:root {
  --primary: #1d1d1f;
  --accent: #ff6b35;
  --bg: #f2f2f0;
  --surface: #ffffff;
  --ink: #111111;
  --muted: #5c5c5c;
  --line: #d9d9d4;
  --max: 1120px;
  --radius: 2px;
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  background: var(--bg);
  color: var(--ink);
  font-family: -apple-system, BlinkMacSystemFont, "PingFang SC", "Microsoft YaHei", "Noto Sans SC", sans-serif;
  font-size: 16px;
  line-height: 1.75;
  -webkit-font-smoothing: antialiased;
}

a {
  color: inherit;
  text-decoration: none;
}

h1, h2, h3 {
  margin: 0;
  font-weight: 600;
  line-height: 1.2;
  letter-spacing: -0.02em;
}

p {
  margin: 0 0 1.1em;
}

/* ---------- 顶部导航 ---------- */
.site-header {
  position: sticky;
  top: 0;
  z-index: 50;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 24px;
  max-width: var(--max);
  margin: 0 auto;
  padding: 20px 28px;
  background: rgba(242, 242, 240, 0.92);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid transparent;
}

.site-header.is-scrolled {
  border-bottom-color: var(--line);
}

.brand {
  display: inline-flex;
  align-items: center;
}

.brand-logo {
  display: block;
  height: 44px;
  width: auto;
}

.nav {
  display: flex;
  gap: 28px;
  font-size: 14px;
}

.nav a {
  position: relative;
  padding: 4px 0;
  color: var(--muted);
  transition: color 0.2s ease;
}

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

.nav a::after {
  content: "";
  position: absolute;
  left: 0;
  bottom: 0;
  width: 0;
  height: 1px;
  background: var(--accent);
  transition: width 0.25s ease;
}

.nav a:hover::after {
  width: 100%;
}

.nav-toggle {
  display: none;
  width: 40px;
  height: 40px;
  padding: 10px;
  background: none;
  border: 1px solid var(--line);
  cursor: pointer;
}

.nav-toggle span {
  display: block;
  height: 1px;
  margin: 5px 0;
  background: var(--ink);
}

/* ---------- 通用区块 ---------- */
.section {
  max-width: var(--max);
  margin: 0 auto;
  padding: 100px 28px;
}

.section-alt {
  max-width: none;
  background: var(--surface);
}

.section-alt > * {
  max-width: var(--max);
  margin-left: auto;
  margin-right: auto;
}

.section-head {
  margin-bottom: 52px;
}

.section-head h2 {
  font-size: clamp(30px, 4.5vw, 48px);
}

.section-desc {
  max-width: 560px;
  margin-top: 16px;
  color: var(--muted);
}

.prose {
  max-width: 780px;
  font-size: 16px;
  color: #262626;
}

.prose p:last-child {
  margin-bottom: 0;
}

.eyebrow {
  margin: 0 0 22px;
  font-size: 11px;
  font-weight: 600;
  letter-spacing: 0.28em;
  color: var(--accent);
  text-transform: uppercase;
}

.num {
  display: block;
  margin-bottom: 16px;
  font-size: 11px;
  font-weight: 600;
  letter-spacing: 0.2em;
  color: var(--accent);
}

/* ---------- 页脚 ---------- */
.site-footer {
  background: var(--primary);
  color: #d8d8d4;
}

.footer-inner {
  max-width: var(--max);
  margin: 0 auto;
  padding: 52px 28px;
  font-size: 13px;
}

.footer-inner p {
  margin: 0 0 8px;
}

.footer-brand {
  margin-bottom: 18px !important;
  color: #fff;
  font-size: 15px;
  letter-spacing: 0.06em;
}

/* ---------- 滚动显现 ---------- */
.reveal {
  opacity: 0;
  transform: translateY(18px);
  transition: opacity 0.6s ease, transform 0.6s ease;
}

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

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