:root {
  --bg: #fde4ec;
  --bg-deep: #f8cfdc;
  --paper: #fffdf8;
  --ink: #633441;
  --muted: #9d6877;
  --envelope: #f5efe2;
  --envelope-edge: #d8c9b0;
  --seal: #c9224e;
  --rose: #c9224e;
  --rose-soft: #f7b7c8;
  --shadow: 0 24px 60px rgba(133, 55, 78, 0.18);
  --scene-position: center;
  --scene-size: cover;
}

@font-face {
  font-family: "Aa Suibi Hand";
  src: url("./assets/fonts/aa-suibi-hand.ttf") format("truetype");
  font-weight: 400;
  font-display: swap;
}

@font-face {
  font-family: "Fangzheng Jinghong";
  src: local("方正字迹-惊鸿体 简");
  font-weight: 500;
  font-display: swap;
}

@font-face {
  font-family: "Zihun Shoujin";
  src: url("./assets/fonts/zihun-shoujin.ttf") format("truetype");
  font-weight: 400;
  font-display: swap;
}

* {
  box-sizing: border-box;
}

html,
body {
  margin: 0;
  width: 100%;
  height: 100%;
  overflow: hidden;
}

body {
  font-family:
    "华文行楷",
    "STXingkai",
    "Aa Suibi Hand",
    "STSong",
    "SimSun",
    serif;
  color: var(--ink);
  background:
    url("./assets/french-toast-bg-v2.png") var(--scene-position) / var(--scene-size) no-repeat fixed,
    #f8d9e3;
}

.page {
  position: relative;
  width: 100%;
  height: 100dvh;
  padding: 18px;
  display: grid;
  place-items: center;
  overflow: hidden;
}

.page::before {
  content: "";
  position: absolute;
  inset: 0;
  z-index: 0;
  display: block;
  background: url("./素材/底纹.png") center / cover no-repeat;
  opacity: 0.38;
  mix-blend-mode: multiply;
  pointer-events: none;
}

.page::after {
  content: "";
  position: absolute;
  inset: 0;
  z-index: 0;
  display: block;
  background: url("./assets/浮板.png") var(--scene-position) / var(--scene-size) no-repeat;
  pointer-events: none;
}

.intro {
  position: relative;
  z-index: 2;
  grid-area: 1 / 1;
  display: grid;
  justify-items: center;
  transition:
    opacity 0.55s ease,
    transform 0.55s ease;
}

.music-button {
  position: absolute;
  z-index: 5;
  top: max(30px, calc((100dvh - min(88dvh, 760px)) / 2 + 16px));
  right: max(22px, calc((100vw - min(76vw, 560px)) / 2 + 18px));
  width: 54px;
  height: 54px;
  display: grid;
  place-items: center;
  border: 0;
  padding: 0;
  background: transparent;
  cursor: pointer;
  -webkit-tap-highlight-color: transparent;
}

.music-icon {
  width: 100%;
  height: 100%;
  object-fit: contain;
  opacity: 0.6;
  filter: drop-shadow(0 5px 8px rgba(71, 31, 43, 0.18));
  mix-blend-mode: multiply;
}

.music-button.is-playing .music-icon {
  animation: musicSpin 9s linear infinite;
}

.music-muted {
  position: absolute;
  inset: 8px;
  display: none;
  place-items: center;
  color: #9a4a61;
  opacity: 0.55;
  font-size: 0;
  border: 2px solid currentColor;
  border-radius: 50%;
}

.music-button.is-paused .music-muted {
  display: grid;
}

.music-muted::after {
  content: "";
  width: 2px;
  height: 120%;
  background: currentColor;
  border-radius: 999px;
  transform: rotate(45deg);
}

.envelope-button {
  display: grid;
  justify-items: center;
  gap: 6px;
  border: 0;
  padding: 20px;
  color: var(--ink);
  background: transparent;
  cursor: pointer;
  transform: translateY(calc(-9vh + 20px));
  -webkit-tap-highlight-color: transparent;
}

