/* ==========================================================================
   envelope.css — Envelope page styles with 3 opening animation variants
   信封页面样式，含 3 种开启动画变体（抽出式、翻转式、飘散式）
   ========================================================================== */

/* --- Envelope screen container / 信封屏幕容器 --- */
#envelope-screen {
  background: linear-gradient(135deg, var(--bg-black) 0%, var(--bg-dark-rose) 40%, var(--bg-deep-magenta) 100%);
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  overflow: hidden;
}

/* --- Envelope wrapper (holds envelope + hint) / 信封包装器 --- */
.envelope-wrapper {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 24px;
  -webkit-transform: translateZ(0);
  transform: translateZ(0);
}

/* --- Envelope body / 信封主体 --- */
.envelope {
  position: relative;
  width: 280px;
  height: 200px;
  background: linear-gradient(145deg, #1A0A14 0%, #2D0A24 100%);
  border: 1px solid rgba(255, 20, 147, 0.15);
  border-radius: 6px;
  box-shadow:
    0 0 30px rgba(255, 20, 147, 0.2),
    0 0 60px rgba(255, 20, 147, 0.1);
  cursor: pointer;
  -webkit-transform: translateZ(0);
  transform: translateZ(0);
  /* 3D perspective context for flip + pull-out */
  -webkit-perspective: 800px;
  perspective: 800px;
}

/* --- Envelope flap (top triangle) / 信封盖（顶部三角形） --- */
.envelope-flap {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 80px;
  background: linear-gradient(180deg, #2D1020 0%, #220E1C 100%);
  -webkit-clip-path: polygon(0 0, 50% 80px, 100% 0);
  clip-path: polygon(0 0, 50% 80px, 100% 0);
  z-index: 3;
  -webkit-transform-origin: top center;
  transform-origin: top center;
  -webkit-transform-style: preserve-3d;
  transform-style: preserve-3d;
  -webkit-transition: transform 0.6s cubic-bezier(0.4, 0, 0.2, 1);
  transition: transform 0.6s cubic-bezier(0.4, 0, 0.2, 1);
}

/* --- Wax seal decoration / 火漆印章装饰 --- */
.envelope-seal {
  position: absolute;
  top: 38px;
  left: 50%;
  width: 40px;
  height: 40px;
  -webkit-transform: translateX(-50%) translateZ(1px);
  transform: translateX(-50%) translateZ(1px);
  border-radius: 50%;
  background: radial-gradient(circle at 35% 35%, #FFD700, #B8860B 60%, #8B6914 100%);
  box-shadow:
    0 2px 8px rgba(0, 0, 0, 0.5),
    inset 0 1px 2px rgba(255, 255, 255, 0.3);
  z-index: 4;
  pointer-events: none;
}

/* Seal heart emboss / 印章爱心浮雕 */
.envelope-seal::after {
  content: '\2764';
  position: absolute;
  top: 50%;
  left: 50%;
  -webkit-transform: translate(-50%, -50%);
  transform: translate(-50%, -50%);
  font-size: 16px;
  color: rgba(139, 69, 20, 0.6);
  text-shadow: 0 1px 0 rgba(255, 215, 0, 0.4);
}

/* --- Envelope text / 信封文字 --- */
.envelope-text {
  position: absolute;
  bottom: 30px;
  left: 0;
  right: 0;
  text-align: center;
  font-size: 18px;
  font-style: italic;
  letter-spacing: 2px;
  color: var(--gold-soft);
  z-index: 2;
  pointer-events: none;
}

/* --- Envelope text as image / 信封文字图片模式 --- */
.envelope-text img {
  max-width: 80%;
  max-height: 40px;
  margin: 0 auto;
  display: block;
  object-fit: contain;
}

/* --- Inner letter (visible after opening) / 内部信纸（开启后可见） --- */
.envelope-letter {
  position: absolute;
  top: 10px;
  left: 10px;
  right: 10px;
  bottom: 10px;
  background: linear-gradient(180deg, #FFF8F0 0%, #FFF0E8 100%);
  border-radius: 3px;
  z-index: 1;
  opacity: 0;
  -webkit-transform: translateZ(0);
  transform: translateZ(0);
}

/* Letter lines decoration / 信纸横线装饰 */
.envelope-letter::before {
  content: '';
  position: absolute;
  top: 20px;
  left: 15px;
  right: 15px;
  height: 60%;
  background: repeating-linear-gradient(
    180deg,
    transparent,
    transparent 14px,
    rgba(255, 20, 147, 0.15) 14px,
    rgba(255, 20, 147, 0.15) 15px
  );
}

