/* ============================================
   衡阳市20号信箱 - 复古信笺风格样式
   ============================================ */

/* === CSS Custom Properties === */
:root {
  --bg-paper: hsl(42, 55%, 92%);
  --text-main: hsl(25, 35%, 22%);
  --text-muted: hsl(30, 25%, 42%);
  --primary: hsl(0, 65%, 32%);
  --primary-dark: hsl(0, 65%, 25%);
  --primary-light: hsl(0, 60%, 40%);
  --accent: hsl(35, 40%, 82%);
  --border-color: hsl(30, 30%, 70%);
  --wood-dark: hsl(20, 20%, 12%);
  --wood-mid: hsl(28, 25%, 22%);
  --envelope-light: hsl(42, 50%, 85%);
  --envelope-mid: hsl(40, 45%, 80%);
  --envelope-dark: hsl(38, 40%, 75%);
  --stamp-red: hsl(0, 60%, 28%);
  --seal-red: hsl(0, 65%, 30%);
  --seal-dark: hsl(0, 70%, 22%);
  --nav-red: hsl(0, 60%, 30%);
  --nav-text: hsl(40, 60%, 90%);
}

/* === Reset & Base === */
*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  font-size: 16px;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

body {
  font-family: 'SimSun', 'STSong', '宋体', 'KaiTi', 'STKaiti', '楷体', serif;
  color: var(--text-main);
  background: var(--wood-dark);
  min-height: 100vh;
  overflow-x: hidden;
}

a {
  color: inherit;
  text-decoration: none;
}

/* === App Shell === */
#app {
  min-height: 100vh;
  position: relative;
}

/* === Page Container (shared) === */
.page {
  display: none;
  min-height: 100vh;
}

.page.active {
  display: flex;
}

.page.fade-out {
  display: flex;
}

/* === Envelope Page === */
.page-envelope {
  align-items: center;
  justify-content: center;
  flex-direction: column;
  position: relative;
  overflow: hidden;
  background: radial-gradient(ellipse at center, var(--wood-mid) 0%, var(--wood-dark) 100%);
  min-height: 100vh;
}

.envelope-wood-texture {
  position: absolute;
  inset: 0;
  opacity: 0.4;
  pointer-events: none;
  background-image:
    repeating-linear-gradient(90deg, transparent, transparent 3px, rgba(0,0,0,0.04) 3px, rgba(0,0,0,0.04) 4px),
    repeating-linear-gradient(0deg, transparent, transparent 80px, rgba(80,40,20,0.08) 80px, rgba(80,40,20,0.08) 82px);
}

.envelope-spotlight {
  position: absolute;
  inset: 0;
  pointer-events: none;
  background: radial-gradient(ellipse at 50% 45%, rgba(255,220,150,0.08) 0%, transparent 50%);
}

.envelope-stage {
  position: relative;
  perspective: 1500px;
}

/* Envelope floating animation */
.envelope-float {
  position: relative;
  cursor: pointer;
  transform-style: preserve-3d;
  animation: envelopeFloat 4s ease-in-out infinite;
}

@keyframes envelopeFloat {
  0%, 100% { transform: translateY(0) rotateX(5deg); }
  50% { transform: translateY(-8px) rotateX(2deg); }
}

.envelope-float:hover {
  animation-play-state: paused;
  transform: translateY(-12px) rotateX(2deg);
}

.envelope-float.opening {
  animation: none;
  opacity: 0;
  transform: translateY(-20px);
  transition: opacity 0.6s, transform 0.6s;
}

/* Envelope body */
.envelope-body {
  position: relative;
  width: 320px;
  height: 220px;
  border-radius: 2px;
  box-shadow:
    0 30px 60px -15px rgba(0,0,0,0.6),
    0 0 0 1px rgba(139,90,43,0.15);
  background: linear-gradient(135deg, var(--envelope-light) 0%, var(--envelope-mid) 50%, var(--envelope-dark) 100%);
}

@media (min-width: 768px) {
  .envelope-body {
    width: 480px;
    height: 320px;
  }
}

.envelope-body .texture {
  position: absolute;
  inset: 0;
  pointer-events: none;
  opacity: 0.3;
  mix-blend-mode: multiply;
  border-radius: 2px;
  background-image: url("data:image/svg+xml,%3Csvg viewBox='0 0 200 200' xmlns='http://www.w3.org/2000/svg'%3E%3Cfilter id='noise'%3E%3CfeTurbulence type='fractalNoise' baseFrequency='0.9' numOctaves='4' stitchTiles='stitch'/%3E%3C/filter%3E%3Crect width='100%25' height='100%25' filter='url(%23noise)'/%3E%3C/svg%3E");
  background-size: 200px 200px;
}