.envelope-button:focus-visible {
  outline: 3px solid rgba(106, 137, 96, 0.5);
  outline-offset: 10px;
  border-radius: 18px;
}

.envelope {
  position: relative;
  width: min(92vw, 581px);
  aspect-ratio: 1.2;
  filter: drop-shadow(var(--shadow));
  transform: translateY(-10vh) rotate(-5deg);
  transition: transform 0.35s ease;
}

.envelope-button:hover .envelope {
  transform: translateY(calc(-10vh - 8px)) rotate(-5deg);
}

.envelope-back,
.envelope-front,
.envelope-flap,
.letter-peek,
.paper-pop,
.envelope-art {
  position: absolute;
  inset: 0;
}

.envelope-art {
  z-index: 4;
  width: 100%;
  height: 100%;
  object-fit: contain;
  object-position: center;
  pointer-events: none;
}

.envelope-back {
  display: none;
  z-index: 1;
  background: var(--envelope);
  border: 1px solid var(--envelope-edge);
  border-radius: 10px;
}

.letter-peek {
  z-index: 2;
  width: 72%;
  height: 72%;
  left: 14%;
  top: 8%;
  background:
    linear-gradient(105deg, rgba(255, 255, 255, 0.36), transparent 34%),
    linear-gradient(255deg, rgba(215, 203, 182, 0.2), transparent 38%),
    linear-gradient(#ffffff 0 0) padding-box,
    repeating-linear-gradient(
      to bottom,
      transparent 0 24px,
      rgba(159, 185, 149, 0.22) 24px 25px
    );
  border: 1px solid rgba(216, 201, 176, 0.78);
  border-radius: 18px 10px 16px 9px;
  transform: translateY(32px) scaleX(0.62) scaleY(0.36) rotate(-7deg);
  transform-origin: center bottom;
  opacity: 0.98;
  overflow: hidden;
  box-shadow:
    inset 0 12px 22px rgba(216, 201, 176, 0.24),
    inset 18px 0 26px rgba(159, 185, 149, 0.1);
}

.paper-folds {
  position: absolute;
  inset: 0;
  opacity: 0.62;
  background:
    linear-gradient(83deg, transparent 0 27%, rgba(171, 154, 125, 0.22) 27.5% 28.5%, transparent 29%),
    linear-gradient(104deg, transparent 0 55%, rgba(171, 154, 125, 0.18) 55.5% 56.5%, transparent 57%),
    linear-gradient(172deg, transparent 0 42%, rgba(255, 255, 255, 0.75) 42.5% 43.5%, transparent 44%),
    repeating-linear-gradient(
      to bottom,
      transparent 0 22px,
      rgba(159, 185, 149, 0.18) 22px 23px
    );
  transform: skewY(-4deg);
  pointer-events: none;
}

.envelope-front {
  display: none;
  z-index: 3;
  background:
    linear-gradient(32deg, transparent 49.4%, var(--envelope-edge) 49.8%, transparent 50.3%),
    linear-gradient(-32deg, transparent 49.4%, var(--envelope-edge) 49.8%, transparent 50.3%),
    linear-gradient(160deg, transparent 50%, #efe4d2 50.5%),
    linear-gradient(200deg, transparent 50%, #f8f2e7 50.5%);
  border: 1px solid var(--envelope-edge);
  border-radius: 10px;
  clip-path: polygon(0 32%, 50% 68%, 100% 32%, 100% 100%, 0 100%);
}

.paper-pop {
  z-index: 5;
  width: 40%;
  height: 34%;
  left: 30%;
  top: 40%;
  border: 1px solid rgba(199, 184, 158, 0.82);
  border-radius: 28% 42% 32% 46%;
  background:
    radial-gradient(circle at 28% 26%, rgba(255, 255, 255, 0.9), transparent 30%),
    linear-gradient(132deg, rgba(210, 195, 170, 0.34), transparent 36%),
    linear-gradient(42deg, transparent 0 54%, rgba(176, 158, 130, 0.24) 55% 57%, transparent 58%),
    var(--paper);
  box-shadow:
    inset 12px 2px 18px rgba(190, 174, 146, 0.22),
    inset -10px 8px 18px rgba(255, 255, 255, 0.75),
    0 12px 24px rgba(82, 103, 78, 0.16);
  opacity: 0;
  overflow: hidden;
  transform: translateY(18px) scale(0.16) rotate(-18deg);
  transform-origin: center bottom;
  pointer-events: none;
}

