/* =========================================================
   TIDE LETTERS · FX 层
   ---------------------------------------------------------
   1  氛围画布 / 颗粒 / 暗角
   2  页面淡入 · 站内转场 · View Transitions
   3  [data-reveal] 入场 / [data-split] 逐字
   4  滚动提示 scroll-cue
   5  自定义光标
   6  开场信 fx-intro
   7  降级：reduced-motion / 触屏 / 低性能
   —— 颜色只用 tokens.css 的变量，不写死色值
   ========================================================= */

/* =========================================================
   1 · 氛围画布
   ========================================================= */
#fx-ambient {
  opacity: 1;
  transition: opacity 1.1s var(--ease);
  /* 把氛围压向上下边缘：首屏完整，越往下越融进纸里 */
  -webkit-mask-image: linear-gradient(180deg,
      #000 0%, #000 56%,
      rgba(0, 0, 0, .92) 72%,
      rgba(0, 0, 0, .48) 88%,
      transparent 100%);
  mask-image: linear-gradient(180deg,
      #000 0%, #000 56%,
      rgba(0, 0, 0, .92) 72%,
      rgba(0, 0, 0, .48) 88%,
      transparent 100%);
  will-change: opacity;
}
#fx-ambient canvas { position: absolute; inset: 0; }
.fx-ambient__canvas { pointer-events: none; }
.fx-ambient__sky { z-index: 0; }
.fx-ambient__sea { z-index: 1; }
.fx-ambient__dust { z-index: 2; }

/* 翻过首屏后整层氛围退到背景里，正文不被打扰 */
:root.fx-past-hero #fx-ambient { opacity: .3; }
/* 开场信打开时，海面停一停，把注意力留给那封信 */
:root.fx-intro-open #fx-ambient { opacity: .5; }

/* 正文页：海只留在页头，往下化进纸里，不压正文 */
body[data-page="about"] #fx-ambient,
body[data-page="poems"] #fx-ambient,
body[data-page="poem"] #fx-ambient,
body[data-page="collections"] #fx-ambient,
body[data-page="timeline"] #fx-ambient,
body[data-page="studio"] #fx-ambient,
body[data-page="play"] #fx-ambient,
body[data-page="me"] #fx-ambient {
  opacity: .8;
  -webkit-mask-image: linear-gradient(180deg,
      #000 0%, #000 22%,
      rgba(0, 0, 0, .55) 42%,
      rgba(0, 0, 0, .2) 56%,
      transparent 68%);
  mask-image: linear-gradient(180deg,
      #000 0%, #000 22%,
      rgba(0, 0, 0, .55) 42%,
      rgba(0, 0, 0, .2) 56%,
      transparent 68%);
}
:root.fx-past-hero body[data-page="about"] #fx-ambient { opacity: .22; }

/* 暗角：压一压边角就够了，别把正文染灰 */
#fx-grain::after { opacity: .5; }
:root[data-mode="paper"] #fx-grain::after { opacity: .4; }

/* 颗粒：极慢的明暗呼吸（只动 opacity，交给合成器） */
#fx-grain {
  animation: fx-grain-breathe 34s var(--ease) infinite alternate;
}
@keyframes fx-grain-breathe {
  from { opacity: var(--grain-opacity); }
  to { opacity: calc(var(--grain-opacity) * 1.5); }
}

/* =========================================================
   2 · 页面淡入 / 站内转场
   ========================================================= */
@keyframes fx-page-in {
  from { opacity: 0; }
  to { opacity: 1; }
}
/* 支持跨文档 View Transitions 的浏览器用它，别让两层动效叠加 */
@supports not (view-transition-name: root) {
  body { animation: fx-page-in 520ms var(--ease-out) both; }
}

@view-transition { navigation: auto; }
::view-transition-old(root) {
  animation: fx-vt-out 180ms var(--ease) both;
}
::view-transition-new(root) {
  animation: fx-vt-in 420ms var(--ease-out) both;
}
@keyframes fx-vt-out { to { opacity: 0; } }
@keyframes fx-vt-in { from { opacity: 0; } to { opacity: 1; } }

/* 不支持 View Transitions 时的 180ms 淡出遮罩 */
.fx-transition {
  position: fixed; inset: 0; z-index: 9999;
  background:
    radial-gradient(120% 80% at 50% 0%, color-mix(in srgb, var(--glow) 45%, transparent), transparent 60%),
    var(--bg);
  opacity: 0; visibility: hidden; pointer-events: none;
  transition: opacity 180ms var(--ease), visibility 180ms;
}
.fx-transition.is-out { opacity: 1; visibility: visible; pointer-events: auto; }