/* Envelope flap */
.envelope-flap {
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 110px;
  transform-origin: top center;
  clip-path: polygon(0 0, 100% 0, 50% 100%);
  background: linear-gradient(135deg, hsl(40,45%,82%) 0%, hsl(38,40%,77%) 100%);
  border-bottom: 1px solid rgba(139,90,43,0.2);
  transition: transform 0.8s ease-in-out;
  z-index: 2;
}

@media (min-width: 768px) {
  .envelope-flap {
    height: 160px;
  }
}

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

/* Fire Seal (火漆印章) */
.fire-seal {
  position: absolute;
  top: 85px;
  left: 50%;
  transform: translateX(-50%);
  width: 56px;
  height: 56px;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 10;
  background: radial-gradient(circle at 35% 35%, hsl(0,60%,40%) 0%, var(--seal-red) 50%, var(--seal-dark) 100%);
  box-shadow:
    0 4px 8px rgba(0,0,0,0.4),
    inset 0 2px 4px rgba(255,200,200,0.2),
    inset 0 -2px 4px rgba(0,0,0,0.3);
  transition: opacity 0.5s, transform 0.5s;
}

@media (min-width: 768px) {
  .fire-seal {
    top: 125px;
    width: 80px;
    height: 80px;
  }
}

.fire-seal.hidden {
  opacity: 0;
  transform: translateX(-50%) scale(0.5);
}

.fire-seal span {
  color: hsl(40,60%,85%);
  font-size: 12px;
  font-weight: bold;
  font-family: 'KaiTi', 'STKaiti', '楷体', serif;
  letter-spacing: 0.1em;
  text-shadow: 0 1px 2px rgba(0,0,0,0.5);
}

@media (min-width: 768px) {
  .fire-seal span {
    font-size: 14px;
  }
}

/* Stamp (邮票) */
.envelope-stamp {
  position: absolute;
  top: 12px;
  right: 12px;
  width: 56px;
  height: 72px;
  background: var(--bg-paper);
  padding: 2px;
  box-shadow: 0 2px 4px rgba(0,0,0,0.2);
  border: 1px dashed rgba(139,90,43,0.4);
  z-index: 3;
}

@media (min-width: 768px) {
  .envelope-stamp {
    top: 16px;
    right: 16px;
    width: 80px;
    height: 96px;
  }
}

.envelope-stamp .stamp-inner {
  width: 100%;
  height: 100%;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  background: linear-gradient(180deg, hsl(0,55%,35%) 0%, var(--stamp-red) 100%);
  color: hsl(40,60%,90%);
}

.envelope-stamp .stamp-text-top {
  font-size: 8px;
  font-weight: bold;
  margin-bottom: 2px;
}

@media (min-width: 768px) {
  .envelope-stamp .stamp-text-top {
    font-size: 10px;
  }
}

.envelope-stamp .stamp-price {
  font-family: 'KaiTi', 'STKaiti', '楷体', serif;
  font-size: 16px;
  font-weight: bold;
}

@media (min-width: 768px) {
  .envelope-stamp .stamp-price {
    font-size: 20px;
  }
}

.envelope-stamp .stamp-text-bottom {
  font-size: 7px;
  opacity: 0.8;
  margin-top: 2px;
  color: hsl(40,60%,85%);
}

@media (min-width: 768px) {
  .envelope-stamp .stamp-text-bottom {
    font-size: 9px;
  }
}

/* Postmark (邮戳) */
.postmark {
  position: absolute;
  top: 24px;
  right: 24px;
  width: 64px;
  height: 64px;
  border-radius: 50%;
  border: 2px solid rgba(139,0,0,0.7);
  display: flex;
  align-items: center;
  justify-content: center;
  pointer-events: none;
  transform: rotate(-15deg);
  z-index: 4;
}

@media (min-width: 768px) {
  .postmark {
    top: 32px;
    right: 32px;
    width: 80px;
    height: 80px;
  }
}

.postmark .postmark-inner {
  text-align: center;
}

.postmark .postmark-city {
  font-size: 7px;
  font-weight: bold;
  color: rgba(139,0,0,0.8);
}

@media (min-width: 768px) {
  .postmark .postmark-city {
    font-size: 9px;
  }
}