.paper-pop-folds {
  position: absolute;
  inset: 0;
  background:
    linear-gradient(78deg, transparent 0 24%, rgba(147, 128, 96, 0.22) 25% 26%, transparent 27%),
    linear-gradient(114deg, transparent 0 49%, rgba(147, 128, 96, 0.18) 50% 51%, transparent 52%),
    linear-gradient(166deg, transparent 0 66%, rgba(255, 255, 255, 0.8) 67% 68%, transparent 69%),
    repeating-linear-gradient(
      to bottom,
      transparent 0 18px,
      rgba(159, 185, 149, 0.16) 18px 19px
    );
  transform: skewY(-7deg);
}

.envelope-flap {
  opacity: 0;
  z-index: 6;
  background: #faf4e8;
  border: 1px solid var(--envelope-edge);
  border-radius: 10px 10px 4px 4px;
  clip-path: polygon(0 0, 100% 0, 50% 58%);
  transform-origin: top center;
  transition: transform 0.7s cubic-bezier(0.2, 0.8, 0.2, 1);
}

.envelope-flap::after {
  content: none;
  position: absolute;
  width: 42px;
  height: 42px;
  left: 50%;
  top: 45%;
  transform: translate(-50%, -50%);
  border-radius: 50%;
  background: var(--seal);
  box-shadow: inset 0 0 0 7px rgba(255, 255, 255, 0.18);
}

.hint {
  order: -1;
  font-family: "Aa Suibi Hand", serif;
  font-size: 30px;
  font-weight: 800;
  letter-spacing: 0.08em;
  color: #6f1737;
}

.letter-stack {
  position: relative;
  z-index: 3;
  grid-area: 1 / 1;
  width: min(76vw, 560px);
  height: min(88dvh, 760px);
  opacity: 0;
  transform: translateY(34px) scale(0.96);
  pointer-events: none;
  transition:
    opacity 0.65s ease 0.65s,
    transform 0.65s ease 0.65s;
}

.letter-stack:focus {
  outline: none;
}

.stack-sheet,
.letter-card {
  position: absolute;
  inset: 0;
  border: 1px solid rgba(231, 167, 184, 0.78);
  border-radius: 10px;
  background:
    linear-gradient(rgba(255, 253, 248, 0.42), rgba(255, 253, 248, 0.42)),
    url("./素材/信纸.jpg") center / cover no-repeat,
    var(--paper);
  box-shadow: var(--shadow);
}

.stack-sheet::before {
  content: "";
  position: absolute;
  inset: 0 auto 0 0;
  width: 52px;
  border-radius: 10px 0 0 10px;
  background: linear-gradient(
    90deg,
    rgba(94, 35, 52, 0.2),
    rgba(94, 35, 52, 0.08) 42%,
    transparent
  );
  pointer-events: none;
}

.stack-sheet-back {
  transform: translate(24px, 20px) rotate(2.1deg);
  opacity: 0.74;
}

.stack-sheet-middle {
  transform: translate(15px, 8px) rotate(2.4deg);
  opacity: 0.9;
}

.letter-card {
  position: relative;
  height: 100%;
  min-height: 0;
  padding: clamp(24px, 5vw, 46px);
  display: flex;
  flex-direction: column;
  overflow: hidden;
  background:
    linear-gradient(rgba(255, 253, 248, 0.32), rgba(255, 253, 248, 0.32)),
    url("./素材/信纸.jpg") center / cover no-repeat,
    var(--paper);
}

.letter-card.paper-1 {
  background:
    url("./素材/信纸4.jpg") center / cover no-repeat,
    var(--paper);
}

.letter-card.paper-2 {
  background:
    url("./素材/信纸.jpg") center / cover no-repeat,
    var(--paper);
}

