:root {
  color-scheme: light;

  --bg: #ffffff;
  --bg-soft: #f8f9fa;
  --bg-elev: #ffffff;
  --bg-tint: #edf6ff;
  --bg-tint-2: #f2f6ff;

  --ink: #1f2126;
  --ink-2: #444546;
  --muted: #6b7280;
  --faint: #9a9eab;
  --line: #e5e7eb;
  --line-strong: #d1d5db;

  --blue: #0175ff;
  --blue-strong: #005cd6;
  --blue-soft: #e6f2ff;
  --sky: #4a9eff;
  --sky-deep: #216ed8;
  --sky-pale: #edf6ff;

  --r-sm: 6px;
  --r: 8px;
  --r-md: 12px;
  --r-lg: 16px;
  --r-xl: 24px;
  --r-pill: 999px;

  --sh-1: 0 1px 3px rgba(0, 0, 0, .04), 0 1px 2px rgba(0, 0, 0, .06);
  --sh-2: 0 4px 12px rgba(0, 0, 0, .06), 0 2px 4px rgba(0, 0, 0, .04);
  --sh-3: 0 12px 32px rgba(0, 0, 0, .08), 0 4px 8px rgba(0, 0, 0, .04);
  --sh-blue: 0 4px 16px rgba(1, 117, 255, .24);

  --font-serif: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'PingFang SC', 'Hiragino Sans GB', 'Microsoft YaHei', sans-serif;
  --font-sans: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'PingFang SC', 'Hiragino Sans GB', 'Microsoft YaHei', 'Helvetica Neue', sans-serif;
  --font-mono: ui-monospace, SFMono-Regular, 'SF Mono', Menlo, Consolas, 'Liberation Mono', monospace;

  --container: 1840px;
  --gutter: clamp(20px, 2.8vw, 56px);
  --section-y: clamp(100px, 11vw, 140px);
  --section-y-sm: clamp(64px, 8vw, 96px);

  --cta-blue: var(--blue);
  --cta-blue-deep: #005cd6;

  --ease: cubic-bezier(.22, 1, .36, 1);
  --dur-1: .2s;
  --dur-2: .38s;
  --dur-3: .6s;
  --dur-4: 1s;
}

*, *::before, *::after { box-sizing: border-box; }
* { margin: 0; }
html { -webkit-text-size-adjust: 100%; scroll-behavior: smooth; }
body {
  font-family: var(--font-sans);
  font-size: 16px;
  line-height: 1.7;
  color: var(--ink-2);
  background: var(--bg);
  -webkit-font-smoothing: antialiased;
  overflow-x: hidden;
  /* 深色页脚需贴底：内容短的页面（download.php）否则页脚下方会露出白底 */
  display: flex; flex-direction: column; min-height: 100svh;
}
body > main { flex: 1 0 auto; }
img, svg, video { display: block; max-width: 100%; }
button, input, select, textarea { font: inherit; color: inherit; }
button { background: none; border: 0; padding: 0; cursor: pointer; }
a { color: inherit; text-decoration: none; }
ul, ol { padding: 0; list-style: none; }
/* 兜底：作者样式的 display 不得覆盖 hidden 属性（.plans-layout 曾因此全部显示） */
[hidden] { display: none !important; }

h1, h2, h3, h4 {
  font-family: var(--font-serif);
  font-weight: 600;
  color: var(--ink);
  line-height: 1.16;
  letter-spacing: -.01em;
}
::selection { background: var(--blue); color: #fff; }
:focus-visible { outline: 2px solid var(--blue); outline-offset: 3px; border-radius: 4px; }
::-webkit-scrollbar { width: 10px; }
::-webkit-scrollbar-thumb { background: var(--line-strong); border-radius: 99px; border: 3px solid var(--bg); }

.wrap { width: min(var(--container), 100% - (var(--gutter) * 2)); margin-inline: auto; }
.wrap-narrow { width: min(680px, 100% - (var(--gutter) * 2)); margin-inline: auto; }
.section { padding-block: var(--section-y); position: relative; }
.section--soft { background: var(--bg-soft); }
.section--tint { background: linear-gradient(180deg, #f5f9ff 0%, #eef4fc 100%); }
.section--flush { padding-top: 0; }
.section--tight { padding-block: var(--section-y-sm); }