/* =========================================================
   3 · 入场：reveal / split
   —— 用 scripting 查询兜底：完全禁 JS 时内容直接可见
   ========================================================= */
@media (scripting: enabled) {
  [data-reveal] {
    opacity: 0;
    transform: translate3d(0, 26px, 0);
    transition:
      opacity 880ms var(--ease-out),
      transform 980ms var(--ease-out);
    transition-delay: calc(var(--reveal-delay, 0) * 90ms);
    will-change: opacity, transform;
  }
  [data-reveal].is-in {
    opacity: 1;
    transform: none;
    will-change: auto;
  }
  [data-reveal="fade"] { transform: none; }
  [data-reveal="fade"].is-in { transform: none; }
  [data-reveal="line"] {
    opacity: 1;
    transform: none;
    position: relative;
  }
  [data-reveal="line"]::after {
    content: "";
    position: absolute; left: 0; right: 0; bottom: -10px; height: 1px;
    background: linear-gradient(90deg, var(--accent), var(--line-2) 60%, transparent);
    transform: scaleX(0); transform-origin: left center;
    transition: transform 1200ms var(--ease-out);
    transition-delay: calc(var(--reveal-delay, 0) * 90ms);
  }
  [data-reveal="line"].is-in::after { transform: scaleX(1); }
}

/* data-delay="1..6" 阶梯（不写 var 也成立） */
[data-delay="0"] { --reveal-delay: 0; }
[data-delay="1"] { --reveal-delay: 1; }
[data-delay="2"] { --reveal-delay: 2; }
[data-delay="3"] { --reveal-delay: 3; }
[data-delay="4"] { --reveal-delay: 4; }
[data-delay="5"] { --reveal-delay: 5; }
[data-delay="6"] { --reveal-delay: 6; }
[data-delay="7"] { --reveal-delay: 7; }
[data-delay="8"] { --reveal-delay: 8; }

/* 逐字入场：motion.js 拆成 .split-word > .split-char */
[data-split] { text-wrap: balance; }
.split-word {
  display: inline-block;
  white-space: nowrap;
  /* 让逐字块不触发额外的行内基线抖动 */
  vertical-align: baseline;
}
.split-char {
  display: inline-block;
  opacity: 0;
  transform: translate3d(0, .58em, 0) rotate(1.5deg);
  transition:
    opacity 820ms var(--ease-out),
    transform 1060ms var(--ease-out);
  transition-delay: calc(min(var(--ci, 0), 42) * 34ms);
  will-change: opacity, transform;
}
[data-split].is-in .split-char {
  opacity: 1;
  transform: none;
}
[data-split].is-in .split-char { will-change: auto; }

/* =========================================================
   4 · 滚动提示
   ========================================================= */
.scroll-cue {
  position: relative;
  display: inline-flex;
  flex-direction: column;
  align-items: center;
  gap: 12px;
  padding: 10px 12px 8px;
  color: var(--ink-3);
  font-size: 10.5px;
  letter-spacing: .3em;
  text-transform: uppercase;
  font-family: var(--font-display);
  transition: color var(--dur-mid) var(--ease);
  animation: cue-in 1.1s 1s var(--ease-out) both;
}
.scroll-cue:hover { color: var(--accent); }
.scroll-cue__text { padding-left: .3em; }
.scroll-cue__line {
  position: relative;
  display: block;
  width: 1px; height: 54px;
  background: linear-gradient(180deg, var(--line-2), transparent);
  overflow: hidden;
}
.scroll-cue__line::after {
  content: "";
  position: absolute; left: 0; top: 0;
  width: 1px; height: 16px;
  background: linear-gradient(180deg, transparent, var(--accent));
  animation: cue-drop 2.8s var(--ease) infinite;
}
.scroll-cue--fixed {
  position: fixed;
  left: 50%; bottom: clamp(18px, 3.5vh, 40px);
  transform: translateX(-50%);
  z-index: calc(var(--z-content) + 1);
  pointer-events: auto;
}
@keyframes cue-in {
  from { opacity: 0; transform: translateY(-6px); }
  to { opacity: 1; transform: none; }
}
@keyframes cue-drop {
  0% { transform: translateY(-18px); opacity: 0; }
  22% { opacity: .9; }
  70% { opacity: .9; }
  100% { transform: translateY(58px); opacity: 0; }
}
.fx-intro-open .scroll-cue { opacity: 0 !important; }

/* =========================================================
   5 · 自定义光标
   ========================================================= */
html.has-custom-cursor,
html.has-custom-cursor * { cursor: none !important; }
/* 文本输入处恢复原生光标 */
html.has-custom-cursor.fx-native-cursor,
html.has-custom-cursor.fx-native-cursor * { cursor: auto !important; }
html.has-custom-cursor.fx-native-cursor input,
html.has-custom-cursor.fx-native-cursor textarea,
html.has-custom-cursor.fx-native-cursor [contenteditable] { cursor: text !important; }

