/* ============================================================
   PaperMaster 推广页 — 仿大疆 DJI 设计系统
   近单色电影感 · Helvetica Neue grotesque · 胶囊按钮 · 发丝玻璃
   ============================================================ */

/* ---------- 设计令牌 ---------- */
:root {
  /* 色彩：黑 / 白 / 石墨近单色，色彩由真实演示视频承载 */
  --ink: #000000;
  --carbon: #0b0b0d;
  --graphite: #16161a;
  --steel: #1f1f24;
  --mist: #86868b;
  --silver: #d2d2d7;
  --snow: #f5f5f7;
  --paper: #fbfbfd;
  --fg-dark: #1d1d1f;
  --fg-light: #f5f5f7;
  --accent: #ffffff;          /* 暗底动作色 = 纯白 */

  /* 真实产品点缀色（仅用于产品 UI mock 内，代表实际高亮/状态） */
  --hl-amber: #fbbf24;
  --hl-green: #34d399;
  --hl-blue: #60a5fa;
  --hl-pink: #f472b6;

  /* 字体：单一 grotesque 家族（大疆 / 瑞士风） */
  --font-sans: 'Helvetica Neue', Helvetica, Arial, 'PingFang SC', 'Hiragino Sans GB', 'Microsoft YaHei', sans-serif;
  --font-mono: 'SF Mono', ui-monospace, 'JetBrains Mono', Menlo, monospace;

  /* 节奏 */
  --container: 1200px;
  --gutter: clamp(20px, 5vw, 80px);
  --section-y: clamp(72px, 10vw, 140px);
  --radius-card: 20px;
  --radius-frame: 24px;
  --radius-pill: 999px;

  --nav-h: 64px;
  --ease: cubic-bezier(0.22, 1, 0.36, 1);
}

/* ---------- 重置 ---------- */
*,
*::before,
*::after { box-sizing: border-box; margin: 0; padding: 0; }

html {
  scroll-behavior: smooth;
  scroll-padding-top: var(--nav-h);
  -webkit-text-size-adjust: 100%;
}

body {
  font-family: var(--font-sans);
  font-size: 17px;
  line-height: 1.6;
  color: var(--fg-dark);
  background: var(--paper);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  overflow-x: hidden;
}

img, video, svg { display: block; max-width: 100%; }
a { color: inherit; text-decoration: none; }
button { font-family: inherit; cursor: pointer; border: 0; background: none; color: inherit; }
ul { list-style: none; }

::selection { background: var(--fg-dark); color: #fff; }

/* ---------- 排版阶梯 ---------- */
.eyebrow {
  font-size: 12.5px;
  font-weight: 500;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--mist);
}

h1, h2, h3 { font-weight: 600; line-height: 1.08; color: inherit; }

.display {
  font-size: clamp(44px, 7.5vw, 104px);
  font-weight: 600;
  letter-spacing: -0.035em;
  line-height: 1.02;
}

.h1 {
  font-size: clamp(40px, 6vw, 84px);
  font-weight: 600;
  letter-spacing: -0.03em;
  line-height: 1.04;
}

.h2 {
  font-size: clamp(34px, 4.6vw, 64px);
  font-weight: 600;
  letter-spacing: -0.025em;
  line-height: 1.06;
}

.h3 {
  font-size: clamp(22px, 2.4vw, 32px);
  font-weight: 600;
  letter-spacing: -0.015em;
  line-height: 1.2;
}

.lead {
  font-size: clamp(18px, 1.7vw, 23px);
  font-weight: 400;
  line-height: 1.55;
  letter-spacing: -0.005em;
  max-width: 46ch;
}

.muted { color: var(--mist); }

.mono {
  font-family: var(--font-mono);
  font-variant-numeric: tabular-nums;
}

/* ---------- 布局 ---------- */
.container {
  width: 100%;
  max-width: var(--container);
  margin: 0 auto;
  padding-inline: var(--gutter);
}