.letter-card.paper-3 {
  background:
    url("./素材/信纸3.jpg") center / cover no-repeat,
    var(--paper);
}

.letter-card::before {
  display: none;
}

.letter-card::after {
  content: "";
  position: absolute;
  inset: 0;
  z-index: 0;
  background: rgba(255, 255, 255, 0.2);
  pointer-events: none;
}

.letter-card.paper-1::after {
  background: rgba(255, 255, 255, 0.1);
}

.letter-card.paper-3::after {
  background: rgba(255, 255, 255, 0.25);
}

.ornament {
  position: absolute;
  right: clamp(22px, 6vw, 52px);
  top: clamp(24px, 6vw, 54px);
  width: min(38vw, 210px);
  aspect-ratio: 1;
  color: rgba(201, 34, 78, 0.18);
  pointer-events: none;
}

.ornament::before,
.ornament::after {
  content: "";
  position: absolute;
  border: 2px solid currentColor;
}

.ornament::before {
  width: 74%;
  height: 74%;
  left: 13%;
  top: 13%;
  border-radius: 50%;
  border-style: dashed;
}

.ornament::after {
  width: 42%;
  height: 42%;
  left: 29%;
  top: 29%;
  border-radius: 50% 50% 48% 48%;
  box-shadow:
    -52px -10px 0 -20px currentColor,
    52px 18px 0 -20px currentColor,
    0 58px 0 -22px currentColor;
}

.date {
  display: none;
}

h1 {
  position: relative;
  z-index: 1;
  margin: 0 0 18px;
  font-family: "Zihun Shoujin", "华文行楷", "STXingkai", "Aa Suibi Hand", Georgia, "Times New Roman", serif;
  font-size: clamp(15px, 3.4vw, 22px);
  font-weight: 700;
  line-height: 1.2;
  color: #6f1737;
}

.letter-content {
  position: relative;
  z-index: 1;
  flex: 1;
  min-height: 0;
  overflow: auto;
  font-family: "Zihun Shoujin", "华文行楷", "STXingkai", "Aa Suibi Hand", "STSong", "SimSun", serif;
  font-size: clamp(20px, 4.2vw, 23px);
  line-height: 1.31;
  font-weight: 700;
  color: #351722;
  letter-spacing: -0.08em;
  text-align: justify;
  text-justify: inter-ideograph;
  padding-right: 6px;
  scrollbar-width: none;
  -ms-overflow-style: none;
}

.letter-content.content-short {
  display: flex;
  flex-direction: column;
  justify-content: center;
}

.letter-content::-webkit-scrollbar {
  display: none;
}

.letter-content p {
  margin: 0 0 28px;
}

.letter-content p:last-child {
  margin-bottom: 0;
}

.hard-break {
  display: block;
  height: 0.38em;
}

.signature {
  font-family: "Zihun Shoujin", "华文行楷", "STXingkai", "Aa Suibi Hand", serif;
  font-weight: 700;
  padding-top: 8px;
  text-align: right;
}

.letter-nav {
  position: relative;
  z-index: 2;
  display: grid;
  grid-template-columns: 48px 1fr 48px;
  align-items: center;
  gap: 16px;
  padding-top: 12px;
  flex: 0 0 auto;
}

.nav-button {
  width: 54px;
  height: 54px;
  display: grid;
  place-items: center;
  border: 0;
  border-radius: 50%;
  background: transparent;
  color: var(--rose);
  cursor: pointer;
}

.nav-button:disabled {
  opacity: 0.32;
  cursor: default;
}

.nav-arrow {
  width: 63px;
  height: 63px;
  display: block;
  object-fit: contain;
  mix-blend-mode: multiply;
  filter: saturate(0.95) contrast(1.05);
}

.nav-arrow-left {
  transform: rotate(90deg);
}

.nav-arrow-right {
  transform: rotate(-90deg);
}

.page-count {
  font-family: "华文行楷", "STXingkai", "Aa Suibi Hand", Georgia, "Times New Roman", serif;
  text-align: center;
  color: var(--muted);
  font-size: 11px;
  font-style: italic;
  letter-spacing: 0.1em;
}