.fx-cursor {
  position: fixed; top: 0; left: 0;
  z-index: var(--z-cursor);
  width: 0; height: 0;
  pointer-events: none;
  contain: layout style;
}
.fx-cursor__ring {
  position: absolute; left: 0; top: 0;
  width: 30px; height: 30px;
  margin: -15px 0 0 -15px;
  border: 1px solid color-mix(in srgb, var(--ink) 44%, transparent);
  border-radius: 50%;
  background: transparent;
  opacity: 0;
  transform: scale(.55);
  transition:
    opacity 340ms var(--ease),
    transform 420ms var(--ease-out),
    border-color 320ms var(--ease),
    background-color 320ms var(--ease);
}
.fx-cursor__dot {
  position: absolute; left: 0; top: 0;
  width: 4px; height: 4px;
  margin: -2px 0 0 -2px;
  border-radius: 50%;
  background: var(--accent);
  opacity: 0;
  transition: opacity 260ms var(--ease), transform 260ms var(--ease);
}
.fx-cursor__label {
  position: absolute; left: 0; top: 0;
  white-space: nowrap;
  font-family: var(--font-serif);
  font-size: 11px;
  letter-spacing: .2em;
  color: var(--accent-2);
  opacity: 0;
  transition: opacity 260ms var(--ease);
}
.fx-cursor.is-visible .fx-cursor__ring {
  opacity: .65;
  transform: scale(1);
}
.fx-cursor.is-visible .fx-cursor__dot { opacity: .8; }
.fx-cursor.is-visible.has-label .fx-cursor__label { opacity: .95; }
.fx-cursor.is-hover .fx-cursor__ring {
  transform: scale(1.8);
  opacity: .95;
  border-color: color-mix(in srgb, var(--accent) 72%, transparent);
  background-color: color-mix(in srgb, var(--accent) 7%, transparent);
}
.fx-cursor.is-hover .fx-cursor__dot { opacity: 0; transform: scale(.4); }
.fx-cursor.is-down .fx-cursor__ring { transform: scale(1.42); }
.fx-cursor.is-hidden .fx-cursor__ring,
.fx-cursor.is-hidden .fx-cursor__dot { opacity: 0; }
.fx-cursor__ring::after {
  content: "";
  position: absolute; inset: 7px;
  border-radius: 50%;
  border: 1px solid color-mix(in srgb, var(--ink) 20%, transparent);
  opacity: 0;
  transition: opacity 300ms var(--ease);
}
.fx-cursor.is-hover .fx-cursor__ring::after { opacity: .9; }

/* =========================================================
   6 · 开场信 fx-intro
   ---------------------------------------------------------
   场景固定是「夜里的海」：遮罩压暗 + 模糊，前景是暖色信纸。
   信纸不随主题翻转（夜里拆开的信，纸自然是暖的），这是这一屏
   唯一允许的“硬编码材质色”，它属于道具，不属于主题。
   ========================================================= */
.fx-intro {
  --paper: #f8f2e5;
  --paper-2: #f0e6d3;
  --paper-3: #e4d5ba;
  --paper-ink: #222f3e;
  --paper-ink-2: #5d6976;
  --paper-line: rgba(52, 63, 76, .2);
  --paper-gold: #b08542;
  position: fixed; inset: 0;
  z-index: calc(var(--z-modal) + 4);
  display: grid;
  place-items: center;
  padding: clamp(20px, 6vh, 64px) var(--sp-5);
  opacity: 0;
  visibility: hidden;
  transition: opacity 560ms var(--ease), visibility 560ms;
  overflow: hidden;
  overscroll-behavior: contain;
}
.fx-intro.is-in { opacity: 1; visibility: visible; }
.fx-intro.is-leaving { opacity: 0; pointer-events: none; }

/* 遮罩：压暗并模糊掉后面的页面，只留一点月光的方向感 */
.fx-intro__veil {
  position: absolute; inset: 0;
  background:
    radial-gradient(80% 60% at 71% 20%, rgba(150, 182, 214, .16), transparent 62%),
    radial-gradient(120% 92% at 18% 104%, rgba(10, 26, 42, .66), transparent 72%),
    linear-gradient(180deg, rgba(8, 16, 28, .66) 0%, rgba(3, 7, 13, .94) 100%);
  -webkit-backdrop-filter: blur(18px) saturate(115%);
  backdrop-filter: blur(18px) saturate(115%);
}

