/* ==========================================================================
   ENTER THE FLOW — a living surface
   白纸、极细等高线、几乎不动的时间。克制是这里唯一的规则。
   ========================================================================== */

:root {
  --paper: #ffffff;

  /* 墨色只用一档，靠透明度分层 */
  --ink: #12181f;
  --ink-60: rgba(18, 24, 31, 0.6);
  --ink-42: rgba(18, 24, 31, 0.42);
  --ink-30: rgba(18, 24, 31, 0.3);
  --ink-16: rgba(18, 24, 31, 0.16);
  --hair: rgba(18, 24, 31, 0.12);

  --font-sans: "Inter", "Helvetica Neue", Helvetica, "Segoe UI", system-ui, -apple-system,
    sans-serif;
  --font-mono: ui-monospace, "SF Mono", "JetBrains Mono", "Cascadia Mono", Menlo, Consolas,
    monospace;

  --track-wide: 0.34em;
  --gutter: clamp(20px, 3.4vw, 46px);

  --ease: cubic-bezier(0.22, 0.61, 0.36, 1);
}

*,
*::before,
*::after {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
  scroll-snap-type: y proximity;
  background: var(--paper);
}

body {
  margin: 0;
  min-height: 100%;
  background: var(--paper);
  color: var(--ink);
  font-family: var(--font-sans);
  font-size: 15px;
  line-height: 1.6;
  overflow-x: hidden;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  text-rendering: optimizeLegibility;
}

::selection {
  background: rgba(18, 24, 31, 0.09);
}

:focus-visible {
  outline: 1px solid var(--ink-42);
  outline-offset: 5px;
}

/* --------------------------------------------------------------------------
   画布 + 表面层
   -------------------------------------------------------------------------- */

#flow {
  position: fixed;
  inset: 0;
  z-index: 0;
  display: block;
  width: 100%;
  height: 100%;
  pointer-events: none;
}

.surface {
  position: fixed;
  inset: 0;
  z-index: 1;
  pointer-events: none;
  overflow: hidden;
}

/* 极细颗粒，给纯白一点纸的质地 */
.surface__grain {
  position: absolute;
  inset: -50%;
  display: block;
  background-repeat: repeat;
  background-size: 128px 128px;
  opacity: 0.2;
  mix-blend-mode: multiply;
}

/* 区域色洗：克制到几乎只是白里的一点温度 */
.surface__wash {
  position: absolute;
  inset: 0;
  display: block;
  background:
    radial-gradient(58% 46% at 88% 8%, rgba(14, 165, 198, 0.05), transparent 68%),
    radial-gradient(52% 44% at 6% 92%, rgba(124, 92, 220, 0.045), transparent 70%),
    radial-gradient(40% 34% at 62% 58%, rgba(56, 130, 214, 0.03), transparent 72%);
}

/* 四边的极淡内收，避免画面「散掉」 */
.surface__edge {
  position: absolute;
  inset: 0;
  display: block;
  background: radial-gradient(
    130% 118% at 50% 46%,
    transparent 58%,
    rgba(18, 24, 31, 0.028) 100%
  );
}

/* --------------------------------------------------------------------------
   顶部
   -------------------------------------------------------------------------- */

.topbar {
  position: fixed;
  /* 必须高于 .menu（z-index 4）：否则 MENU 覆盖层一打开就把顶栏盖住，
     右上角的 CLOSE 按钮点都点不到，菜单只能靠 Esc 关。 */
  z-index: 5;
  top: 0;
  left: 0;
  right: 0;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 24px;
  padding: clamp(18px, 2.4vw, 30px) var(--gutter);
}

.mark {
  display: inline-flex;
  align-items: center;
  gap: 11px;
  color: var(--ink-60);
  text-decoration: none;
  transition: color 0.6s var(--ease);
}

.mark:hover {
  color: var(--ink);
}

.mark__glyph {
  display: block;
  color: var(--ink-42);
  transition: color 0.6s var(--ease);
}