/* Small heart on letter / 信纸上的小爱心 */
.envelope-letter::after {
  content: '\2764';
  position: absolute;
  top: 50%;
  left: 50%;
  -webkit-transform: translate(-50%, -50%);
  transform: translate(-50%, -50%);
  font-size: 24px;
  color: rgba(255, 20, 147, 0.25);
}

/* --- Swipe hint / 滑动提示 --- */
.envelope-hint {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 8px;
  opacity: 1;
  -webkit-transition: opacity 0.4s ease;
  transition: opacity 0.4s ease;
}

.envelope-hint.hidden {
  opacity: 0;
  pointer-events: none;
}

/* Bouncing chevron arrow / 弹跳箭头 */
/* Use a wrapper for bounce translation, inner for rotation to avoid diagonal movement */
/* 使用外层包装做弹跳位移，内层做旋转，避免对角线运动 */
.envelope-hint-arrow {
  -webkit-animation: bounceArrow 1.5s ease-in-out infinite;
  animation: bounceArrow 1.5s ease-in-out infinite;
}

.envelope-hint-arrow::after {
  content: '';
  display: block;
  width: 20px;
  height: 20px;
  border-left: 2px solid var(--pink-soft);
  border-top: 2px solid var(--pink-soft);
  -webkit-transform: rotate(45deg);
  transform: rotate(45deg);
}

@-webkit-keyframes bounceArrow {
  0%, 100% { -webkit-transform: translateY(0); opacity: 1; }
  50%      { -webkit-transform: translateY(-10px); opacity: 0.6; }
}
@keyframes bounceArrow {
  0%, 100% { transform: translateY(0); opacity: 1; }
  50%      { transform: translateY(-10px); opacity: 0.6; }
}

.envelope-hint-text {
  font-size: 13px;
  letter-spacing: 1px;
  color: var(--text-muted);
}

/* ====================================================================
   Animation A: Pull-Out (抽出式)
   ==================================================================== */

/* Step 1: Flap rotates open */
.envelope.anim-pull-out .envelope-flap {
  -webkit-animation: flapOpen 0.6s cubic-bezier(0.4, 0, 0.2, 1) forwards;
  animation: flapOpen 0.6s cubic-bezier(0.4, 0, 0.2, 1) forwards;
}

@-webkit-keyframes flapOpen {
  from { -webkit-transform: rotateX(0deg); }
  to   { -webkit-transform: rotateX(180deg); }
}
@keyframes flapOpen {
  from { transform: rotateX(0deg); }
  to   { transform: rotateX(180deg); }
}

/* Step 1: Seal fades with flap */
.envelope.anim-pull-out .envelope-seal {
  -webkit-animation: sealFade 0.4s ease 0.2s forwards;
  animation: sealFade 0.4s ease 0.2s forwards;
}

@-webkit-keyframes sealFade {
  from { opacity: 1; }
  to   { opacity: 0; }
}
@keyframes sealFade {
  from { opacity: 1; }
  to   { opacity: 0; }
}

/* Step 2: Letter slides up from inside */
.envelope.anim-pull-out .envelope-letter {
  -webkit-animation: letterSlideUp 1s cubic-bezier(0.25, 0.46, 0.45, 0.94) 0.5s forwards;
  animation: letterSlideUp 1s cubic-bezier(0.25, 0.46, 0.45, 0.94) 0.5s forwards;
}

@-webkit-keyframes letterSlideUp {
  0%   { opacity: 1; -webkit-transform: translateY(0); }
  100% { opacity: 1; -webkit-transform: translateY(-120%); }
}
@keyframes letterSlideUp {
  0%   { opacity: 1; transform: translateY(0); }
  100% { opacity: 1; transform: translateY(-120%); }
}

/* Step 3: Entire envelope fades out */
.envelope.anim-pull-out.fade-out {
  -webkit-animation: envelopeFadeOut 0.5s ease forwards;
  animation: envelopeFadeOut 0.5s ease forwards;
}

@-webkit-keyframes envelopeFadeOut {
  from { opacity: 1; }
  to   { opacity: 0; }
}
@keyframes envelopeFadeOut {
  from { opacity: 1; }
  to   { opacity: 0; }
}

/* ====================================================================
   Animation B: Flip (翻转式)
   ==================================================================== */

/* Flip container needs 3D context */
.envelope.anim-flip-ready {
  -webkit-transform-style: preserve-3d;
  transform-style: preserve-3d;
  -webkit-perspective: 1000px;
  perspective: 1000px;
}