/* 远处的月光与海平线 */
.fx-intro__sky {
  position: absolute; inset: 0;
  pointer-events: none;
  background:
    radial-gradient(42% 30% at 71% 22%, rgba(214, 230, 245, .16), transparent 72%),
    radial-gradient(70% 50% at 16% 6%, rgba(120, 150, 190, .1), transparent 70%);
  opacity: .92;
  animation: intro-sky-breathe 22s var(--ease) infinite alternate;
}
.fx-intro__sky::after {
  content: "";
  position: absolute; left: 0; right: 0; top: 64%;
  height: 1px;
  background: linear-gradient(90deg, transparent, rgba(226, 232, 238, .1) 28%, rgba(226, 232, 238, .2) 52%, rgba(226, 232, 238, .09) 74%, transparent);
  box-shadow: 0 0 22px 3px rgba(200, 216, 232, .08);
}
.fx-intro__moon {
  position: absolute; left: 71%; top: 22%;
  width: clamp(64px, 7.5vw, 104px);
  height: clamp(64px, 7.5vw, 104px);
  margin-left: calc(clamp(64px, 7.5vw, 104px) / -2);
  margin-top: calc(clamp(64px, 7.5vw, 104px) / -2);
  border-radius: 50%;
  background:
    radial-gradient(circle,
      rgba(255, 253, 246, 1) 0%,
      rgba(255, 253, 246, 1) 24%,
      rgba(246, 246, 240, .92) 30%,
      rgba(220, 232, 242, .3) 44%,
      rgba(200, 218, 235, .1) 58%,
      transparent 72%);
  box-shadow: 0 0 40px 10px rgba(215, 228, 242, .12);
  filter: blur(.2px);
  animation: intro-moon-breathe 12s var(--ease) infinite alternate;
}
@keyframes intro-sky-breathe {
  from { opacity: .74; transform: scale(1); }
  to { opacity: 1; transform: scale(1.03); }
}
@keyframes intro-moon-breathe {
  from { opacity: .8; transform: scale(.985); }
  to { opacity: 1; transform: scale(1.02); }
}

/* ---------- 信封 ---------- */
.fx-intro__stage {
  position: relative;
  display: flex; flex-direction: column; align-items: center;
  transition: opacity 620ms var(--ease), transform 720ms var(--ease);
}
/* 信封与信纸占同一个格位，切换时原地叠化 */
.fx-intro__stage,
.fx-intro__sheet { grid-area: 1 / 1; }
.fx-intro.is-letter .fx-intro__stage {
  opacity: 0;
  transform: translateY(-3vh) scale(.96);
  pointer-events: none;
}

.fx-intro__envelope {
  position: relative;
  width: clamp(282px, 34vw, 408px);
  aspect-ratio: 1.5;
  perspective: 1500px;
  cursor: pointer;
  animation: env-float 9s var(--ease) infinite alternate;
  transition: transform 900ms var(--ease-out);
}
@keyframes env-float {
  from { transform: translateY(6px) rotate(-.3deg); }
  to { transform: translateY(-8px) rotate(.3deg); }
}
.fx-intro.is-open .fx-intro__envelope { animation-play-state: paused; }
/* 信封上压一行小字，像寄信人留下的地址 */
.fx-intro__envelope::before {
  content: "潮汐书信 · TIDE LETTERS";
  position: absolute; left: 9%; bottom: 7%;
  z-index: 5;
  font-family: var(--font-display);
  font-size: clamp(7px, .78vw, 9px);
  letter-spacing: .26em;
  color: rgba(118, 96, 62, .4);
  pointer-events: none;
}
/* 信落在海面/桌面上的那一点影子 */
.fx-intro__envelope::after {
  content: "";
  position: absolute; left: 5%; right: 5%; bottom: -14%; height: 18%;
  z-index: -1;
  background: radial-gradient(50% 50% at 50% 50%, rgba(0, 0, 0, .62), transparent 72%);
  filter: blur(8px);
}
.fx-intro__env { position: absolute; inset: 0; transform-style: preserve-3d; }

/* 信封纸 */
.fx-intro__env-back {
  position: absolute; inset: 0;
  border-radius: 3px;
  border: 1px solid rgba(118, 96, 62, .34);
  background:
    linear-gradient(150deg, rgba(255, 255, 255, .5), transparent 46%),
    linear-gradient(165deg, var(--paper) 0%, var(--paper-2) 68%, var(--paper-3) 100%);
  box-shadow:
    0 30px 64px -26px rgba(0, 0, 0, .68),
    inset 0 0 0 1px rgba(255, 255, 255, .32);
}
.fx-intro__env-back::before {
  content: "";
  position: absolute; inset: 0; border-radius: inherit;
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='180' height='180'%3E%3Cfilter id='n'%3E%3CfeTurbulence type='fractalNoise' baseFrequency='.82' numOctaves='3'/%3E%3C/filter%3E%3Crect width='100%25' height='100%25' filter='url(%23n)'/%3E%3C/svg%3E");
  opacity: .055;
  mix-blend-mode: multiply;
  pointer-events: none;
}