.mark:hover .mark__glyph {
  color: var(--ink-60);
}

.mark__text,
.mark__num {
  font-family: var(--font-mono);
  font-size: 10.5px;
  letter-spacing: var(--track-wide);
  text-transform: uppercase;
  white-space: nowrap;
}

.mark__num {
  color: var(--ink-30);
}

.nav {
  display: flex;
  gap: clamp(18px, 2.6vw, 42px);
  

}

.nav__link {
  position: relative;
  font-family: var(--font-mono);
  font-size: 10.5px;
  letter-spacing: var(--track-wide);
  text-transform: uppercase;
  color: var(--ink-42);
  text-decoration: none;
  transition: color 0.6s var(--ease);
}

.nav__link::after {
  content: "";
  position: absolute;
  left: 0;
  bottom: -7px;
  width: 100%;
  height: 1px;
  background: currentColor;
  transform: scaleX(0);
  transform-origin: left;
  opacity: 0.4;
  transition: transform 0.75s var(--ease);
}

.nav__link:hover {
  color: var(--ink);
}

.nav__link:hover::after {
  transform: scaleX(1);
}

.menu-toggle {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  padding: 6px 0;
  border: 0;
  background: none;
  color: var(--ink-60);
  cursor: pointer;
  transition: color 0.6s var(--ease);
}

.menu-toggle:hover {
  color: var(--ink);
}

.menu-toggle__label {
  font-family: var(--font-mono);
  font-size: 10.5px;
  letter-spacing: var(--track-wide);
  text-transform: uppercase;
}

.menu-toggle__bars {
  display: grid;
  gap: 4px;
  width: 18px;
}

.menu-toggle__bars i {
  display: block;
  height: 1px;
  background: currentColor;
  transform-origin: left center;
  transition: transform 0.7s var(--ease), opacity 0.7s var(--ease);
}

body.is-menu-open .menu-toggle__bars i:first-child {
  transform: translateY(2.5px) rotate(13deg) scaleX(0.78);
}

body.is-menu-open .menu-toggle__bars i:last-child {
  transform: translateY(-2.5px) rotate(-13deg) scaleX(0.78);
}

/* --------------------------------------------------------------------------
   文档与章节
   -------------------------------------------------------------------------- */

.document {
  position: relative;
  z-index: 2;
}

.chapter {
  position: relative;
  height: 100vh;
  height: 100svh;
  scroll-snap-align: start;
}

/* 所有漂浮元素统一用 --x / --y 定位，天然不落在网格上 */
.label,
.lede,
.note,
.outro,
.signal,
.eyebrow {
  position: absolute;
  left: var(--x, 10%);
  top: var(--y, 50%);
}

/* 极细辅助文字：像悬浮在空间里，不像导航 */
.label {
  display: block;
  font-family: var(--font-mono);
  font-size: 10.5px;
  font-weight: 400;
  letter-spacing: var(--track-wide);
  text-transform: uppercase;
  color: var(--ink-42);
  white-space: nowrap;
  will-change: transform;
  transition: color 0.8s var(--ease);
}

.label.l-index {
  font-family: var(--font-sans);
  font-size: 12.5px;
  font-weight: 300;
  letter-spacing: 0.3em;
  color: var(--ink-30);
}

.eyebrow {
  color: var(--ink-60);
  font-size: 11px;
  letter-spacing: 0.44em;
}

.eyebrow::before {
  content: "";
  position: absolute;
  left: -3.2em;
  top: 50%;
  width: 2.4em;
  height: 1px;
  background: var(--ink-16);
}

/* --------------------------------------------------------------------------
   主标题
   -------------------------------------------------------------------------- */

.title {
  position: absolute;
  left: var(--gutter);
  top: 37%;
  margin: 0;
  font-size: clamp(26px, 3.2vw, 50px);
  font-weight: 300;
  line-height: 1.24;
  color: var(--ink);
  /* 补偿 letter-spacing 在行尾留下的空隙，让左对齐的视觉边界准确 */
  margin-right: -0.42em;
  user-select: none;
  white-space: nowrap;
}

.word {
  display: inline-block;
}

.word + .word {
  margin-left: 0.52em;
}

.ch {
  display: inline-block;
  letter-spacing: 0.42em;
  will-change: transform, opacity;
}