.envelope-flip-inner {
  position: relative;
  width: 100%;
  height: 100%;
  -webkit-transform-style: preserve-3d;
  transform-style: preserve-3d;
  -webkit-transition: transform 1s cubic-bezier(0.4, 0, 0.2, 1);
  transition: transform 1s cubic-bezier(0.4, 0, 0.2, 1);
}

.envelope.anim-flip .envelope-flip-inner {
  -webkit-transform: rotateY(180deg);
  transform: rotateY(180deg);
}

/* Front face (envelope) / 正面（信封） */
.envelope-flip-front {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  -webkit-backface-visibility: hidden;
  backface-visibility: hidden;
}

/* Back face (letter) / 背面（信纸） */
.envelope-flip-back {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  -webkit-backface-visibility: hidden;
  backface-visibility: hidden;
  -webkit-transform: rotateY(180deg);
  transform: rotateY(180deg);
  background: linear-gradient(180deg, #FFF8F0 0%, #FFF0E8 100%);
  border-radius: 6px;
  overflow: hidden;
}

/* Back face letter lines / 背面信纸横线 */
.envelope-flip-back::before {
  content: '';
  position: absolute;
  top: 20px;
  left: 15px;
  right: 15px;
  height: 70%;
  background: repeating-linear-gradient(
    180deg,
    transparent,
    transparent 14px,
    rgba(255, 20, 147, 0.15) 14px,
    rgba(255, 20, 147, 0.15) 15px
  );
}

.envelope-flip-back::after {
  content: '\2764';
  position: absolute;
  top: 50%;
  left: 50%;
  -webkit-transform: translate(-50%, -50%);
  transform: translate(-50%, -50%);
  font-size: 32px;
  color: rgba(255, 20, 147, 0.25);
}

/* Flip fade out after complete / 翻转完成后淡出 */
.envelope.anim-flip.fade-out {
  -webkit-animation: envelopeFadeOut 0.5s ease forwards;
  animation: envelopeFadeOut 0.5s ease forwards;
}

/* 2D fallback for old browsers (no preserve-3d) / 旧浏览器2D降级 */
.is-low-end .envelope-flip-inner,
.no-preserve-3d .envelope-flip-inner {
  -webkit-transform-style: flat;
  transform-style: flat;
}

.is-low-end .envelope.anim-flip .envelope-flip-inner,
.no-preserve-3d .envelope.anim-flip .envelope-flip-inner {
  -webkit-transform: none;
  transform: none;
  -webkit-animation: flatFlipFallback 1s ease forwards;
  animation: flatFlipFallback 1s ease forwards;
}

@-webkit-keyframes flatFlipFallback {
  0%   { opacity: 1; -webkit-transform: scaleX(1); }
  50%  { opacity: 0; -webkit-transform: scaleX(0); }
  100% { opacity: 0; -webkit-transform: scaleX(0); }
}
@keyframes flatFlipFallback {
  0%   { opacity: 1; transform: scaleX(1); }
  50%  { opacity: 0; transform: scaleX(0); }
  100% { opacity: 0; transform: scaleX(0); }
}

/* ====================================================================
   Animation C: Scatter (飘散式)
   ==================================================================== */

/* Scatter fragment / 飘散碎片 */
.scatter-fragment {
  position: absolute;
  background: linear-gradient(145deg, #1A0A14 0%, #2D0A24 100%);
  border: 1px solid rgba(255, 20, 147, 0.1);
  opacity: 1;
  -webkit-transform: translateZ(0);
  transform: translateZ(0);
  will-change: transform, opacity;
}

.scatter-fragment.animating {
  -webkit-animation: scatterPiece 1.5s cubic-bezier(0.25, 0.46, 0.45, 0.94) forwards;
  animation: scatterPiece 1.5s cubic-bezier(0.25, 0.46, 0.45, 0.94) forwards;
  -webkit-animation-delay: var(--scatter-delay, 0s);
  animation-delay: var(--scatter-delay, 0s);
}

@-webkit-keyframes scatterPiece {
  0% {
    -webkit-transform: translate(0, 0) rotate(0deg);
    opacity: 1;
  }
  100% {
    -webkit-transform: translate(var(--scatter-x, 0px), var(--scatter-y, 0px)) rotate(var(--scatter-rotate, 0deg));
    opacity: 0;
  }
}
@keyframes scatterPiece {
  0% {
    transform: translate(0, 0) rotate(0deg);
    opacity: 1;
  }
  100% {
    transform: translate(var(--scatter-x, 0px), var(--scatter-y, 0px)) rotate(var(--scatter-rotate, 0deg));
    opacity: 0;
  }
}