/* 信纸从信封里探出的一角 */
.fx-intro__peek {
  position: absolute; left: 5.5%; right: 5.5%; top: 6%; bottom: 8%;
  border-radius: 2px;
  border: 1px solid rgba(118, 96, 62, .24);
  background:
    repeating-linear-gradient(180deg, transparent 0 20px, rgba(70, 60, 45, .07) 20px 21px),
    linear-gradient(180deg, #fdfaf2 0%, var(--paper) 100%);
  box-shadow: 0 -3px 10px rgba(0, 0, 0, .18);
  transform: translateY(4%) scale(.98);
  transition: transform 820ms var(--ease-out) 120ms;
  z-index: 2;
}
.fx-intro.is-open .fx-intro__peek {
  transform: translateY(-26%) scale(.985);
}

/* 信封口袋：上缘是 V 字 */
.fx-intro__env-front {
  position: absolute; inset: 0;
  border-radius: 3px;
  clip-path: polygon(0 0, 50% 43%, 100% 0, 100% 100%, 0 100%);
  background:
    linear-gradient(180deg,
      color-mix(in srgb, var(--paper-2) 72%, #fff) 0%,
      var(--paper-2) 42%,
      var(--paper-3) 100%);
  /* drop-shadow 跟着 clip-path 的形状走，正好替 V 字压一道折痕 */
  filter: drop-shadow(0 -1px 0 rgba(118, 96, 62, .5)) drop-shadow(0 -9px 14px rgba(70, 54, 30, .16));
  z-index: 3;
}
.fx-intro__env-front::before {
  content: "";
  position: absolute; inset: 0;
  clip-path: inherit;
  background:
    linear-gradient(47deg, transparent 49.7%, rgba(118, 96, 62, .14) 49.85%, transparent 50%),
    linear-gradient(-47deg, transparent 49.7%, rgba(118, 96, 62, .14) 49.85%, transparent 50%);
  opacity: .9;
}
.fx-intro__env-front::after {
  content: "";
  position: absolute; inset: 0;
  clip-path: inherit;
  background: linear-gradient(180deg, rgba(255, 255, 255, .22), transparent 34%);
}

/* 封口三角 */
.fx-intro__env-flap {
  position: absolute; left: 0; right: 0; top: 0;
  height: 44%;
  clip-path: polygon(0 0, 100% 0, 50% 100%);
  background: linear-gradient(178deg,
    color-mix(in srgb, var(--paper) 82%, #fff) 0%,
    color-mix(in srgb, var(--paper) 72%, #ecd9b6) 34%,
    color-mix(in srgb, var(--paper-2) 78%, #e6d2ab) 72%,
    color-mix(in srgb, var(--paper-3) 92%, #cdb388) 100%);
  transform-origin: top center;
  transition: transform 860ms var(--ease-out), opacity 440ms 300ms, z-index 0s linear 340ms;
  z-index: 4;
  backface-visibility: hidden;
  filter: drop-shadow(0 0 1.2px rgba(74, 55, 28, .6)) drop-shadow(0 5px 7px rgba(74, 55, 28, .3));
}
.fx-intro.is-open .fx-intro__env-flap {
  transform: rotateX(-178deg);
  z-index: 1;
  opacity: 0;
}

/* 火漆印：金色圆 + 浮雕「鱿」 */
.fx-intro__seal {
  position: absolute; left: 50%; top: 44%;
  width: 17.5%; aspect-ratio: 1;
  transform: translate(-50%, -50%);
  border-radius: 50%;
  display: grid; place-items: center;
  background:
    radial-gradient(circle at 35% 28%,
      #e2bd7d 0%, #c3944c 38%, #a97c38 62%, #8a6329 84%, #7a5522 100%);
  box-shadow:
    0 10px 24px -8px rgba(0, 0, 0, .75),
    inset 0 1px 1px rgba(255, 246, 224, .55),
    inset 0 -2px 5px rgba(74, 48, 12, .55),
    inset 0 0 0 3px rgba(255, 244, 220, .12);
  z-index: 6;
  transition: transform 540ms var(--ease-out), opacity 380ms var(--ease);
}
.fx-intro__seal::before {
  content: "";
  position: absolute; inset: 11%;
  border-radius: 50%;
  border: 1px solid rgba(90, 60, 20, .5);
  box-shadow: inset 0 1px 2px rgba(255, 250, 235, .3);
}
.fx-intro__seal span {
  position: relative;
  font-family: var(--font-serif);
  font-size: clamp(14px, 1.8vw, 21px);
  line-height: 1;
  color: #f8eed8;
  text-shadow: 0 1px 1px rgba(80, 50, 10, .7), 0 -1px 1px rgba(255, 240, 210, .22);
  transform: translateY(-1px);
}
.fx-intro.is-open .fx-intro__seal {
  transform: translate(-50%, -50%) scale(1.3) rotate(-10deg);
  opacity: 0;
}

