/* 基础布局工具类（替代 Tailwind CDN，国内可离线使用） */
*,
*::before,
*::after { box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
  margin: 0;
  min-height: 100vh;
  font-family:
    -apple-system, BlinkMacSystemFont,
    "Segoe UI", "Segoe UI Variable",
    "PingFang SC", "Hiragino Sans GB",
    "Microsoft YaHei UI", "Microsoft YaHei",
    "Helvetica Neue", Helvetica, Arial,
    "Noto Sans SC", sans-serif;
  font-size: 16px;
  line-height: 1.5;
  color: var(--brand-ink);
  background: var(--brand-cream);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

a { color: inherit; text-decoration: none; }
img { max-width: 100%; height: auto; }
button, input { font: inherit; }

.mx-auto { margin-left: auto; margin-right: auto; }
.max-w-3xl { max-width: 48rem; }
.max-w-4xl { max-width: 56rem; }
.max-w-5xl { max-width: 64rem; }
.max-w-6xl { max-width: 72rem; }
.max-w-xl { max-width: 36rem; }

.px-4 { padding-left: 1rem; padding-right: 1rem; }
.py-4 { padding-top: 1rem; padding-bottom: 1rem; }
.py-6 { padding-top: 1.5rem; padding-bottom: 1.5rem; }
.py-10 { padding-top: 2.5rem; padding-bottom: 2.5rem; }
.pt-4 { padding-top: 1rem; }
.pt-10 { padding-top: 2.5rem; }
.pt-12 { padding-top: 3rem; }
.pb-4 { padding-bottom: 1rem; }
.pb-6 { padding-bottom: 1.5rem; }
.pb-8 { padding-bottom: 2rem; }
.pb-16 { padding-bottom: 4rem; }
.p-4 { padding: 1rem; }

.mt-1 { margin-top: 0.25rem; }
.mt-2 { margin-top: 0.5rem; }
.mt-3 { margin-top: 0.75rem; }
.mt-4 { margin-top: 1rem; }
.mt-5 { margin-top: 1.25rem; }
.mt-6 { margin-top: 1.5rem; }
.mt-8 { margin-top: 2rem; }
.mt-10 { margin-top: 2.5rem; }
.mt-12 { margin-top: 3rem; }
.mt-20 { margin-top: 5rem; }
.mb-3 { margin-bottom: 0.75rem; }
.mb-4 { margin-bottom: 1rem; }
.mb-6 { margin-bottom: 1.5rem; }
.mx-1 { margin-left: 0.25rem; margin-right: 0.25rem; }

.flex { display: flex; }
.inline-flex { display: inline-flex; }
.flex-col { flex-direction: column; }
.flex-wrap { flex-wrap: wrap; }
.flex-1 { flex: 1 1 0%; }
.items-center { align-items: center; }
.items-start { align-items: flex-start; }
.items-end { align-items: flex-end; }
.justify-between { justify-content: space-between; }
.justify-center { justify-content: center; }
.gap-1 { gap: 0.25rem; }
.gap-2 { gap: 0.5rem; }
.gap-3 { gap: 0.75rem; }
.gap-4 { gap: 1rem; }
.gap-6 { gap: 1.5rem; }
.min-w-0 { min-width: 0; }
.shrink-0 { flex-shrink: 0; }
.relative { position: relative; }
.sticky { position: sticky; }
.top-0 { top: 0; }
.z-10 { z-index: 10; }
.z-50 { z-index: 50; }
.text-center { text-align: center; }
.w-9 { width: 2.25rem; }
.h-9 { height: 2.25rem; }
.h-16 { height: 4rem; }

.text-xs { font-size: 0.75rem; line-height: 1rem; }
.text-sm { font-size: 0.875rem; line-height: 1.25rem; }
.text-base { font-size: 1rem; line-height: 1.5rem; }
.text-lg { font-size: 1.125rem; line-height: 1.75rem; }
.text-xl { font-size: 1.25rem; line-height: 1.75rem; }
.text-2xl { font-size: 1.5rem; line-height: 2rem; }
.text-3xl { font-size: 1.875rem; line-height: 2.25rem; }
.font-medium { font-weight: 500; }
.font-bold { font-weight: 700; }
.font-black { font-weight: 900; }
.leading-tight { line-height: 1.25; }
.leading-relaxed { line-height: 1.625; }
.tracking-tight { letter-spacing: -0.025em; }
.whitespace-nowrap { white-space: nowrap; }

.text-brand-ink { color: var(--brand-ink); }
.text-brand-orange { color: var(--brand-orange); }
.bg-brand-cream { background-color: var(--brand-cream); }
.text-black\/40 { color: rgba(26, 18, 11, 0.4); }
.text-black\/45 { color: rgba(26, 18, 11, 0.45); }
.text-black\/50 { color: rgba(26, 18, 11, 0.5); }
.text-black\/55 { color: rgba(26, 18, 11, 0.55); }
.text-black\/60 { color: rgba(26, 18, 11, 0.6); }
.text-black\/65 { color: rgba(26, 18, 11, 0.65); }
.text-black\/70 { color: rgba(26, 18, 11, 0.7); }
.hover\:text-brand-orange:hover { color: var(--brand-orange); }
.hover\:underline:hover { text-decoration: underline; }

.border-t { border-top: 1px solid rgba(26, 18, 11, 0.05); }
.scroll-mt-24 { scroll-margin-top: 6rem; }
.space-y-2 > * + * { margin-top: 0.5rem; }
.space-y-3 > * + * { margin-top: 0.75rem; }
.space-y-8 > * + * { margin-top: 2rem; }
.space-y-10 > * + * { margin-top: 2.5rem; }

/* JS 显隐：勿用于响应式导航 */
.is-hidden,
.u-hidden { display: none !important; }

/* PC / 移动导航（不依赖 Tailwind） */
.nav-desktop { display: none; }
.nav-mobile-btn { display: inline-flex; }
.header-cta-desktop { display: none; }
.mobile-nav { display: none; }
.mobile-nav.is-open { display: grid; }

@media (min-width: 768px) {
  .nav-desktop { display: flex; }
  .nav-mobile-btn { display: none !important; }
  .header-cta-desktop { display: inline-flex; }
  .mobile-nav,
  .mobile-nav.is-open { display: none !important; }
  .sm\:text-lg { font-size: 1.125rem; line-height: 1.75rem; }
  .sm\:text-3xl { font-size: 1.875rem; line-height: 2.25rem; }
  .sm\:text-4xl { font-size: 2.25rem; line-height: 2.5rem; }
  .sm\:text-5xl { font-size: 3rem; line-height: 1; }
  .sm\:pt-14 { padding-top: 3.5rem; }
  .sm\:pb-10 { padding-bottom: 2.5rem; }
  .sm\:flex-row { flex-direction: row; }
  .sm\:items-end { align-items: flex-end; }
  .sm\:items-center { align-items: center; }
  .sm\:justify-between { justify-content: space-between; }
}

@media (min-width: 640px) {
  .sm\:inline-flex { display: inline-flex; }
}

.brand-mark:hover span { color: var(--brand-orange); }
.bg-white\/60 { background: rgba(255, 255, 255, 0.6); }