.05s cubic-bezier(0.25, 0.85, 0.35, 1) 0.52s
    both forwards;
  animation: letterUnfold 1.05s cubic-bezier(0.25, 0.85, 0.35, 1) 0.52s both
    forwards;
}

@keyframes letterUnfold {
  0% {
    transform: rotateX(76deg) scaleY(0.2);
    opacity: 0.58;
  }
  35% {
    opacity: 0.82;
    transform: rotateX(38deg) scaleY(0.62);
  }
  68% {
    opacity: 0.96;
    transform: rotateX(8deg) scaleY(0.96);
  }
  100% {
    transform: rotateX(0deg) scaleY(1);
    opacity: 1;
  }
}

@-webkit-keyframes letterUnfold {
  0% {
    -webkit-transform: rotateX(76deg) scaleY(0.2);
    opacity: 0.58;
  }
  35% {
    opacity: 0.82;
    -webkit-transform: rotateX(38deg) scaleY(0.62);
  }
  68% {
    opacity: 0.96;
    -webkit-transform: rotateX(8deg) scaleY(0.96);
  }
  100% {
    -webkit-transform: rotateX(0deg) scaleY(1);
    opacity: 1;
  }
}

.envelope .letter__title:empty::after {
  display: none;
}

.envelope .letter__title {
  margin: 0;
  padding-bottom: 0.15rem;
  font-size: 1.65rem;
  font-weight: 600;
  line-height: 1.2;
  text-align: center;
  letter-spacing: 0.04em;
  color: #6b2a3d;
  text-shadow:
    0 1px 0 rgba(255, 255, 255, 0.8),
    0 0 40px rgba(255, 220, 200, 0.5);
}

.envelope .letter__title::after {
  content: "✦";
  display: block;
  margin-top: 0.4rem;
  font-size: 0.55rem;
  letter-spacing: 0.65em;
  color: #b8860b;
  opacity: 0.88;
  text-shadow: none;
}

.envelope .letter__body {
  margin: 0;
}

.envelope .letter__paragraph {
  margin: 0 0 0.28em;
  padding: 0;
  font-size: 0.84rem;
  line-height: 1.34;
  white-space: pre-wrap;
  word-break: break-word;
  color: #4a3538;
  text-indent: 1.2em;
}

.envelope .letter__paragraph:last-child {
  margin-bottom: 0;
}

/* Đoạn đầu: chữ cái lớn, không thụt (tránh chồng với drop cap) */
.envelope .letter__paragraph:first-of-type {
  text-indent: 0;
}

.envelope .letter__paragraph:first-of-type::first-letter {
  float: left;
  margin: 0.06em 0.1em 0 0;
  padding-right: 0.02em;
  font-size: 2.2em;
  font-weight: 600;
  line-height: 0.88;
  color: #8b3d52;
  text-shadow: 0 1px 0 rgba(255, 255, 255, 0.6);
}

.envelope .letter__signature {
  margin: 0.35rem 0 0;
  padding-top: 0.65rem;
  border-top: 1px solid rgba(183, 110, 121, 0.22);
  font-size: 1.05rem;
  font-weight: 500;
  font-style: italic;
  text-align: right;
  color: #7a3d4f;
  letter-spacing: 0.02em;
  opacity: 0.95;
}

/* Icon bánh cuối thư — hào quang hồng + bấm sang imageFly */
.envelope .letter__cake-wrap {
  display: flex;
  justify-content: center;
  align-items: center;
  margin: 0.85rem 0 0;
  padding: 0.55rem 0 0.2rem;
  position: relative;
}

.envelope.open .letter__cake-wrap {
  cursor: pointer;
}

.envelope.open .letter__cake-wrap:focus-visible {
  outline: 2px solid rgba(255, 105, 180, 0.75);
  outline-offset: 4px;
  border-radius: 12px;
}

.envelope .letter__cake-wrap::before {
  content: "";
  position: absolute;
  width: 4.75rem;
  height: 4.75rem;
  border-radius: 50%;
  background: radial-gradient(
    circle,
    rgba(255, 143, 171, 0.5) 0%,
    rgba(255, 105, 180, 0.22) 42%,
    transparent 68%
  );
  animation: letterCakeAura 2.4s ease-in-out infinite;
  pointer-events: none;
}

@keyframes letterCakeAura {
  0%,
  100% {
    transform: scale(0.9);
    opacity: 0.72;
  }
  50% {
    transform: scale(1.12);
    opacity: 1;
  }
}