.eyebrow {
  display: inline-flex; align-items: center; gap: 8px;
  font-family: var(--font-sans);
  font-size: 12px; font-weight: 600;
  letter-spacing: .18em; text-transform: uppercase;
  color: var(--blue);
}
.display { font-size: clamp(40px, 6.4vw, 76px); line-height: 1.1; }
.h1 { font-size: clamp(34px, 5vw, 58px); line-height: 1.14; }
.h2 { font-size: clamp(28px, 3.6vw, 42px); line-height: 1.2; }
.h3 { font-size: clamp(19px, 2vw, 22px); line-height: 1.35; }
.lead { font-size: clamp(16px, 1.5vw, 18px); line-height: 1.75; color: var(--muted); max-width: 56ch; }
.muted { color: var(--muted); }
.faint { color: var(--faint); }
.small { font-size: 14px; }
.micro { font-size: 13px; line-height: 1.6; color: var(--muted); }
.mono { font-family: var(--font-mono); font-variant-numeric: tabular-nums; }
.grad-text { color: var(--ink); }
.hairline { height: 1px; background: var(--line); border: 0; }

.tlink { position: relative; color: var(--blue); font-weight: 500; }
.tlink::after {
  content: ''; position: absolute; left: 0; right: 0; bottom: -2px; height: 1px;
  background: currentColor; transform: scaleX(0); transform-origin: right;
  transition: transform var(--dur-2) var(--ease);
}
.tlink:hover::after { transform: scaleX(1); transform-origin: left; }

.btn {
  --btn-h: 46px;
  position: relative; display: inline-flex; align-items: center; justify-content: center; gap: 8px;
  min-height: var(--btn-h); padding: 0 24px;
  border-radius: var(--r); font-size: 15px; font-weight: 500; white-space: nowrap;
  transition: transform var(--dur-1) var(--ease), background-color var(--dur-1) var(--ease),
              border-color var(--dur-1) var(--ease), box-shadow var(--dur-2) var(--ease),
              color var(--dur-1) var(--ease);
}
.btn .i { width: 16px; height: 16px; flex: none; transition: transform var(--dur-2) var(--ease); }
.btn:active { transform: translateY(1px); }
.btn--primary, .btn--brand { background: var(--blue); color: #fff;}
.btn--primary:hover, .btn--brand:hover { background: var(--blue-strong); transform: translateY(-1px); }
.btn--primary:hover .i-arrow, .btn--brand:hover .i-arrow { transform: translateX(3px); }
.btn--ghost { background: var(--bg-elev); color: var(--ink); border: 1px solid var(--line-strong); }
.btn--ghost:hover { border-color: var(--ink); transform: translateY(-1px); box-shadow: var(--sh-1); }
.btn--soft { background: var(--bg-soft); color: var(--ink); }
.btn--soft:hover { background: var(--line); }
.btn--lg { --btn-h: 52px; padding: 0 30px; font-size: 16px; border-radius: var(--r-md); }
.btn--sm { --btn-h: 38px; padding: 0 18px; font-size: 14px; border-radius: var(--r-sm); }
.btn--block { width: 100%; }
.btn--pill { border-radius: var(--r-pill); }
.btn-icon { display: inline-flex; align-items: center; justify-content: center; width: 38px; height: 38px; border-radius: var(--r); color: var(--muted); transition: background-color var(--dur-1), color var(--dur-1); }
.btn-icon:hover { background: var(--bg-soft); color: var(--ink); }

.site-header {
  position: sticky; top: 0; z-index: 60;
  background: color-mix(in srgb, var(--bg) 86%, transparent);
  -webkit-backdrop-filter: blur(12px); backdrop-filter: blur(12px);
  border-bottom: 1px solid transparent;
  transition: border-color var(--dur-2) var(--ease);
}
.site-header.is-stuck { border-bottom-color: var(--line); }
.nav { display: flex; align-items: center; gap: 28px; height: 70px; }
.brand { display: inline-flex; align-items: center; gap: 10px; font-family: var(--font-sans); font-weight: 700; font-size: 21px; letter-spacing: -.01em; color: var(--blue); }
.brand .logo-mark { width: 28px; height: 28px; }
.brand .logo-full { height: 30px; width: auto; display: block; }
.site-header .brand { font-size: 20px; color: var(--ink); transition: color var(--dur-2) var(--ease); }
.nav-links { display: flex; align-items: center; gap: 4px; margin-inline: auto; }
.nav-link { position: relative; padding: 8px 14px; font-size: 15px; font-weight: 500; color: var(--ink-2); border-radius: var(--r-sm); transition: color var(--dur-1); }
.nav-link:hover { color: var(--blue); }
.nav-link.is-active { color: var(--ink); font-weight: 600; }
.nav-cta { display: flex; align-items: center; gap: 12px; }
.nav-signin { padding: 8px 10px; font-size: 15px; font-weight: 500; color: var(--ink-2); transition: color var(--dur-1); }
.nav-signin:hover { color: var(--blue); }
.nav-burger { display: none; }
.nav-burger span { display: block; width: 18px; height: 1.5px; background: var(--ink); border-radius: 2px; transition: transform var(--dur-2) var(--ease), opacity var(--dur-2); }
.nav-burger span + span { margin-top: 5px; }
.nav-burger[aria-expanded="true"] span:nth-child(1) { transform: translateY(6.5px) rotate(45deg); }
.nav-burger[aria-expanded="true"] span:nth-child(2) { opacity: 0; }
.nav-burger[aria-expanded="true"] span:nth-child(3) { transform: translateY(-6.5px) rotate(-45deg); }
.nav-drawer { position: fixed; inset: 68px 0 auto 0; z-index: 55; background: var(--bg); border-bottom: 1px solid var(--line); padding: 12px var(--gutter) 28px; display: none; flex-direction: column; gap: 2px; box-shadow: var(--sh-2); }
.nav-drawer.is-open { display: flex; animation: drawer-in var(--dur-3) var(--ease); }
.nav-drawer .nav-link { font-size: 17px; padding: 14px 4px; border-bottom: 1px solid var(--line); border-radius: 0; }
.nav-drawer .btn { margin-top: 18px; }
@keyframes drawer-in { from { opacity: 0; transform: translateY(-8px); } to { opacity: 1; transform: none; } }