/* 邮票 */
.fx-intro__stamp {
  position: absolute; right: -5.5%; top: -8.5%;
  width: 18%; aspect-ratio: .8;
  transform: rotate(7deg);
  display: flex; flex-direction: column; align-items: center; justify-content: center; gap: 2px;
  border: 1px dashed rgba(150, 118, 62, .55);
  background:
    linear-gradient(160deg, rgba(255, 255, 255, .6), transparent 55%),
    var(--paper-2);
  color: rgba(126, 92, 40, .92);
  font-family: var(--font-display);
  font-size: clamp(6px, .72vw, 8.5px);
  letter-spacing: .16em;
  line-height: 1.25;
  box-shadow:
    0 8px 18px -10px rgba(0, 0, 0, .5),
    inset 0 0 0 3px rgba(255, 252, 244, .75),
    inset 0 0 0 4px rgba(150, 118, 62, .18);
  opacity: .92;
  transition: opacity 400ms var(--ease), transform 700ms var(--ease);
  animation: stamp-in 1s 1.15s var(--ease-out) both;
}
.fx-intro__stamp::after {
  content: "";
  position: absolute; inset: 38% 16% auto;
  height: 1px;
  background: rgba(150, 118, 62, .4);
}
@keyframes stamp-in {
  from { opacity: 0; transform: rotate(16deg) translateY(6px) scale(1.1); }
  to { opacity: .92; transform: rotate(7deg); }
}

/* 提示 */
.fx-intro__hint {
  margin-top: clamp(24px, 4vh, 40px);
  font-family: var(--font-serif);
  font-size: clamp(12.5px, 1.1vw, 14px);
  letter-spacing: .34em;
  padding-left: .34em;
  color: rgba(238, 232, 219, .72);
  animation: hint-breathe 3.6s var(--ease) infinite alternate;
  transition: opacity 400ms var(--ease), color 400ms var(--ease);
}
.fx-intro.is-impatient .fx-intro__hint {
  color: rgba(230, 196, 132, .92);
  animation-duration: 1.6s;
}
@keyframes hint-breathe {
  from { opacity: .45; }
  to { opacity: .95; }
}
.fx-intro.is-letter .fx-intro__hint,
.fx-intro.is-open .fx-intro__hint { opacity: 0; }

/* 跳过 */
.fx-intro__skip {
  position: absolute;
  top: clamp(16px, 3.5vh, 34px); right: clamp(16px, 3vw, 40px);
  z-index: 10;
  min-height: 40px;
  padding: 0 18px;
  display: inline-flex; align-items: center;
  border: 1px solid rgba(238, 232, 219, .26);
  border-radius: var(--r-full);
  color: rgba(238, 232, 219, .74);
  font-size: var(--fs-xs);
  letter-spacing: .2em;
  background: rgba(10, 18, 28, .32);
  -webkit-backdrop-filter: blur(8px);
  backdrop-filter: blur(8px);
  transition: color var(--dur-mic) var(--ease), border-color var(--dur-mic) var(--ease),
              background var(--dur-mic) var(--ease);
  animation: fade-down 900ms 1.4s var(--ease-out) both;
}
.fx-intro__skip:hover {
  color: rgba(252, 248, 238, .98);
  border-color: rgba(226, 199, 152, .7);
  background: rgba(18, 30, 44, .5);
}
@keyframes fade-down {
  from { opacity: 0; transform: translateY(-8px); }
  to { opacity: 1; transform: none; }
}
.fx-intro__foot {
  position: absolute;
  left: 0; right: 0; bottom: clamp(14px, 3vh, 28px);
  text-align: center;
  font-size: 10px;
  letter-spacing: .26em;
  color: rgba(214, 210, 200, .5);
  transition: opacity 400ms var(--ease);
}
.fx-intro.is-letter .fx-intro__foot { opacity: .42; }

/* ---------- 信纸 ---------- */
.fx-intro__sheet {
  position: relative;
  z-index: 5;
  display: grid;
  place-items: center;
  width: 100%;
  max-height: 100%;
  opacity: 0;
  visibility: hidden;
  transform: translateY(22px) scale(.985);
  transition: opacity 780ms var(--ease-out), transform 900ms var(--ease-out), visibility 0s linear 780ms;
  pointer-events: none;
}
.fx-intro.is-letter .fx-intro__sheet {
  opacity: 1;
  visibility: visible;
  transform: none;
  transition-delay: 100ms, 100ms, 0s;
  pointer-events: auto;
}