.page.opened .intro {
  opacity: 0;
  transform: translateY(-32px) scale(0.92);
  pointer-events: none;
}

.page.opening .envelope-flap,
.page.opened .envelope-flap {
  transform: rotateX(180deg);
}

.page.opening .letter-peek,
.page.opened .letter-peek {
  transform: translateY(-76px);
}

.page.opening .paper-pop,
.page.opened .paper-pop {
  animation: paperPopOpen 1.42s cubic-bezier(0.18, 0.8, 0.18, 1) forwards;
}

.page.opened .letter-stack {
  opacity: 1;
  transform: translateY(0) scale(1);
  pointer-events: auto;
}

.letter-card.turning {
  animation: pageTurn 0.32s ease;
}

@keyframes pageTurn {
  0% {
    opacity: 0.2;
    transform: translateX(18px) rotate(1deg);
  }

  100% {
    opacity: 1;
    transform: translateX(0) rotate(0deg);
  }
}

@keyframes musicSpin {
  to {
    transform: rotate(360deg);
  }
}

@keyframes paperPopOpen {
  0% {
    opacity: 0;
    border-radius: 45% 32% 42% 36%;
    transform: translateY(18px) scale(0.16) rotate(-18deg);
  }

  12% {
    opacity: 1;
    border-radius: 42% 38% 46% 34%;
    transform: translateY(-12px) scale(0.36) rotate(14deg);
  }

  38% {
    opacity: 1;
    border-radius: 34% 44% 28% 40%;
    transform: translateY(-82px) scaleX(0.7) scaleY(0.48) rotate(-7deg);
  }

  72% {
    opacity: 1;
    border-radius: 12px 18px 10px 16px;
    transform: translateY(-142px) scaleX(1.38) scaleY(1.72) rotate(2deg);
  }

  100% {
    opacity: 1;
    border-radius: 8px;
    transform: translateY(-154px) scaleX(1.58) scaleY(1.96) rotate(0deg);
  }
}

@media (max-width: 520px) {
  :root {
    --scene-size: cover;
  }

  body {
    background:
      url("./assets/竖版.png") center / cover no-repeat fixed,
      #f8d9e3;
  }

  .page {
    padding: 12px;
    height: 100svh;
  }

  .page::after {
    background: url("./assets/竖版浮板.png") center 62% / 100% auto no-repeat;
  }

  .envelope-button {
    gap: 0;
    padding: 8px;
    transform: translateY(-4vh);
  }

  .envelope {
    width: min(74vw, 300px);
    transform: translateY(-0.4vh) rotate(-5deg);
  }

  .envelope-button:hover .envelope {
    transform: translateY(calc(-0.4vh - 6px)) rotate(-5deg);
  }

  .hint {
    font-size: 26px;
    letter-spacing: 0.06em;
  }

  .letter-card {
    padding: 22px 18px 20px 26px;
  }

  .letter-content,
  .signature {
    font-weight: 800;
  }

  .letter-stack {
    width: min(82vw, 356px);
    height: min(78svh, 690px);
    transform: translateY(0) scale(0.96);
  }

  .music-button {
    top: max(24px, calc((100dvh - 86dvh) / 2 + 14px));
    right: max(26px, calc((100vw - min(82vw, 356px)) / 2 + 22px));
    width: 42px;
    height: 42px;
  }

  .music-muted {
    inset: 7px;
  }

  .ornament {
    width: 150px;
    opacity: 0.7;
  }

  .letter-nav {
    grid-template-columns: 44px 1fr 44px;
    gap: 10px;
  }

  .nav-button {
    width: 44px;
    height: 44px;
  }

  .prev {
    justify-self: start;
  }

  .next {
    justify-self: end;
  }

  .nav-arrow {
    width: 50px;
    height: 50px;
  }
}

@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after {
    transition-duration: 0.01ms !important;
    animation-duration: 0.01ms !important;
  }
}