/* fixed 不占位：只用于首屏自带深色底的页面（index.php 视频 hero）；未滚动时白字透明，滚动后（is-stuck）回到默认白色导航 */
.site-header--overlay {
  position: fixed; inset: 0 0 auto 0;
  transition: background-color var(--dur-2) var(--ease), border-color var(--dur-2) var(--ease);
}
.site-header--overlay:not(.is-stuck) {
  background: transparent;
  -webkit-backdrop-filter: none; backdrop-filter: none;
  border-bottom-color: rgba(255, 255, 255, .1);
}
.site-header--overlay:not(.is-stuck) .brand { color: #fff; }
.site-header--overlay:not(.is-stuck) .nav-link, .site-header--overlay:not(.is-stuck) .nav-signin { color: rgba(255, 255, 255, .72); }
.site-header--overlay:not(.is-stuck) .nav-link:hover, .site-header--overlay:not(.is-stuck) .nav-link.is-active, .site-header--overlay:not(.is-stuck) .nav-signin:hover { color: #fff; }
.site-header--overlay:not(.is-stuck) .nav-burger span { background: #fff; }
.site-header--overlay:not(.is-stuck) .btn-icon:hover { background: rgba(255, 255, 255, .1); }

.scroll-progress { display: none; }

.site-footer { display: flex; flex-direction: column; min-height: 100svh; background: #0e1011; color: rgba(255, 255, 255, .58); padding-block: clamp(48px, 5vw, 88px) clamp(24px, 3vw, 40px); }
.site-footer > .wrap { flex: 1; display: flex; flex-direction: column; }
/* margin-bottom:auto 吃掉占满一屏后的剩余高度，大字与底部行始终贴屏底 */
.footer-grid { display: grid; grid-template-columns: repeat(8, minmax(0, 1fr)) minmax(190px, 1.5fr); gap: 40px clamp(20px, 2.2vw, 40px); margin-bottom: auto; }
.footer-col h4 { font-family: var(--font-sans); font-size: 15px; font-weight: 600; color: #fff; margin-bottom: 16px; }
.footer-col a { display: block; padding: 5px 0; font-size: 15px; line-height: 1.6; color: rgba(255, 255, 255, .58); transition: color var(--dur-1); }
.footer-col a:hover { color: #fff; }
.footer-col .footer-ask { display: flex; align-items: center; gap: 10px; margin-bottom: 10px; padding: 9px 14px; border: 1px solid rgba(255, 255, 255, .18); border-radius: var(--r); font-size: 14px; color: rgba(255, 255, 255, .72); transition: color var(--dur-1), border-color var(--dur-1), background-color var(--dur-1); }
.footer-col .footer-ask:hover { color: #fff; border-color: rgba(255, 255, 255, .42); background: rgba(255, 255, 255, .04); }
.footer-ask .i { flex: none; width: 16px; height: 16px; }
.footer-cta { padding-bottom: clamp(32px, 3vw, 48px); margin-bottom: clamp(40px, 4vw, 64px); display: flex; flex-wrap: wrap; align-items: flex-end; justify-content: space-between; gap: 28px 48px; border-bottom: 1px solid rgba(255, 255, 255, .1); }
.footer-cta-title { font-size: clamp(28px, 3.4vw, 60px); line-height: 1.12; font-weight: 600; letter-spacing: -.02em; color: #fff; }
.footer-cta-title span { display: block; color: rgba(255, 255, 255, .42); }
.footer-cta-side { display: flex; flex-direction: column; align-items: flex-end; gap: 16px; }
.footer-cta-actions { display: flex; flex-wrap: wrap; gap: 12px; }
.footer-cta-note { font-size: 13px; color: rgba(255, 255, 255, .5); }
.footer-cta-note a { color: rgba(255, 255, 255, .82); text-decoration: underline; text-underline-offset: 3px; transition: color var(--dur-1); }
.footer-cta-note a:hover { color: #fff; }
/* 页脚大字自托管：不依赖 Google Fonts 可达性，字形与 fitWordmark 的宽度测量始终一致 */
@font-face { font-family: 'FL Wordmark'; src: url('../fonts/geist-latin.woff2') format('woff2'); font-weight: 600; font-display: swap; }