.postmark .postmark-date {
  font-size: 6px;
  color: rgba(139,0,0,0.7);
  margin: 2px 0;
}

@media (min-width: 768px) {
  .postmark .postmark-date {
    font-size: 8px;
  }
}

.postmark .postmark-branch {
  font-size: 7px;
  font-weight: bold;
  color: rgba(139,0,0,0.8);
}

@media (min-width: 768px) {
  .postmark .postmark-branch {
    font-size: 9px;
  }
}

/* Return address (寄件人) */
.return-address {
  position: absolute;
  bottom: 16px;
  right: 20px;
  text-align: right;
  z-index: 3;
}

@media (min-width: 768px) {
  .return-address {
    bottom: 24px;
    right: 32px;
  }
}

.return-address .address-name {
  font-family: 'KaiTi', 'STKaiti', '楷体', serif;
  font-size: 14px;
  font-weight: 500;
  color: hsl(25,30%,28%);
  letter-spacing: 0.05em;
}

@media (min-width: 768px) {
  .return-address .address-name {
    font-size: 16px;
  }
}

.return-address .postal-code {
  font-family: 'Courier New', monospace;
  font-size: 10px;
  color: hsl(25,25%,40%);
  margin-top: 4px;
  letter-spacing: 0.15em;
}

@media (min-width: 768px) {
  .return-address .postal-code {
    font-size: 12px;
  }
}

/* Corner wear on envelope */
.envelope-corner-wear {
  position: absolute;
  pointer-events: none;
  z-index: 5;
}
.envelope-corner-wear.tl {
  top: 0; left: 0;
  width: 24px; height: 24px;
  background: linear-gradient(135deg, rgba(180,150,120,0.4) 0%, transparent 100%);
  border-radius: 0 0 100% 0;
}
.envelope-corner-wear.tr {
  top: 0; right: 0;
  width: 24px; height: 24px;
  background: linear-gradient(225deg, rgba(180,150,120,0.4) 0%, transparent 100%);
  border-radius: 0 0 0 100%;
}
.envelope-corner-wear.bl {
  bottom: 0; left: 0;
  width: 32px; height: 32px;
  background: linear-gradient(45deg, rgba(160,130,100,0.4) 0%, transparent 100%);
  border-radius: 0 100% 0 0;
}
.envelope-corner-wear.br {
  bottom: 0; right: 0;
  width: 32px; height: 32px;
  background: linear-gradient(315deg, rgba(160,130,100,0.4) 0%, transparent 100%);
  border-radius: 100% 0 0 0;
}

/* Click hint */
.click-hint {
  position: absolute;
  bottom: -48px;
  left: 50%;
  transform: translateX(-50%);
  text-align: center;
  white-space: nowrap;
  color: hsl(40,40%,70%);
  font-size: 14px;
  letter-spacing: 0.25em;
  animation: hintPulse 2s ease-in-out infinite;
}

@media (min-width: 768px) {
  .click-hint {
    bottom: -64px;
    font-size: 16px;
  }
}

@keyframes hintPulse {
  0%, 100% { opacity: 0.5; }
  50% { opacity: 1; }
}

/* Letter slide-out during opening */
.letter-slide-out {
  position: absolute;
  top: 60px;
  left: 20px;
  right: 20px;
  z-index: 0;
  opacity: 0;
  pointer-events: none;
  transform: translateY(0);
  transition: all 1s cubic-bezier(0.16, 1, 0.3, 1);
}

@media (min-width: 768px) {
  .letter-slide-out {
    top: 90px;
    left: 30px;
    right: 30px;
  }
}

.letter-slide-out.visible {
  opacity: 1;
  transform: translateY(-180px);
}

.letter-slide-out .slide-paper {
  width: 100%;
  height: 200px;
  border-radius: 2px;
  box-shadow: 0 10px 30px rgba(0,0,0,0.3);
  background: linear-gradient(180deg, var(--bg-paper) 0%, hsl(40,50%,88%) 100%);
  position: relative;
}

@media (min-width: 768px) {
  .letter-slide-out .slide-paper {
    height: 280px;
  }
}

.letter-slide-out .slide-texture {
  position: absolute;
  inset: 0;
  opacity: 0.2;
  mix-blend-mode: multiply;
  background-image: url("data:image/svg+xml,%3Csvg viewBox='0 0 200 200' xmlns='http://www.w3.org/2000/svg'%3E%3Cfilter id='noise'%3E%3CfeTurbulence type='fractalNoise' baseFrequency='0.9' numOctaves='4' stitchTiles='stitch'/%3E%3C/filter%3E%3Crect width='100%25' height='100%25' filter='url(%23noise)'/%3E%3C/svg%3E");
  background-size: 200px 200px;
}