.section { padding-block: var(--section-y); position: relative; }
.section--dark { background: var(--carbon); color: var(--fg-light); }
.section--ink { background: var(--ink); color: var(--fg-light); }
.section--light { background: var(--paper); color: var(--fg-dark); }
.section--snow { background: var(--snow); color: var(--fg-dark); }

.section--dark .muted,
.section--ink .muted { color: var(--mist); }

.section-head { max-width: 760px; margin-bottom: clamp(40px, 5vw, 72px); }
.section-head .lead { margin-top: 22px; }

/* ---------- 按钮 ---------- */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 10px;
  padding: 15px 30px;
  border-radius: var(--radius-pill);
  font-size: 15.5px;
  font-weight: 500;
  letter-spacing: 0.01em;
  line-height: 1;
  transition: transform 0.35s var(--ease), background 0.3s, color 0.3s, border-color 0.3s, opacity 0.3s;
  white-space: nowrap;
}
.btn svg { width: 18px; height: 18px; }

/* 暗底：主按钮 = 白底黑字 */
.on-dark .btn--primary { background: var(--accent); color: #000; }
.on-dark .btn--primary:hover { transform: translateY(-2px); }
.on-dark .btn--ghost { background: rgba(255,255,255,0.04); color: var(--fg-light); border: 1px solid rgba(255,255,255,0.22); }
.on-dark .btn--ghost:hover { border-color: rgba(255,255,255,0.6); transform: translateY(-2px); }

/* 亮底：主按钮 = 黑底白字 */
.on-light .btn--primary { background: var(--fg-dark); color: #fff; }
.on-light .btn--primary:hover { transform: translateY(-2px); }
.on-light .btn--ghost { background: transparent; color: var(--fg-dark); border: 1px solid var(--silver); }
.on-light .btn--ghost:hover { border-color: var(--fg-dark); transform: translateY(-2px); }

/* ---------- 导航 ---------- */
.nav {
  position: fixed;
  top: 0; left: 0; right: 0;
  z-index: 100;
  height: var(--nav-h);
  display: flex;
  align-items: center;
  transition: background 0.4s var(--ease), border-color 0.4s, backdrop-filter 0.4s;
  border-bottom: 1px solid transparent;
}
.nav.is-scrolled {
  background: rgba(10, 10, 13, 0.72);
  backdrop-filter: saturate(180%) blur(20px);
  -webkit-backdrop-filter: saturate(180%) blur(20px);
  border-bottom-color: rgba(255,255,255,0.08);
}
.nav__inner {
  width: 100%;
  max-width: var(--container);
  margin: 0 auto;
  padding-inline: var(--gutter);
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 24px;
}
.brand { display: inline-flex; align-items: center; gap: 10px; color: #fff; font-weight: 600; letter-spacing: -0.01em; font-size: 18px; }
.brand__mark { width: 26px; height: 26px; flex: none; }
.nav__links { display: flex; align-items: center; gap: 34px; }
.nav__links a { color: rgba(245,245,247,0.82); font-size: 14.5px; font-weight: 400; transition: color 0.25s; }
.nav__links a:hover { color: #fff; }
.nav__cta { display: inline-flex; align-items: center; gap: 14px; }
.nav__download {
  padding: 10px 22px;
  border-radius: var(--radius-pill);
  background: #fff; color: #000;
  font-size: 14px; font-weight: 500; letter-spacing: 0.01em;
  transition: transform 0.3s var(--ease), opacity 0.3s;
}
.nav__download:hover { transform: translateY(-2px); }
.nav__burger { display: none; width: 28px; height: 28px; color: #fff; }
/* 移动端菜单：桌面默认隐藏，仅在 760px 以下且 .is-open 时展开 */
.nav__menu { display: none; }