.fx-intro__paper {
  position: relative;
  width: min(556px, 100%);
  max-height: min(80vh, 760px);
  overflow: auto;
  padding: clamp(30px, 4.4vw, 56px) clamp(24px, 4vw, 48px) clamp(24px, 3.2vw, 38px);
  border-radius: 2px;
  border: 1px solid rgba(118, 96, 62, .38);
  color: var(--paper-ink);
  background:
    radial-gradient(120% 66% at 50% -10%, rgba(255, 253, 246, .92), transparent 62%),
    repeating-linear-gradient(180deg, transparent 0 31px, rgba(96, 80, 55, .045) 31px 32px),
    linear-gradient(178deg, var(--paper) 0%, var(--paper-2) 64%, var(--paper-3) 100%);
  box-shadow:
    0 44px 110px -42px rgba(0, 0, 0, .82),
    inset 0 1px 0 rgba(255, 255, 255, .55),
    inset 0 0 0 1px rgba(255, 255, 255, .22);
  transform: rotate(-.35deg);
  animation: paper-in 900ms 120ms var(--ease-out) both;
  scrollbar-width: thin;
}
@keyframes paper-in {
  from { opacity: 0; transform: translateY(26px) rotate(-.35deg) scale(.985); }
  to { opacity: 1; transform: translateY(0) rotate(-.35deg) scale(1); }
}
/* 纸纤维 + 内框 */
.fx-intro__paper::before {
  content: "";
  position: absolute; inset: 0;
  pointer-events: none;
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='180' height='180'%3E%3Cfilter id='n'%3E%3CfeTurbulence type='fractalNoise' baseFrequency='.82' numOctaves='3'/%3E%3C/filter%3E%3Crect width='100%25' height='100%25' filter='url(%23n)'/%3E%3C/svg%3E");
  opacity: .06;
  mix-blend-mode: multiply;
}
.fx-intro__paper::after {
  content: "";
  position: absolute;
  inset: 11px;
  pointer-events: none;
  border: 1px solid rgba(118, 96, 62, .24);
  border-radius: 1px;
}

.fx-intro__paper > * {
  position: relative;
  z-index: 1;
  opacity: 0;
  transform: translateY(13px);
  transition: opacity 760ms var(--ease-out), transform 860ms var(--ease-out);
}
.fx-intro.is-letter .fx-intro__paper > * { opacity: 1; transform: none; }
.fx-intro__paper > *:nth-child(1) { transition-delay: 220ms; }
.fx-intro__paper > *:nth-child(2) { transition-delay: 300ms; }
.fx-intro__paper > *:nth-child(3) { transition-delay: 380ms; }
.fx-intro__paper > *:nth-child(4) { transition-delay: 460ms; }
.fx-intro__paper > *:nth-child(5) { transition-delay: 560ms; }
.fx-intro__paper > *:nth-child(6) { transition-delay: 660ms; }
.fx-intro__paper > *:nth-child(7) { transition-delay: 780ms; }
.fx-intro__paper > *:nth-child(8) { transition-delay: 900ms; }
.fx-intro__paper > *:nth-child(9) { transition-delay: 1020ms; }

.fx-intro__eyebrow {
  font-family: var(--font-display);
  font-size: 10px;
  letter-spacing: .34em;
  color: var(--paper-ink-2);
  text-align: center;
  text-transform: uppercase;
}
.fx-intro__kicker {
  margin-top: clamp(18px, 2.4vw, 26px);
  font-family: var(--font-serif);
  font-size: var(--fs-xs);
  letter-spacing: .3em;
  color: var(--paper-ink-2);
  text-align: center;
}
.fx-intro__title {
  margin-top: 10px;
  font-family: var(--font-serif);
  font-weight: 400;
  font-size: clamp(30px, 4.6vw, 42px);
  letter-spacing: .28em;
  padding-left: .28em;
  line-height: 1.3;
  text-align: center;
  color: var(--paper-ink);
}
.fx-intro__rule {
  width: 56px; height: 1px;
  margin: clamp(20px, 2.8vw, 30px) auto;
  background: linear-gradient(90deg, transparent, var(--paper-gold), transparent);
  opacity: .85;
}
.fx-intro__quote {
  font-family: var(--font-serif);
  font-size: clamp(17px, 2vw, 21px);
  line-height: 2.06;
  letter-spacing: .07em;
  text-align: center;
  color: var(--paper-ink);
  max-width: 24em;
  margin: 0 auto;
  text-wrap: balance;
}
.fx-intro__from {
  margin-top: clamp(16px, 2vw, 22px);
  font-family: var(--font-serif);
  font-style: italic;
  font-size: var(--fs-sm);
  letter-spacing: .08em;
  color: var(--paper-ink-2);
  text-align: center;
}
.fx-intro__actions {
  display: flex;
  justify-content: center;
  align-items: center;
  flex-wrap: wrap;
  gap: var(--sp-3);
  margin-top: clamp(24px, 3.4vw, 36px);
}
.fx-intro__paper .btn--primary {
  --btn-bg: var(--paper-ink);
  --btn-fg: #fbf6ea;
  --btn-border: var(--paper-ink);
  box-shadow: 0 18px 34px -20px rgba(16, 26, 38, .65);
}
.fx-intro__paper .btn--primary:hover {
  --btn-bg: var(--paper-gold);
  --btn-fg: #fdf8ee;
  --btn-border: var(--paper-gold);
}
.fx-intro__paper .btn--quiet { color: var(--paper-ink-2); }
.fx-intro__paper .btn--quiet:hover { color: var(--paper-ink); background: rgba(118, 96, 62, .09); }
.fx-intro__arrow { transition: transform var(--dur-mic) var(--ease); }
.fx-intro__go:hover .fx-intro__arrow { transform: translateX(4px); }
.fx-intro__signed {
  margin-top: clamp(22px, 3vw, 30px);
  padding-top: clamp(14px, 2vw, 18px);
  border-top: 1px solid var(--paper-line);
  text-align: center;
  font-size: 10px;
  letter-spacing: .26em;
  color: var(--paper-ink-2);
  opacity: .9;
}