.letter-slide-out .slide-title {
  text-align: center;
  color: hsl(0,65%,28%);
  font-size: 20px;
  font-weight: bold;
  font-family: 'KaiTi', 'STKaiti', '楷体', serif;
  letter-spacing: 0.3em;
  padding-left: 0.3em;
  margin-top: 24px;
}

@media (min-width: 768px) {
  .letter-slide-out .slide-title {
    font-size: 24px;
    margin-top: 32px;
  }
}

.letter-slide-out .slide-lines {
  margin: 16px 24px 0;
  display: flex;
  flex-direction: column;
  gap: 8px;
}

@media (min-width: 768px) {
  .letter-slide-out .slide-lines {
    margin: 16px 32px 0;
  }
}

.letter-slide-out .slide-line {
  height: 8px;
  background: hsla(25,25%,50%,0.2);
  border-radius: 9999px;
}

.slide-line.w-3-4 { width: 75%; }
.slide-line.w-full { width: 100%; }
.slide-line.w-5-6 { width: 83.33%; }

/* Bottom motto */
.bottom-motto {
  position: absolute;
  bottom: 24px;
  left: 0;
  right: 0;
  text-align: center;
  color: hsla(40,30%,50%,0.4);
  font-size: 12px;
  letter-spacing: 0.5em;
}

/* ============================================
   LETTER LAYOUT (inner pages)
   ============================================ */

.page-inner {
  align-items: center;
  justify-content: center;
  padding: 16px;
  position: relative;
  overflow: hidden;
  background: linear-gradient(135deg, hsl(25,30%,15%) 0%, var(--wood-mid) 50%, var(--wood-dark) 100%);
}

@media (min-width: 768px) {
  .page-inner {
    padding: 32px;
  }
}

.letter-wood-texture {
  position: absolute;
  inset: 0;
  opacity: 0.3;
  pointer-events: none;
  background-image:
    repeating-linear-gradient(90deg, transparent, transparent 2px, rgba(0,0,0,0.03) 2px, rgba(0,0,0,0.03) 4px),
    repeating-linear-gradient(0deg, transparent, transparent 60px, rgba(139,90,43,0.05) 60px, rgba(139,90,43,0.05) 61px);
}

.letter-wrapper {
  position: relative;
  width: 100%;
  max-width: 768px;
  display: flex;
}

/* Side navigation tabs */
.nav-tabs {
  display: none;
  flex-direction: column;
  gap: 8px;
  padding-top: 80px;
  margin-left: -12px;
  z-index: 10;
  flex-shrink: 0;
}

@media (min-width: 768px) {
  .nav-tabs {
    display: flex;
  }
}

.nav-tab {
  position: relative;
  padding: 8px 16px;
  font-size: 14px;
  font-weight: 500;
  background: var(--nav-red);
  color: var(--nav-text);
  box-shadow: 0 2px 4px rgba(0,0,0,0.2);
  cursor: pointer;
  transition: all 0.3s ease;
  writing-mode: vertical-rl;
  text-orientation: upright;
  clip-path: polygon(0 0, 100% 5%, 100% 95%, 0 100%);
  letter-spacing: 0.2em;
  border: none;
  font-family: 'KaiTi', 'STKaiti', '楷体', 'SimSun', serif;
}

.nav-tab:hover {
  box-shadow: 0 4px 8px rgba(0,0,0,0.3);
  transform: translateX(-4px);
}

.nav-tab.active {
  transform: translateX(-8px);
  box-shadow: 0 4px 8px rgba(0,0,0,0.3);
  background: var(--primary-dark);
}

/* Mobile top nav */
.mobile-nav {
  display: flex;
  gap: 4px;
  position: absolute;
  top: -8px;
  left: 50%;
  transform: translateX(-50%);
  z-index: 20;
}

@media (min-width: 768px) {
  .mobile-nav {
    display: none;
  }
}

.mobile-nav-tab {
  padding: 6px 12px;
  font-size: 12px;
  font-weight: 500;
  background: var(--nav-red);
  color: var(--nav-text);
  box-shadow: 0 2px 4px rgba(0,0,0,0.2);
  cursor: pointer;
  transition: all 0.3s ease;
  clip-path: polygon(5% 0, 95% 0, 100% 100%, 0 100%);
  border: none;
  font-family: 'KaiTi', 'STKaiti', '楷体', 'SimSun', serif;
}

