/* === SHARED DESIGN SYSTEM · Warm Paper + Sage Green === */
/* 品牌套件 brand-kit.html 是颜色/字体/间距的唯一真相源 */

/* === CSS VARIABLES === */
:root {
  --paper:      #F5F0EB;
  --ink:        #3A3A35;
  --ink-dark:   #2D3436;
  --grey-1:     #EDE8DC;
  --grey-2:     #DDD8CB;
  --grey-3:     #888888;
  --accent:     #6B8F71;
  --accent-soft: rgba(107,143,113,0.12);
  --accent-mid:  rgba(107,143,113,0.18);
  --rule:       #E5DFCE;
  --rule-light: rgba(0,0,0,0.04);
  --sans:       "Inter","Helvetica Neue","Helvetica","Arial",system-ui,sans-serif;
  --sans-zh:    "PingFang SC","Hiragino Sans GB","Source Han Sans SC","Noto Sans SC","Microsoft YaHei UI",sans-serif;
  --serif:      "Noto Serif SC","Source Han Serif SC","Songti SC","SimSun",serif;
  --mono:       "JetBrains Mono","IBM Plex Mono","SF Mono","Cascadia Code","Consolas",ui-monospace,monospace;
  --wmax:       1200px;
  --pad:        48px;
}

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

body {
  background: var(--paper);
  font-family: var(--sans), var(--sans-zh);
  font-weight: 400;
  color: var(--ink);
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

/* === NAV === */
#nav {
  position: sticky; top: 0; z-index: 100;
  background: rgba(245,240,235,0.88);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--rule);
  padding: 0 var(--pad);
  height: 56px;
  display: flex; align-items: center; justify-content: space-between;
}
#nav .logo {
  font-family: var(--mono);
  font-size: 13px; font-weight: 600;
  letter-spacing: 0.06em;
}
#nav .logo a {
  color: var(--accent); text-decoration: none;
}
#nav .nav-links {
  display: flex; gap: 28px;
  font-size: 14px; font-weight: 450;
}
#nav .nav-links a {
  color: var(--ink); text-decoration: none;
  transition: color 0.15s;
}
#nav .nav-links a:hover { color: var(--accent); }
#nav .nav-links a.active { color: var(--accent); }

/* === HAMBURGER === */
#hamburger {
  display: none;
  background: none; border: none; cursor: pointer;
  width: 36px; height: 36px;
  padding: 8px 6px;
  flex-direction: column; justify-content: center; gap: 4px;
}
#hamburger span {
  display: block; width: 100%; height: 2px;
  background: var(--ink); border-radius: 1px;
  transition: transform 0.25s, opacity 0.25s;
}
#hamburger.open span:nth-child(1) { transform: translateY(6px) rotate(45deg); }
#hamburger.open span:nth-child(2) { opacity: 0; }
#hamburger.open span:nth-child(3) { transform: translateY(-6px) rotate(-45deg); }

/* === RESPONSIVE NAV === */
@media (max-width: 640px) {
  :root { --pad: 20px; }
  #nav { height: 48px; }
  #hamburger { display: flex; }
  #nav .nav-links {
    display: none;
    position: absolute; top: 48px; left: 0; right: 0;
    background: rgba(245,240,235,0.95);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    border-bottom: 1px solid var(--rule);
    padding: 16px var(--pad);
    flex-direction: column; gap: 12px;
  }
  #nav .nav-links.open { display: flex; }
}

/* === SECTION DIVIDER === */
.section-divider {
  border: none;
  border-top: 1px solid var(--rule);
  margin: 0 var(--pad);
}