/* ---------- 英雄区 ---------- */
.hero {
  position: relative;
  background: var(--ink);
  color: var(--fg-light);
  min-height: 100svh;
  display: flex;
  align-items: flex-end;
  overflow: hidden;
  isolation: isolate;
}
.hero__video {
  position: absolute;
  inset: 0;
  width: 100%; height: 100%;
  object-fit: cover;
  z-index: -2;
}
/* 电影感渐隐 + 聚光 vignette（非装饰性靛紫，纯黑压暗） */
.hero::after {
  content: "";
  position: absolute;
  inset: 0;
  z-index: -1;
  background:
    linear-gradient(180deg, rgba(0,0,0,0.55) 0%, rgba(0,0,0,0.15) 32%, rgba(0,0,0,0.45) 62%, rgba(0,0,0,0.92) 100%),
    radial-gradient(120% 90% at 50% 8%, rgba(0,0,0,0) 40%, rgba(0,0,0,0.5) 100%);
}
.hero__inner {
  width: 100%;
  max-width: var(--container);
  margin: 0 auto;
  padding: 0 var(--gutter) clamp(96px, 14vh, 170px);
}
.hero__eyebrow { color: rgba(255,255,255,0.7); margin-bottom: 26px; }
.hero__title { max-width: 16ch; }
.hero__title .accent-line { display: block; }
.hero__sub {
  margin-top: 30px;
  color: rgba(245,245,247,0.82);
  max-width: 44ch;
}
.hero__actions { margin-top: 42px; display: flex; flex-wrap: wrap; gap: 16px; }
.hero__meta {
  margin-top: 38px;
  display: flex; flex-wrap: wrap; gap: 14px 28px;
  color: rgba(245,245,247,0.6);
  font-size: 13.5px;
  letter-spacing: 0.02em;
}
.hero__meta span { display: inline-flex; align-items: center; gap: 8px; }
.hero__meta .dot { width: 5px; height: 5px; border-radius: 50%; background: rgba(255,255,255,0.4); }

/* 滚动提示 */
.scroll-hint {
  position: absolute;
  bottom: 26px; left: 50%;
  transform: translateX(-50%);
  color: rgba(255,255,255,0.45);
  font-size: 11px; letter-spacing: 0.22em; text-transform: uppercase;
  display: flex; flex-direction: column; align-items: center; gap: 10px;
  z-index: 1;
}
.scroll-hint .bar { width: 1px; height: 34px; background: linear-gradient(rgba(255,255,255,0.6), transparent); animation: hint 2.4s var(--ease) infinite; }
@keyframes hint { 0%,100% { opacity: 0.3; transform: scaleY(0.6); } 50% { opacity: 1; transform: scaleY(1); } }

/* ---------- 视频展示区 ---------- */
.showcase { background: var(--carbon); color: var(--fg-light); }
.showcase__frame {
  position: relative;
  border-radius: var(--radius-frame);
  overflow: hidden;
  border: 1px solid rgba(255,255,255,0.1);
  background: #000;
  aspect-ratio: 16 / 9;
  box-shadow: 0 40px 120px rgba(0,0,0,0.6);
}
.showcase__frame video { width: 100%; height: 100%; object-fit: cover; }

/* ---------- 分屏功能区 ---------- */
.split {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: clamp(40px, 6vw, 96px);
  align-items: center;
}
.split--reverse .split__media { order: 2; }
.split__body .eyebrow { margin-bottom: 22px; }
.split__body .h2 { max-width: 15ch; }
.split__body p { margin-top: 24px; color: var(--mist); max-width: 46ch; }
.split__list { margin-top: 30px; display: grid; gap: 16px; }
.split__list li {
  display: flex; gap: 14px; align-items: flex-start;
  font-size: 15.5px; line-height: 1.5;
}
.split__list .tick {
  flex: none; width: 22px; height: 22px; margin-top: 1px;
  border-radius: 50%;
  display: grid; place-items: center;
}
.on-dark .tick { background: rgba(255,255,255,0.1); color: #fff; }
.on-light .tick { background: rgba(0,0,0,0.06); color: var(--fg-dark); }
.tick svg { width: 12px; height: 12px; }