/* 移动端 */
@media (max-width: 640px) {
  .fx-intro { padding: 12vh var(--sp-4) 16vh; }
  .fx-intro__envelope { width: min(82vw, 322px); }
  .fx-intro__stamp { right: -3%; top: -7%; width: 19%; }
  .fx-intro__skip { top: 14px; right: 14px; min-height: 40px; padding: 0 14px; letter-spacing: .12em; }
  .fx-intro__hint { margin-top: 36px; letter-spacing: .26em; font-size: 12px; }
  .fx-intro__paper {
    width: 100%;
    max-height: min(70vh, 640px);
    padding: 26px 22px 22px;
    transform: none;
  }
  .fx-intro__paper::after { inset: 8px; }
  .fx-intro__title { letter-spacing: .2em; padding-left: .2em; }
  .fx-intro__quote { font-size: clamp(15.5px, 4.4vw, 18px); line-height: 1.95; }
  .fx-intro__sheet { padding-top: 4vh; }
  .fx-intro__foot { display: none; }
}

/* =========================================================
   7 · 降级
   ========================================================= */
/* 触屏 / 粗指针：自定义光标一律不出现 */
@media (hover: none), (pointer: coarse) {
  .fx-cursor { display: none !important; }
  html.has-custom-cursor,
  html.has-custom-cursor * { cursor: auto !important; }
}
/* 窄屏：开场信省掉重滤镜，保住低端机动效 */
@media (max-width: 640px) {
  .fx-intro__veil {
    -webkit-backdrop-filter: blur(10px);
    backdrop-filter: blur(10px);
  }
  #fx-grain { animation: none; }
}
/* 系统「减少动态」：所有循环动画只保留淡入 */
@media (prefers-reduced-motion: reduce) {
  #fx-grain { animation: none; }
  .fx-intro,
  .fx-intro__sky,
  .fx-intro__moon,
  .fx-intro__envelope,
  .fx-intro__paper,
  .fx-intro__hint,
  .fx-intro__stamp,
  .fx-intro__skip,
  .scroll-cue,
  .scroll-cue__line::after { animation: none !important; }
  .fx-intro__paper > * { opacity: 1; transform: none; transition: none; }
  .fx-intro.is-in { opacity: 1; visibility: visible; }
  .fx-cursor { display: none !important; }
  html.has-custom-cursor,
  html.has-custom-cursor * { cursor: auto !important; }
}
/* 站点设置里的「减少动态」（class 由 motion.js / ambient.js 挂上） */
:root.fx-reduced #fx-grain,
:root.fx-reduced .fx-intro,
:root.fx-reduced .fx-intro__sky,
:root.fx-reduced .fx-intro__moon,
:root.fx-reduced .fx-intro__envelope,
:root.fx-reduced .fx-intro__hint,
:root.fx-reduced .fx-intro__stamp,
:root.fx-reduced .fx-intro__skip,
:root.fx-reduced .fx-intro__paper,
:root.fx-reduced .scroll-cue,
:root.fx-reduced .scroll-cue__line::after,
:root.fx-reduced .split-char,
:root.fx-reduced [data-reveal] { animation: none !important; }
:root.fx-reduced .fx-intro__paper { opacity: 1 !important; }
:root.fx-reduced .fx-intro__paper > * {
  opacity: 1 !important;
  transform: none !important;
  transition: none !important;
}
:root.fx-reduced .fx-cursor { display: none !important; }
:root.fx-reduced [data-reveal],
:root.fx-reduced [data-reveal].is-in {
  opacity: 1 !important;
  transform: none !important;
  transition: none !important;
}
:root.fx-reduced .split-char {
  opacity: 1 !important;
  transform: none !important;
  transition: none !important;
}
:root.fx-reduced .fx-transition { transition: none !important; }