.mobile-nav-tab:hover {
  transform: translateY(-2px);
}

.mobile-nav-tab.active {
  transform: translateY(-4px);
  background: var(--primary-dark);
}

/* Letter paper */
.letter-paper {
  position: relative;
  flex: 1;
  min-height: 600px;
  border-radius: 2px;
  box-shadow:
    0 25px 50px -12px rgba(0,0,0,0.5),
    0 0 0 1px rgba(139,90,43,0.1);
  background: linear-gradient(180deg,
    var(--bg-paper) 0%,
    hsl(40,50%,88%) 30%,
    hsl(42,45%,85%) 70%,
    hsl(38,40%,82%) 100%
  );
  overflow: hidden;
  transition: opacity 0.6s, transform 0.6s cubic-bezier(0.16,1,0.3,1);
}

@media (min-width: 768px) {
  .letter-paper {
    min-height: 700px;
  }
}

.letter-paper.entering {
  animation: paperEnter 0.6s cubic-bezier(0.16,1,0.3,1);
}

@keyframes paperEnter {
  from {
    opacity: 0;
    transform: rotateY(-15deg) translateX(-50px);
  }
  to {
    opacity: 1;
    transform: rotateY(0) translateX(0);
  }
}

/* Paper texture */
.paper-texture {
  position: absolute;
  inset: 0;
  pointer-events: none;
  opacity: 0.4;
  mix-blend-mode: multiply;
  background-image: url("data:image/svg+xml,%3Csvg viewBox='0 0 200 200' xmlns='http://www.w3.org/2000/svg'%3E%3Cfilter id='noise2'%3E%3CfeTurbulence type='fractalNoise' baseFrequency='0.85' numOctaves='4' stitchTiles='stitch'/%3E%3C/filter%3E%3Crect width='100%25' height='100%25' filter='url(%23noise2)'/%3E%3C/svg%3E");
  background-size: 200px 200px;
}

/* Fold marks */
.fold-marks {
  position: absolute;
  inset: 0;
  pointer-events: none;
  background:
    linear-gradient(180deg,
      transparent 0%,
      transparent 32%,
      rgba(139,90,43,0.08) 33%,
      transparent 34%,
      transparent 65%,
      rgba(139,90,43,0.06) 66%,
      transparent 67%,
      transparent 100%
    );
}

/* Letter header */
.letter-header {
  position: relative;
  padding-top: 40px;
  padding-bottom: 24px;
  text-align: center;
  border-bottom: 2px dashed hsla(0,50%,35%,0.3);
  margin: 0 32px;
}

@media (min-width: 768px) {
  .letter-header {
    padding-top: 48px;
    margin: 0 48px;
  }
}

.letter-header h1 {
  font-size: 36px;
  font-weight: bold;
  color: hsl(0,65%,28%);
  font-family: 'KaiTi', 'STKaiti', '楷体', serif;
  letter-spacing: 0.5em;
  padding-left: 0.5em;
  text-shadow: 1px 1px 0 rgba(139,0,0,0.1);
}

@media (min-width: 768px) {
  .letter-header h1 {
    font-size: 48px;
  }
}

.letter-header .subtitle {
  margin-top: 8px;
  font-size: 12px;
  color: hsla(0,40%,35%,0.6);
  letter-spacing: 0.25em;
}

/* Red decorative line below header */
.letter-decorative-line {
  position: absolute;
  top: 112px;
  left: 32px;
  right: 32px;
  height: 2px;
  background: linear-gradient(90deg, transparent, hsla(0,50%,40%,0.5), transparent);
}

@media (min-width: 768px) {
  .letter-decorative-line {
    top: 128px;
    left: 48px;
    right: 48px;
  }
}

/* Letter content area */
.letter-content {
  position: relative;
  padding: 32px 24px;
}

@media (min-width: 768px) {
  .letter-content {
    padding: 40px 48px;
  }
}

/* Letter footer */
.letter-footer {
  position: absolute;
  bottom: 16px;
  left: 0;
  right: 0;
  text-align: center;
  font-size: 12px;
  color: hsla(25,25%,42%,0.5);
  font-family: serif;
}