.envelope .letter__cake-icon {
  position: relative;
  z-index: 1;
  width: 3.25rem;
  height: auto;
  max-width: 100%;
  display: block;
  object-fit: contain;
  animation: letterCakeGlow 2s ease-in-out infinite alternate;
}

@keyframes letterCakeGlow {
  0% {
    filter: drop-shadow(0 0 4px rgba(255, 182, 193, 0.95))
      drop-shadow(0 0 12px rgba(255, 105, 180, 0.5));
    transform: scale(1);
  }
  100% {
    filter: drop-shadow(0 0 10px rgba(255, 192, 203, 1))
      drop-shadow(0 0 22px rgba(255, 20, 147, 0.55))
      drop-shadow(0 0 34px rgba(255, 105, 180, 0.35));
    transform: scale(1.05);
  }
}

.envelope .envelope__card.open {
  -webkit-animation: cardJump 0.5s ease 0.5s forwards;
  -o-animation: cardJump 0.5s ease 0.5s forwards;
  animation: cardJump 0.5s ease 0.5s forwards;
  z-index: 1;
}

.envelope .envelope__side {
  position: absolute;
  top: 0;
  width: 0;
  height: 0;
  border-style: solid;
  z-index: 2;
}

.envelope .envelope__side--left {
  left: 0;
  border-width: 100px 0 100px 150px;
  border-color: transparent transparent transparent #ffffff;
}

.envelope .envelope__side--right {
  right: 0;
  border-width: 100px 150px 100px 0;
  border-color: transparent #ffffff transparent transparent;
}

.envelope .envelope__side--bottom {
  top: auto;
  left: 0;
  bottom: 0;
  border-width: 0 150px 100px 150px;
  border-color: transparent transparent #ecf0f1 transparent;
}

.envelope .envelope__side--top {
  top: 0;
  left: 0;
  bottom: auto;
  border-width: 100px 150px 0 150px;
  border-color: #ecf0f1 transparent transparent transparent;
  z-index: 1;
}

.envelope.open > .envelope__side--top {
  top: -100px;
  border-width: 0 150px 100px 150px;
  border-color: transparent transparent #c9d0d2 transparent;
}

.heart {
  position: relative;
  top: 50%;
  left: 50%;
  margin-top: -25%;
  margin-left: -25px;
  width: 50px;
  fill: url(#heartRomanticGrad);
  z-index: 2;
}

.heart use {
  fill: url(#heartRomanticGrad);
}

.envelope:hover .heart {
  transform: scale(1.2);
  transition: 0.5s ease;
}

.envelope.open:hover .heart {
  transform: none;
}

/* Sau khi thư được kéo ra: ẩn phần bao (nền xám + nắp + tim), giữ thư hiển thị */
@keyframes envelopeBgFadeOut {
  to {
    background-color: transparent;
  }
}

@keyframes envelopeShellFadeOut {
  to {
    opacity: 0;
    visibility: hidden;
  }
}

.envelope.open {
  animation: envelopeBgFadeOut 0.45s ease 0.95s forwards;
}

.envelope.open > .envelope__side,
.envelope.open > .heart {
  animation: envelopeShellFadeOut 0.45s ease 0.95s forwards;
}

/* Căn giữa toàn bộ khối do .container flex — không dịch margin khi mở */
.envelope-wrapper.letter-revealed,
.envelope-wrapper.letter-revealed-done {
  margin: 0;
}

/* Giữ thẻ ở vị trí đã kéo ra (không để cardJump “hồi sinh” giữa các bước) */
.envelope-wrapper.letter-revealed:not(.letter-revealed-settling):not(
    .letter-revealed-done
  )
  .envelope.open
  > .envelope__card.open {
  -webkit-animation: none;
  animation: none;
  -webkit-transform: translate3d(0, -100%, 0);
  transform: translate3d(0, -100%, 0);
}

/* Bước 2a — lá thư trượt xuống (translate3d + easing mềm ở đoạn cuối) */
@-webkit-keyframes letterFall {
  0% {
    -webkit-transform: translate3d(0, -100%, 0);
  }
  100% {
    -webkit-transform: translate3d(0, 0, 0);
  }
}

@keyframes letterFall {
  0% {
    transform: translate3d(0, -100%, 0);
  }
  100% {
    transform: translate3d(0, 0, 0);
  }
}