/* --------------------------------------------------------------------------
   正文型小段落
   -------------------------------------------------------------------------- */

.lede,
.note,
.outro {
  margin: 0;
  font-weight: 300;
  color: var(--ink-60);
  letter-spacing: 0.045em;
  will-change: transform;
}

.lede {
  max-width: 33ch;
  font-size: 13.5px;
  line-height: 2;
}

.note {
  max-width: 30ch;
  font-size: 13.5px;
  line-height: 2.05;
}

.outro {
  max-width: 26ch;
  font-size: 15px;
  line-height: 1.95;
}

/* --------------------------------------------------------------------------
   装饰与链接
   -------------------------------------------------------------------------- */

.hairline {
  position: absolute;
  left: var(--x);
  top: var(--y);
  width: var(--w, 12vw);
  height: 1px;
  background: linear-gradient(90deg, var(--ink-16), transparent);
  transform-origin: left center;
}

.signal {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  font-family: var(--font-mono);
  font-size: 10.5px;
  letter-spacing: var(--track-wide);
  text-transform: uppercase;
  color: var(--ink-42);
  text-decoration: none;
  white-space: nowrap;
  will-change: transform;
  transition: color 0.7s var(--ease);
}

.signal:hover {
  color: var(--ink);
}

.signal__dot {
  width: 5px;
  height: 5px;
  border-radius: 50%;
  background: currentColor;
  box-shadow: 0 0 0 0 currentColor;
  animation: breathe 5.5s var(--ease) infinite;
}

@keyframes breathe {
  0%,
  100% {
    box-shadow: 0 0 0 0 rgba(18, 24, 31, 0.16);
    opacity: 0.55;
  }
  50% {
    box-shadow: 0 0 0 6px rgba(18, 24, 31, 0);
    opacity: 1;
  }
}

/* 沿弧线排布的文字 */
.arclabel {
  position: absolute;
  left: 6%;
  top: 50%;
  width: 88%;
  height: auto;
  overflow: visible;
}

.arclabel__text {
  fill: var(--ink-30);
  font-family: var(--font-mono);
  font-size: 11.5px;
  letter-spacing: 0.42em;
  text-transform: uppercase;
}

/* --------------------------------------------------------------------------
   底部
   -------------------------------------------------------------------------- */

.footbar {
  position: fixed;
  z-index: 3;
  left: 0;
  right: 0;
  bottom: 0;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 20px;
  padding: clamp(16px, 2.2vw, 26px) var(--gutter);
  font-family: var(--font-mono);
  font-size: 10px;
  letter-spacing: var(--track-wide);
  text-transform: uppercase;
  color: var(--ink-30);
  pointer-events: none;
}

.footbar__scroll {
  display: inline-flex;
  align-items: center;
  gap: 10px;
}

.footbar__scroll-label {
  color: var(--ink-30);
}

.footbar__scroll-track {
  position: relative;
  display: block;
  width: 46px;
  height: 1px;
  background: var(--ink-16);
  overflow: hidden;
}

.footbar__scroll-track i {
  position: absolute;
  inset: 0;
  display: block;
  background: var(--ink-42);
  transform-origin: left center;
  animation: track 6.5s var(--ease) infinite;
}

@keyframes track {
  0% {
    transform: scaleX(0);
    opacity: 0;
  }
  22% {
    opacity: 1;
  }
  58% {
    transform: scaleX(1);
    opacity: 1;
  }
  100% {
    transform: scaleX(1);
    opacity: 0;
  }
}

.footbar__chapter b {
  font-weight: 400;
  color: var(--ink-60);
}

/* --------------------------------------------------------------------------
   MENU
   -------------------------------------------------------------------------- */

.menu {
  position: fixed;
  inset: 0;
  z-index: 4;
  display: grid;
  align-content: center;
  gap: clamp(30px, 5vw, 70px);
  padding: var(--gutter);
  background: rgba(255, 255, 255, 0.9);
  backdrop-filter: saturate(120%) blur(18px);
  -webkit-backdrop-filter: saturate(120%) blur(18px);
  opacity: 0;
  transition: opacity 0.85s var(--ease);
}