/* Corner wear on letter */
.letter-corner-wear {
  position: absolute;
  pointer-events: none;
  z-index: 5;
}
.letter-corner-wear.tl {
  top: 0; left: 0;
  width: 32px; height: 32px;
  background: linear-gradient(135deg, hsla(25,20%,65%,0.3) 0%, transparent 100%);
  border-radius: 0 0 100% 0;
}
.letter-corner-wear.tr {
  top: 0; right: 0;
  width: 32px; height: 32px;
  background: linear-gradient(225deg, hsla(25,20%,65%,0.3) 0%, transparent 100%);
  border-radius: 0 0 0 100%;
}
.letter-corner-wear.bl {
  bottom: 0; left: 0;
  width: 40px; height: 40px;
  background: linear-gradient(45deg, hsla(25,20%,60%,0.3) 0%, transparent 100%);
  border-radius: 0 100% 0 0;
}
.letter-corner-wear.br {
  bottom: 0; right: 0;
  width: 40px; height: 40px;
  background: linear-gradient(315deg, hsla(25,20%,60%,0.3) 0%, transparent 100%);
  border-radius: 100% 0 0 0;
}

/* ============================================
   ABOUT PAGE
   ============================================ */
.about-section-title {
  text-align: center;
  margin-bottom: 32px;
}

.about-section-title h2 {
  font-size: 24px;
  font-weight: bold;
  color: hsl(0,60%,30%);
  font-family: 'KaiTi', 'STKaiti', '楷体', serif;
}

@media (min-width: 768px) {
  .about-section-title h2 {
    font-size: 30px;
  }
}

.section-title-decoration {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  margin-top: 8px;
}

.section-title-decoration span.line {
  width: 48px;
  height: 1px;
  background: hsla(0,50%,40%,0.4);
}

.section-title-decoration span.label {
  font-size: 12px;
  color: hsl(0,40%,35%);
}

.about-paragraphs {
  display: flex;
  flex-direction: column;
  gap: 20px;
  color: var(--text-main);
  line-height: 1.75;
  font-size: 16px;
}

@media (min-width: 768px) {
  .about-paragraphs {
    font-size: 18px;
  }
}

.about-paragraphs p {
  text-indent: 2em;
  font-family: 'SimSun', 'STSong', '宋体', serif;
  text-shadow: 0 0 1px rgba(0,0,0,0.05);
  opacity: 0;
  transform: translateY(10px);
  transition: opacity 0.5s, transform 0.5s;
}

.about-paragraphs p.visible {
  opacity: 1;
  transform: translateY(0);
}

/* Stamp/seal decoration */
.seal-decoration {
  display: flex;
  justify-content: flex-end;
  margin-top: 40px;
  padding-right: 16px;
}

.seal-circle {
  width: 80px;
  height: 80px;
  border-radius: 50%;
  border: 3px solid hsla(0,65%,35%,0.8);
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  box-shadow: inset 0 0 10px rgba(139,0,0,0.1);
  color: hsla(0,65%,35%,0.9);
  font-family: 'KaiTi', 'STKaiti', '楷体', serif;
  transform: rotate(-15deg);
  opacity: 0;
  transition: opacity 0.6s, transform 0.6s;
}

@media (min-width: 768px) {
  .seal-circle {
    width: 96px;
    height: 96px;
  }
}

.seal-circle.visible {
  opacity: 1;
  transform: rotate(-15deg) scale(1);
}

.seal-circle .seal-top {
  font-size: 10px;
  font-weight: bold;
  letter-spacing: 0.25em;
}

.seal-circle .seal-main {
  font-size: 16px;
  font-weight: bold;
  margin-top: 2px;
}

.seal-circle .seal-bottom {
  font-size: 8px;
  opacity: 0.7;
  margin-top: 2px;
}

@media (min-width: 768px) {
  .seal-circle .seal-top { font-size: 12px; }
  .seal-circle .seal-main { font-size: 18px; }
  .seal-circle .seal-bottom { font-size: 10px; }
}

/* ============================================
   HISTORY PAGE
   ============================================ */

.history-intro {
  text-align: center;
  color: hsl(25,30%,30%);
  font-style: italic;
  margin-bottom: 32px;
  font-size: 14px;
  font-family: 'SimSun', 'STSong', '宋体', serif;
  opacity: 0;
  transform: translateY(10px);
  transition: opacity 0.5s, transform 0.5s;
}

@media (min-width: 768px) {
  .history-intro {
    font-size: 16px;
  }
}

.history-intro.visible {
  opacity: 1;
  transform: translateY(0);
}

/* Timeline */
.timeline {
  position: relative;
  padding-left: 32px;
  display: flex;
  flex-direction: column;
  gap: 32px;
}