.section + .split,
.section .split { margin-top: clamp(40px, 6vw, 80px); }

/* ---------- 产品 UI mock（PaperMaster 阅读器） ---------- */
.mock {
  position: relative;
  border-radius: var(--radius-frame);
  background: var(--graphite);
  border: 1px solid rgba(255,255,255,0.08);
  overflow: hidden;
  box-shadow: 0 50px 130px rgba(0,0,0,0.55);
  font-size: 13px;
  color: var(--fg-light);
}
.mock__bar {
  display: flex; align-items: center; gap: 10px;
  padding: 12px 16px;
  background: #111114;
  border-bottom: 1px solid rgba(255,255,255,0.07);
}
.mock__dots { display: flex; gap: 7px; }
.mock__dots i { width: 11px; height: 11px; border-radius: 50%; background: #2a2a2e; display: block; }
.mock__url {
  flex: 1; margin-left: 8px;
  background: rgba(255,255,255,0.05);
  border-radius: 8px;
  padding: 6px 12px;
  font-family: var(--font-mono);
  font-size: 11.5px;
  color: var(--mist);
  display: flex; align-items: center; gap: 8px;
}
.mock__url b { color: rgba(255,255,255,0.85); font-weight: 500; }
.mock__body { display: grid; grid-template-columns: 1.55fr 1fr; min-height: 360px; }
.mock__page {
  background: #efefef;
  color: #333;
  padding: 26px 30px;
  position: relative;
}
.mock__page h4 { font-size: 15px; color: #1a1a1a; margin-bottom: 10px; font-weight: 700; }
.mock__page .auth { font-size: 11px; color: #888; margin-bottom: 18px; }
.mock__line { height: 8px; background: #d8d8d8; border-radius: 3px; margin-bottom: 9px; }
.mock__line.w70 { width: 70%; } .mock__line.w85 { width: 85%; } .mock__line.w50 { width: 50%; } .mock__line.w92 { width: 92%; }
.mock__hl { background: linear-gradient(transparent 55%, rgba(251,191,36,0.55) 55%); }
.mock__hl--g { background: linear-gradient(transparent 55%, rgba(52,211,153,0.5) 55%); }
.mock__side {
  background: #131316;
  border-left: 1px solid rgba(255,255,255,0.07);
  display: flex; flex-direction: column;
}
.mock__tabs { display: flex; gap: 4px; padding: 10px 10px 0; border-bottom: 1px solid rgba(255,255,255,0.06); }
.mock__tab {
  font-size: 10.5px; color: var(--mist); padding: 8px 9px; letter-spacing: 0.02em;
  border-bottom: 2px solid transparent;
}
.mock__tab.is-active { color: #fff; border-bottom-color: #fff; }
.mock__panel { padding: 16px; overflow: hidden; }
.mock__bubble {
  background: rgba(255,255,255,0.06);
  border-radius: 12px 12px 12px 3px;
  padding: 11px 13px;
  font-size: 12px; line-height: 1.55; color: rgba(245,245,247,0.88);
  margin-bottom: 10px;
}
.mock__bubble--ai { border-radius: 12px 12px 3px 12px; background: rgba(255,255,255,0.1); }
.mock__formula {
  font-family: var(--font-mono); font-size: 13px; color: #fff;
  background: rgba(255,255,255,0.05); border: 1px dashed rgba(255,255,255,0.18);
  border-radius: 8px; padding: 10px 12px; margin: 10px 0;
}
.mock__chip {
  display: inline-flex; align-items: center; gap: 5px;
  font-size: 10.5px; padding: 3px 9px; border-radius: 999px;
  background: rgba(255,255,255,0.08); color: rgba(255,255,255,0.8);
  margin-right: 6px; margin-top: 6px;
}
.mock__chip .d { width: 6px; height: 6px; border-radius: 50%; }
.mock__tag { font-size: 10px; letter-spacing: 0.12em; text-transform: uppercase; color: var(--mist); margin-bottom: 8px; }

/* 框选识别 mock 变体 */
.mock--region .mock__page::after {
  content: ""; position: absolute; inset: auto 22px 60px 22px; height: 64px;
  border: 1.5px dashed var(--hl-blue); border-radius: 6px;
  background: rgba(96,165,250,0.08);
}