.menu[hidden] {
  display: none;
}

.menu.is-visible {
  opacity: 1;
}

.menu__inner {
  display: grid;
  gap: clamp(6px, 1.1vw, 14px);
  justify-items: start;
  margin-left: clamp(0px, 8vw, 140px);
}

.menu__item {
  display: inline-flex;
  align-items: baseline;
  gap: 22px;
  font-size: clamp(24px, 3.4vw, 46px);
  font-weight: 300;
  letter-spacing: 0.16em;
  color: var(--ink-60);
  text-decoration: none;
  opacity: 0;
  transform: translateY(14px);
  transition: color 0.7s var(--ease), opacity 0.9s var(--ease), transform 0.9s var(--ease);
  transition-delay: calc(var(--i, 0) * 70ms);
}

.menu.is-visible .menu__item {
  opacity: 1;
  transform: none;
}

.menu__item span {
  font-family: var(--font-mono);
  font-size: 10.5px;
  letter-spacing: var(--track-wide);
  color: var(--ink-30);
}

.menu__item:hover {
  color: var(--ink);
}

.menu__foot {
  margin: 0 0 0 clamp(0px, 8vw, 140px);
  font-family: var(--font-mono);
  font-size: 10px;
  letter-spacing: var(--track-wide);
  text-transform: uppercase;
  color: var(--ink-30);
}

/* --------------------------------------------------------------------------
   响应式：移动端保留构图与交互，但降低密度
   -------------------------------------------------------------------------- */

@media (max-width: 900px) {
  .nav {
    display: none;
  }

  .chapter {
    height: 100svh;
  }

  .title {
    top: 30%;
    font-size: clamp(23px, 6.6vw, 34px);
    white-space: normal;
    max-width: 12ch;
  }

  .lede {
    top: 50% !important;
    left: 6.5% !important;
    max-width: 26ch;
    font-size: 12.5px;
  }

  .l-explore {
    --x: 6% !important;
    --y: 68% !important;
  }

  .l-index {
    --x: 8% !important;
  }

  .l-year {
    --x: 72% !important;
    --y: 21% !important;
  }

  .l-territory {
    --x: 6% !important;
    --y: 80% !important;
  }

  .hairline {
    display: none;
  }

  .note {
    --x: 8% !important;
    --y: 22% !important;
    max-width: 24ch;
    font-size: 12.5px;
  }

  .l-still {
    --x: 8% !important;
    --y: 46% !important;
  }

  .l-slow {
    --x: 7% !important;
    --y: 84% !important;
  }

  .arclabel {
    left: 4%;
    top: 62%;
    width: 92%;
  }

  .arclabel__text {
    font-size: 9.5px;
    letter-spacing: 0.3em;
  }

  .outro {
    --x: 8% !important;
    --y: 34% !important;
    font-size: 13.5px;
  }

  .l-open {
    --x: 8% !important;
    --y: 62% !important;
    white-space: normal;
    max-width: 18ch;
  }

  .signal {
    --x: 8% !important;
    --y: 78% !important;
  }

  .footbar__meta {
    display: none;
  }

  .menu__inner,
  .menu__foot {
    margin-left: 0;
  }
}

@media (max-width: 560px) {
  .mark__num {
    display: none;
  }

  .title {
    letter-spacing: 0;
  }

  .footbar {
    justify-content: space-between;
  }
}

/* --------------------------------------------------------------------------
   尊重「减少动态效果」：CSS 动画全部停下，流场由 JS 出一帧静帧
   -------------------------------------------------------------------------- */

@media (prefers-reduced-motion: reduce) {
  html {
    scroll-behavior: auto;
    scroll-snap-type: none;
  }

  .signal__dot,
  .footbar__scroll-track i {
    animation: none;
  }

  .footbar__scroll-track i {
    transform: scaleX(1);
  }

  .menu,
  .menu__item,
  .label,
  .nav__link::after {
    transition-duration: 0.01ms;
  }
}