@media (min-width: 768px) {
  .timeline {
    padding-left: 48px;
  }
}

.timeline-line {
  position: absolute;
  left: 12px;
  top: 8px;
  bottom: 8px;
  width: 2px;
  background: linear-gradient(180deg, hsl(0,50%,40%) 0%, hsl(0,40%,50%) 50%, hsl(0,30%,60%) 100%);
}

@media (min-width: 768px) {
  .timeline-line {
    left: 20px;
  }
}

.timeline-item {
  position: relative;
  opacity: 0;
  transform: translateX(-20px);
  transition: opacity 0.5s, transform 0.5s;
}

.timeline-item.visible {
  opacity: 1;
  transform: translateX(0);
}

.timeline-dot {
  position: absolute;
  left: -26px;
  top: 0;
  width: 24px;
  height: 24px;
  border-radius: 50%;
  background: hsl(0,60%,32%);
  display: flex;
  align-items: center;
  justify-content: center;
  box-shadow: 0 2px 8px rgba(139,0,0,0.3);
  color: hsl(40,60%,90%);
  font-size: 10px;
  font-weight: bold;
  z-index: 2;
}

@media (min-width: 768px) {
  .timeline-dot {
    left: -34px;
    width: 32px;
    height: 32px;
    font-size: 12px;
  }
}

.timeline-card {
  margin-left: 8px;
  padding: 16px;
  border-radius: 2px;
  border: 1px solid hsla(25,30%,60%,0.5);
  background: hsla(42,55%,95%,0.6);
  box-shadow: 2px 2px 8px rgba(139,90,43,0.1);
}

@media (min-width: 768px) {
  .timeline-card {
    padding: 20px;
  }
}

.timeline-card .timeline-card-header {
  display: flex;
  align-items: baseline;
  gap: 12px;
  margin-bottom: 8px;
}

.timeline-card .timeline-year {
  font-family: 'KaiTi', 'STKaiti', '楷体', serif;
  font-size: 18px;
  font-weight: bold;
  color: hsl(0,60%,32%);
  font-variant-numeric: tabular-nums;
}

@media (min-width: 768px) {
  .timeline-card .timeline-year {
    font-size: 20px;
  }
}

.timeline-card .timeline-title {
  font-size: 16px;
  font-weight: 600;
  color: var(--text-main);
}

@media (min-width: 768px) {
  .timeline-card .timeline-title {
    font-size: 18px;
  }
}

.timeline-card .timeline-desc {
  font-size: 14px;
  color: hsl(25,30%,30%);
  line-height: 1.625;
  font-family: 'SimSun', 'STSong', '宋体', serif;
}

@media (min-width: 768px) {
  .timeline-card .timeline-desc {
    font-size: 16px;
  }
}

.timeline-end {
  position: relative;
  opacity: 0;
  transition: opacity 0.5s;
}

.timeline-end.visible {
  opacity: 1;
}

.timeline-end-dot {
  position: absolute;
  left: -22px;
  top: 8px;
  width: 20px;
  height: 20px;
  border-radius: 50%;
  border: 2px solid hsla(0,50%,40%,0.5);
}

@media (min-width: 768px) {
  .timeline-end-dot {
    left: -30px;
    width: 24px;
    height: 24px;
  }
}

.timeline-end-text {
  margin-left: 8px;
  text-align: center;
  color: hsl(25,25%,40%);
  font-size: 14px;
  font-style: italic;
  padding-top: 8px;
}

/* ============================================
   CONTACT PAGE
   ============================================ */

.confidential-badge {
  display: flex;
  justify-content: center;
  margin-bottom: 32px;
  opacity: 0;
  transform: scale(0.9);
  transition: opacity 0.5s, transform 0.5s;
}

.confidential-badge.visible {
  opacity: 1;
  transform: scale(1);
}

.confidential-badge-inner {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 8px 16px;
  border: 2px solid hsl(0,60%,35%);
  border-radius: 2px;
  background: linear-gradient(135deg, hsl(0,60%,95%) 0%, hsl(0,50%,90%) 100%);
  font-family: 'KaiTi', 'STKaiti', '楷体', serif;
  color: hsl(0,65%,28%);
  font-size: 14px;
  font-weight: bold;
  letter-spacing: 0.25em;
}

@media (min-width: 768px) {
  .confidential-badge-inner {
    font-size: 16px;
  }
}

.confidential-badge-inner svg {
  width: 16px;
  height: 16px;
  color: hsl(0,60%,32%);
}

@media (min-width: 768px) {
  .confidential-badge-inner svg {
    width: 20px;
    height: 20px;
  }
}