/* ---------- 能力带（真实事实，非编造指标） ---------- */
.cap {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 1px;
  background: rgba(255,255,255,0.08);
  border: 1px solid rgba(255,255,255,0.08);
  border-radius: var(--radius-card);
  overflow: hidden;
}
.section--light .cap { background: var(--silver); border-color: var(--silver); }
.cap__cell {
  background: var(--carbon);
  padding: clamp(28px, 3.5vw, 44px) clamp(20px, 2.4vw, 32px);
}
.section--light .cap__cell { background: var(--paper); }
.cap__num {
  font-size: clamp(40px, 5vw, 64px);
  font-weight: 600;
  letter-spacing: -0.04em;
  line-height: 1;
}
.cap__label { margin-top: 12px; color: var(--mist); font-size: 14px; line-height: 1.45; }

/* ---------- 三步使用 ---------- */
.steps { display: grid; grid-template-columns: repeat(auto-fit, minmax(min(100%, 260px), 1fr)); gap: clamp(24px, 4vw, 48px); }
.step { position: relative; padding-top: 8px; min-width: 0; }
.step__num {
  font-family: var(--font-mono);
  font-size: 13px; letter-spacing: 0.1em; color: var(--mist);
  margin-bottom: 22px;
}
.step__icon {
  width: 52px; height: 52px; border-radius: 14px;
  display: grid; place-items: center; margin-bottom: 24px;
}
.on-dark .step__icon { background: rgba(255,255,255,0.06); color: #fff; border: 1px solid rgba(255,255,255,0.1); }
.on-light .step__icon { background: rgba(0,0,0,0.04); color: var(--fg-dark); border: 1px solid var(--silver); }
.step__icon svg { width: 24px; height: 24px; }
.step h3 { margin-bottom: 14px; }
.step p { color: var(--mist); font-size: 15.5px; line-height: 1.55; }
.step .mono-code {
  display: inline-block; margin-top: 16px;
  font-family: var(--font-mono); font-size: 12.5px;
  padding: 8px 12px; border-radius: 8px;
  max-width: 100%; overflow-wrap: anywhere; word-break: break-word;
}
.on-dark .step .mono-code { background: rgba(255,255,255,0.06); color: rgba(255,255,255,0.85); }
.on-light .step .mono-code { background: var(--snow); color: var(--fg-dark); border: 1px solid var(--silver); }

/* ---------- 下载 CTA ---------- */
.cta {
  position: relative;
  background: var(--ink);
  color: var(--fg-light);
  text-align: center;
  overflow: hidden;
}
.cta::before {
  content: ""; position: absolute; inset: 0;
  background: radial-gradient(80% 60% at 50% 0%, rgba(255,255,255,0.07), transparent 60%);
}
.cta__inner { position: relative; max-width: 760px; margin: 0 auto; }
.cta .h1 { max-width: 14ch; margin: 0 auto; }
.cta p { margin: 26px auto 0; color: rgba(245,245,247,0.7); max-width: 48ch; }
.cta__actions { margin-top: 42px; display: flex; flex-wrap: wrap; gap: 16px; justify-content: center; }
.cta__note { margin-top: 24px; color: var(--mist); font-size: 13.5px; }
.cta__note .mono { color: rgba(255,255,255,0.8); }

/* 大下载卡 */
.dl-card {
  margin-top: 56px;
  display: grid;
  grid-template-columns: 1fr auto;
  gap: 32px;
  align-items: center;
  text-align: left;
  background: rgba(255,255,255,0.04);
  border: 1px solid rgba(255,255,255,0.1);
  border-radius: var(--radius-card);
  padding: clamp(24px, 3vw, 40px);
}
.dl-card__title { font-size: 22px; font-weight: 600; letter-spacing: -0.015em; }
.dl-card__meta { margin-top: 8px; color: var(--mist); font-size: 14px; display: flex; flex-wrap: wrap; gap: 8px 18px; }
.dl-card__meta .mono { color: rgba(255,255,255,0.78); }