.envelope-wrapper.letter-revealed.letter-revealed-settling
  .envelope.open
  > .envelope__card.open {
  -webkit-animation: letterFall 1.12s cubic-bezier(0.18, 0.82, 0.22, 1) forwards;
  animation: letterFall 1.12s cubic-bezier(0.18, 0.82, 0.22, 1) forwards;
  will-change: transform;
  -webkit-backface-visibility: hidden;
  backface-visibility: hidden;
}

/* Bước 2b — sau khi rơi xong: chuyển sang bố cục dòng chảy bình thường */
.envelope-wrapper.letter-revealed-done .envelope.open {
  height: auto;
  min-height: 0;
}

.envelope-wrapper.letter-revealed-done .envelope.open > .envelope__card.open {
  position: relative;
  left: auto;
  right: auto;
  bottom: auto;
  width: 100%;
  max-width: 100%;
  margin-left: 0;
  margin-right: 0;
  box-sizing: border-box;
  -webkit-animation: none;
  animation: none;
  -webkit-transform: none;
  transform: none;
  will-change: auto;
}

@keyframes cardJump {
  from {
    transform: translateY(0);
  }
  to {
    transform: translateY(-100%);
  }
}

@-webkit-keyframes cardJump {
  from {
    -webkit-transform: translateY(0);
  }
  to {
    -webkit-transform: translateY(-100%);
  }
}

/* Màn rộng (máy tính): bao + lá thư ~1,4× so với mobile */
@media (min-width: 900px) {
  .envelope {
    width: 420px;
    height: 280px;
  }

  .envelope .envelope__card {
    left: 0;
    right: 0;
    min-height: 280px;
  }

  .envelope .letter-scene {
    max-height: 3.6rem;
  }

  .envelope .envelope__side--left {
    border-width: 140px 0 140px 210px;
  }

  .envelope .envelope__side--right {
    border-width: 140px 210px 140px 0;
  }

  .envelope .envelope__side--bottom {
    border-width: 0 210px 140px 210px;
  }

  .envelope .envelope__side--top {
    border-width: 140px 210px 0 210px;
  }

  .envelope.open > .envelope__side--top {
    top: -140px;
    border-width: 0 210px 140px 210px;
  }

  .heart {
    margin-left: -35px;
    width: 70px;
    top: 54%;
    margin-top: -22%;
  }

  .envelope .letter {
    padding: 1.35rem 1.45rem 1.4rem;
    gap: 0.55rem;
  }

  .envelope .letter::before {
    inset: 0.65rem;
  }

  .envelope .letter__title {
    font-size: 2.05rem;
  }

  .envelope .letter__paragraph {
    font-size: 1.12rem;
    line-height: 1.4;
    text-indent: 1.15em;
  }

  .envelope .letter__paragraph:first-of-type {
    text-indent: 0;
  }

  .envelope .letter__paragraph:first-of-type::first-letter {
    font-size: 2.35em;
  }

  .envelope .letter__signature {
    font-size: 1.32rem;
  }

  .envelope .letter__cake-icon {
    width: 3.75rem;
  }

  .envelope .letter__cake-wrap::before {
    width: 5.5rem;
    height: 5.5rem;
  }

  /* Máy tính: cuộn được nhưng ẩn thanh trượt */
  .envelope .envelope__card.open .letter-scene {
    scrollbar-width: none;
    -ms-overflow-style: none;
  }

  .envelope .envelope__card.open .letter-scene::-webkit-scrollbar {
    display: none;
  }
}

/* Màn thấp (điện thoại ngang, cửa sổ thấp): tránh thư bị đẩy/cắt — cuộn trong khung thư */
@media (max-height: 600px) {
  .envelope .envelope__card.open .letter-scene {
    max-height: calc(100vh - 28px);
    overflow-x: hidden;
    overflow-y: auto;
    -webkit-overflow-scrolling: touch;
    overscroll-behavior-y: contain;
    scrollbar-width: none;
    -ms-overflow-style: none;
  }

  .envelope .envelope__card.open .letter-scene::-webkit-scrollbar {
    display: none;
  }

  .container {
    justify-content: center;
    align-items: center;
    overflow-y: auto;
    -webkit-overflow-scrolling: touch;
  }

  .envelope-wrapper,
  .envelope-wrapper.letter-revealed,
  .envelope-wrapper.letter-revealed-done {
    margin: 0;
  }
}

@supports (height: 100dvh) {
  @media (max-height: 600px) {
    .envelope .envelope__card.open .letter-scene {
      max-height: calc(100dvh - 28px);
    }
  }
}