.footer-wordmark { display: block; padding-top: clamp(32px, 3vw, 56px); color: #f3f3ef; }
.fw-line { display: inline-block; white-space: nowrap; font-family: 'FL Wordmark', var(--font-sans); font-weight: 600; font-size: calc(min(100vw - var(--gutter) * 2, var(--container)) * .2); line-height: .8; letter-spacing: -.03em; }
.fw-ch { display: inline-block; will-change: transform; }
/* reduced-motion 的全局 transition-duration 会让 font-size 也过渡，fitWordmark 测宽时会拿到旧尺寸 */
.fw-line, .fw-ch { transition: none !important; }
.footer-bottom { margin-top: clamp(24px, 3vw, 44px); display: flex; flex-wrap: wrap; align-items: center; justify-content: space-between; gap: 14px 32px; font-size: 13px; }
.footer-copy { color: rgba(255, 255, 255, .55); }
.footer-ai-cta { display: inline-flex; align-items: center; gap: 8px; font-size: 13px; color: rgba(255, 255, 255, .72); transition: color var(--dur-1); }
.footer-ai-cta:hover { color: #fff; }
.footer-ai-cta .i { width: 15px; height: 15px; }
.footer-social { display: flex; align-items: center; gap: 20px; }
.footer-social a { color: rgba(255, 255, 255, .6); transition: color var(--dur-1); }
.footer-social a:hover { color: #fff; }
.footer-social .i { width: 18px; height: 18px; }
.footer-trust { display: flex; align-items: center; gap: 14px; }
.footer-trust img { width: auto; height: 30px; }
@media (max-width: 1280px) { .footer-grid { grid-template-columns: repeat(5, minmax(0, 1fr)); } }

.reveal { opacity: 0; transform: translateY(16px); transition: opacity var(--dur-4) var(--ease), transform var(--dur-4) var(--ease); }
.reveal.is-in { opacity: 1; transform: none; }
.reveal-mask { overflow: hidden; padding-block: .06em; margin-block: -.06em; }
.reveal-mask > * { display: block; transform: translateY(108%); transition: transform var(--dur-4) var(--ease); }
.reveal-mask.is-in > * { transform: none; }
[data-stagger] > * { opacity: 0; transform: translateY(14px); transition: opacity var(--dur-3) var(--ease), transform var(--dur-3) var(--ease); }
[data-stagger].is-in > * { opacity: 1; transform: none; }
[data-stagger].is-in > *:nth-child(1) { transition-delay: .04s; }
[data-stagger].is-in > *:nth-child(2) { transition-delay: .12s; }
[data-stagger].is-in > *:nth-child(3) { transition-delay: .2s; }
[data-stagger].is-in > *:nth-child(4) { transition-delay: .28s; }
[data-stagger].is-in > *:nth-child(5) { transition-delay: .36s; }
[data-stagger].is-in > *:nth-child(6) { transition-delay: .44s; }

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after { animation-duration: .01ms !important; animation-iteration-count: 1 !important; transition-duration: .01ms !important; }
  .reveal, [data-stagger] > *, .reveal-mask > * { opacity: 1 !important; transform: none !important; }
}

@media (max-width: 900px) {
  .nav-links { display: none; }
  .nav-burger { display: inline-flex; flex-direction: column; align-items: center; justify-content: center; margin-left: auto; }
  .nav-cta { margin-left: 0; }
  .nav-cta .btn--ghost, .nav-cta .nav-signin { display: none; }
  .footer-grid { grid-template-columns: repeat(3, minmax(0, 1fr)); }
}
@media (max-width: 560px) {
  .footer-grid { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .footer-cta-side { align-items: flex-start; }
  .footer-bottom { flex-direction: column; align-items: flex-start; }
  .footer-trust { flex-wrap: wrap; }
}