/* ---------- 页脚 ---------- */
.footer { background: var(--carbon); color: rgba(245,245,247,0.7); padding-block: clamp(56px, 7vw, 88px) 40px; }
.footer__top {
  display: grid;
  grid-template-columns: 1.6fr 1fr 1fr 1fr;
  gap: 40px;
  padding-bottom: 48px;
  border-bottom: 1px solid rgba(255,255,255,0.08);
}
.footer__brand .brand { margin-bottom: 18px; }
.footer__brand p { font-size: 14px; line-height: 1.6; max-width: 34ch; }
.footer__col h5 { font-size: 12.5px; letter-spacing: 0.12em; text-transform: uppercase; color: #fff; margin-bottom: 18px; font-weight: 500; }
.footer__col li { margin-bottom: 11px; }
.footer__col a { font-size: 14px; transition: color 0.25s; }
.footer__col a:hover { color: #fff; }
.footer__bottom {
  display: flex; flex-wrap: wrap; gap: 16px; justify-content: space-between; align-items: center;
  padding-top: 28px; font-size: 13px; color: var(--mist);
}

/* ---------- 滚动揭示 ---------- */
.reveal { opacity: 0; transform: translateY(28px); transition: opacity 0.9s var(--ease), transform 0.9s var(--ease); will-change: opacity, transform; }
.reveal.is-in { opacity: 1; transform: none; }
.reveal[data-delay="1"] { transition-delay: 0.08s; }
.reveal[data-delay="2"] { transition-delay: 0.16s; }
.reveal[data-delay="3"] { transition-delay: 0.24s; }

@media (prefers-reduced-motion: reduce) {
  * { animation: none !important; transition: none !important; }
  .reveal { opacity: 1; transform: none; }
  html { scroll-behavior: auto; }
}

/* ---------- 响应式 ---------- */
@media (max-width: 980px) {
  .split { grid-template-columns: 1fr; gap: 44px; }
  .split--reverse .split__media { order: 0; }
  .cap { grid-template-columns: repeat(2, 1fr); }
  .footer__top { grid-template-columns: 1fr 1fr; gap: 32px; }
}

@media (max-width: 760px) {
  .nav__links { display: none; }
  .nav__burger { display: block; }
  /* 三步上手：移动端折叠为单列，避免长 mono 文本撑破视口 */
  .steps { grid-template-columns: 1fr; gap: 36px; }
  .nav__cta .nav__download { padding: 9px 16px; font-size: 13px; }

  /* 移动端展开菜单 */
  .nav__menu {
    position: fixed; inset: var(--nav-h) 0 auto 0;
    background: rgba(8,8,10,0.96);
    backdrop-filter: blur(20px); -webkit-backdrop-filter: blur(20px);
    padding: 20px var(--gutter) 32px;
    display: none; flex-direction: column; gap: 6px;
    border-bottom: 1px solid rgba(255,255,255,0.08);
  }
  .nav.is-open .nav__menu { display: flex; }
  .nav__menu a { padding: 14px 0; font-size: 20px; color: #fff; border-bottom: 1px solid rgba(255,255,255,0.06); }

  .mock__body { grid-template-columns: 1.3fr 1fr; min-height: 300px; }
  .dl-card { grid-template-columns: 1fr; text-align: left; }
}

@media (max-width: 560px) {
  body { font-size: 16px; }
  .hero__meta { gap: 10px 18px; }
  .cap { grid-template-columns: 1fr; }
  .footer__top { grid-template-columns: 1fr; gap: 28px; }
  .footer__bottom { flex-direction: column; align-items: flex-start; }
  .mock__body { grid-template-columns: 1fr; }
  .mock__side { border-left: 0; border-top: 1px solid rgba(255,255,255,0.07); }
  .btn { width: 100%; }
  .hero__actions, .cta__actions { flex-direction: column; }
  .hero__actions .btn, .cta__actions .btn { width: 100%; }
}