/* Contact items */
.contact-items {
  display: flex;
  flex-direction: column;
  gap: 0;
}

.contact-item {
  display: flex;
  align-items: flex-start;
  gap: 16px;
  padding: 16px;
  border-bottom: 1px dashed hsla(25,30%,60%,0.5);
  opacity: 0;
  transform: translateX(-10px);
  transition: opacity 0.4s, transform 0.4s;
}

.contact-item.visible {
  opacity: 1;
  transform: translateX(0);
}

.contact-item-icon {
  flex-shrink: 0;
  width: 40px;
  height: 40px;
  border-radius: 50%;
  background: hsla(0,55%,30%,0.1);
  display: flex;
  align-items: center;
  justify-content: center;
}

.contact-item-icon svg {
  width: 20px;
  height: 20px;
  color: hsl(0,60%,32%);
}

.contact-item-label {
  font-size: 12px;
  color: hsl(25,25%,40%);
  margin-bottom: 4px;
  letter-spacing: 0.15em;
}

.contact-item-value {
  font-size: 16px;
  color: var(--text-main);
  font-weight: 500;
  font-family: 'SimSun', 'STSong', '宋体', serif;
}

@media (min-width: 768px) {
  .contact-item-value {
    font-size: 18px;
  }
}

.contact-item-value.mono {
  font-family: 'Courier New', monospace;
  letter-spacing: 0.25em;
}

/* Notice box */
.notice-box {
  margin-top: 32px;
  padding: 16px;
  border: 1px solid hsla(0,50%,40%,0.3);
  background: hsla(0,50%,95%,0.5);
  border-radius: 2px;
  opacity: 0;
  transform: translateY(10px);
  transition: opacity 0.5s, transform 0.5s;
}

.notice-box.visible {
  opacity: 1;
  transform: translateY(0);
}

.notice-box .notice-header {
  display: flex;
  align-items: center;
  gap: 8px;
  margin-bottom: 8px;
}

.notice-box .notice-bar {
  width: 6px;
  height: 16px;
  background: hsl(0,60%,32%);
}

.notice-box .notice-title {
  font-size: 14px;
  font-weight: bold;
  color: hsl(0,60%,30%);
  font-family: 'KaiTi', 'STKaiti', '楷体', serif;
}

.notice-box .notice-text {
  font-size: 14px;
  color: hsl(25,30%,30%);
  line-height: 1.625;
  padding-left: 14px;
  font-family: 'SimSun', 'STSong', '宋体', serif;
}

/* Security level badge (absolute positioned) */
.security-level-badge {
  position: absolute;
  top: 128px;
  right: 24px;
  opacity: 0;
  transform: rotate(-10deg);
  transition: opacity 0.5s, transform 0.5s;
  pointer-events: none;
  z-index: 5;
}

@media (min-width: 768px) {
  .security-level-badge {
    top: 160px;
    right: 40px;
  }
}

.security-level-badge.visible {
  opacity: 0.8;
  transform: rotate(-10deg);
}

.security-level-badge-inner {
  padding: 4px 12px;
  border: 2px solid hsl(0,65%,35%);
  color: hsl(0,65%,30%);
  font-size: 12px;
  font-weight: bold;
  letter-spacing: 0.25em;
  font-family: 'KaiTi', 'STKaiti', '楷体', serif;
}

@media (min-width: 768px) {
  .security-level-badge-inner {
    font-size: 14px;
  }
}

/* ============================================
   404 PAGE
   ============================================ */

.page-404 {
  align-items: center;
  justify-content: center;
  flex-direction: column;
  min-height: 100vh;
  background: var(--wood-dark);
  color: var(--bg-paper);
}

.page-404 h1 {
  font-size: 60px;
  font-weight: bold;
  margin-bottom: 16px;
}

.page-404 p {
  font-size: 18px;
  color: var(--text-muted);
  margin-bottom: 32px;
}

.page-404 a {
  color: hsl(0,60%,40%);
  text-decoration: underline;
  cursor: pointer;
  font-size: 16px;
}

.page-404 a:hover {
  color: hsl(0,65%,32%);
}

/* ============================================
   RESPONSIVE
   ============================================ */

@media (max-width: 767px) {
  .letter-header h1 {
    font-size: 28px;
  }

  .letter-header {
    padding-top: 32px;
    margin: 0 20px;
  }

  .letter-content {
    padding: 24px 20px;
  }

  .letter-paper {
    min-height: 500px;
  }
}