/* Scatter letter reveal / 飘散后信纸显现 */
.scatter-letter {
  position: absolute;
  top: 50%;
  left: 50%;
  width: 260px;
  height: 180px;
  -webkit-transform: translate(-50%, -50%) translateZ(0);
  transform: translate(-50%, -50%) translateZ(0);
  background: linear-gradient(180deg, #FFF8F0 0%, #FFF0E8 100%);
  border-radius: 6px;
  opacity: 0;
  pointer-events: none;
}

.scatter-letter.visible {
  -webkit-animation: scatterLetterReveal 0.8s ease 0.8s forwards;
  animation: scatterLetterReveal 0.8s ease 0.8s forwards;
}

@-webkit-keyframes scatterLetterReveal {
  from { opacity: 0; -webkit-transform: translate(-50%, -50%) scale(0.8); }
  to   { opacity: 1; -webkit-transform: translate(-50%, -50%) scale(1); }
}
@keyframes scatterLetterReveal {
  from { opacity: 0; transform: translate(-50%, -50%) scale(0.8); }
  to   { opacity: 1; transform: translate(-50%, -50%) scale(1); }
}

/* Scatter letter lines / 飘散信纸横线 */
.scatter-letter::before {
  content: '';
  position: absolute;
  top: 20px;
  left: 15px;
  right: 15px;
  height: 70%;
  background: repeating-linear-gradient(
    180deg,
    transparent,
    transparent 14px,
    rgba(255, 20, 147, 0.15) 14px,
    rgba(255, 20, 147, 0.15) 15px
  );
}

.scatter-letter::after {
  content: '\2764';
  position: absolute;
  top: 50%;
  left: 50%;
  -webkit-transform: translate(-50%, -50%);
  transform: translate(-50%, -50%);
  font-size: 28px;
  color: rgba(255, 20, 147, 0.25);
}

/* ====================================================================
   Envelope follow-finger effect / 信封跟随手指效果
   ==================================================================== */
.envelope-wrapper.dragging .envelope {
  -webkit-transition: transform 0.05s linear;
  transition: transform 0.05s linear;
}

/* ====================================================================
   Fade out entire envelope screen / 整个信封屏幕淡出
   ==================================================================== */
#envelope-screen.fade-out {
  -webkit-animation: fadeOutScreen 0.6s ease forwards;
  animation: fadeOutScreen 0.6s ease forwards;
}

@-webkit-keyframes fadeOutScreen {
  from { opacity: 1; }
  to   { opacity: 0; }
}
@keyframes fadeOutScreen {
  from { opacity: 1; }
  to   { opacity: 0; }
}

/* ====================================================================
   Responsive adjustments / 响应式调整
   ==================================================================== */

/* Small mobile / 小型手机 */
@media (max-width: 360px) {
  .envelope {
    width: 240px;
    height: 170px;
  }
  .envelope-flap {
    height: 68px;
    -webkit-clip-path: polygon(0 0, 50% 68px, 100% 0);
    clip-path: polygon(0 0, 50% 68px, 100% 0);
  }
  .envelope-seal {
    top: 30px;
    width: 36px;
    height: 36px;
  }
  .envelope-text {
    font-size: 15px;
    bottom: 24px;
  }
  .scatter-letter {
    width: 220px;
    height: 150px;
  }
}

/* Tablet and desktop / 平板和桌面 */
@media (min-width: 768px) {
  .envelope {
    width: 360px;
    height: 260px;
  }
  .envelope-flap {
    height: 104px;
    -webkit-clip-path: polygon(0 0, 50% 104px, 100% 0);
    clip-path: polygon(0 0, 50% 104px, 100% 0);
  }
  .envelope-seal {
    top: 50px;
    width: 48px;
    height: 48px;
  }
  .envelope-seal::after {
    font-size: 20px;
  }
  .envelope-text {
    font-size: 22px;
    bottom: 40px;
  }
  .scatter-letter {
    width: 340px;
    height: 240px;
  }
}

/* Large desktop / 大型桌面 */
@media (min-width: 1200px) {
  .envelope {
    width: 420px;
    height: 300px;
  }
  .envelope-flap {
    height: 120px;
    -webkit-clip-path: polygon(0 0, 50% 120px, 100% 0);
    clip-path: polygon(0 0, 50% 120px, 100% 0);
  }
  .envelope-seal {
    top: 58px;
    width: 52px;
    height: 52px;
  }
  .envelope-text {
    font-size: 24px;
    bottom: 48px;
  }
}