/* =============================================================================
   第二本能 (Second Nature) — 公共样式
   ============================================================================= */

:root {
  --color-fg: #1d1d1f;
  --color-fg-muted: #6e6e73;
  --color-bg: #ffffff;
  --color-bg-soft: #f5f5f7;
  --color-border: #d2d2d7;
  --color-accent: #0071e3;
  --color-accent-hover: #0077ed;
  --max-width: 720px;
}

* {
  box-sizing: border-box;
}

html, body {
  margin: 0;
  padding: 0;
  font-family: -apple-system, BlinkMacSystemFont, "PingFang SC", "Hiragino Sans GB",
               "Microsoft YaHei", "Helvetica Neue", Helvetica, Arial, sans-serif;
  font-size: 16px;
  line-height: 1.6;
  color: var(--color-fg);
  background: var(--color-bg);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

body {
  display: flex;
  flex-direction: column;
  min-height: 100vh;
}

/* ---------- 顶部品牌栏 ---------- */
.site-header {
  padding: 18px 24px;
  border-bottom: 1px solid var(--color-border);
}
.site-header-inner {
  max-width: var(--max-width);
  margin: 0 auto;
  display: flex;
  align-items: center;
  justify-content: space-between;
}
.brand {
  font-size: 18px;
  font-weight: 600;
  color: var(--color-fg);
  text-decoration: none;
}
.brand-en {
  font-size: 13px;
  color: var(--color-fg-muted);
  margin-left: 8px;
}

/* ---------- 主内容区 ---------- */
main {
  flex: 1;
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 32px 24px;
  width: 100%;
}

main h1 {
  font-size: 32px;
  font-weight: 700;
  margin: 0 0 8px;
  letter-spacing: -0.02em;
}
main h2 {
  font-size: 22px;
  font-weight: 600;
  margin: 32px 0 12px;
  letter-spacing: -0.01em;
}
main h3 {
  font-size: 18px;
  font-weight: 600;
  margin: 24px 0 8px;
}
main p {
  margin: 0 0 16px;
  color: var(--color-fg);
}
main ul, main ol {
  margin: 0 0 16px;
  padding-left: 24px;
}
main li {
  margin-bottom: 6px;
}
.lead {
  font-size: 18px;
  color: var(--color-fg-muted);
  margin-bottom: 32px;
}
.placeholder {
  background: #fff7e6;
  border-left: 3px solid #faad14;
  padding: 8px 12px;
  margin: 8px 0;
  font-size: 14px;
  color: #874d00;
  border-radius: 0 4px 4px 0;
}
.muted {
  color: var(--color-fg-muted);
  font-size: 14px;
}

/* ---------- 着陆页 hero ---------- */
.hero {
  text-align: center;
  padding: 64px 24px 48px;
  background: linear-gradient(180deg, var(--color-bg-soft) 0%, var(--color-bg) 100%);
}
.hero h1 {
  font-size: 44px;
  margin-bottom: 16px;
}
.hero .lead {
  font-size: 20px;
  margin: 0 auto 32px;
  max-width: 540px;
}
.hero-en {
  display: block;
  font-size: 16px;
  color: var(--color-fg-muted);
  font-weight: 400;
  margin-top: 6px;
  letter-spacing: 0;
}

/* ---------- 按钮 ---------- */
.btn {
  display: inline-block;
  padding: 12px 28px;
  border-radius: 999px;
  font-size: 16px;
  font-weight: 500;
  text-decoration: none;
  transition: background 0.15s ease;
  border: none;
  cursor: pointer;
}
.btn-primary {
  background: var(--color-accent);
  color: #fff;
}
.btn-primary:hover {
  background: var(--color-accent-hover);
}
.btn-secondary {
  background: var(--color-bg-soft);
  color: var(--color-fg);
}

/* ---------- 卡片 ---------- */
.feature-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: 24px;
  margin: 48px 0;
}
.feature-card {
  background: var(--color-bg-soft);
  padding: 24px;
  border-radius: 12px;
}
.feature-card h3 {
  margin-top: 0;
}

/* ---------- 链接 ---------- */
a {
  color: var(--color-accent);
  text-decoration: none;
}
a:hover {
  text-decoration: underline;
}

/* ---------- 底部 ---------- */
.site-footer {
  border-top: 1px solid var(--color-border);
  padding: 24px;
  margin-top: 48px;
  font-size: 14px;
  color: var(--color-fg-muted);
  background: var(--color-bg-soft);
}
.site-footer-inner {
  max-width: var(--max-width);
  margin: 0 auto;
  display: flex;
  flex-wrap: wrap;
  justify-content: space-between;
  gap: 16px;
}
.site-footer nav {
  display: flex;
  flex-wrap: wrap;
  gap: 16px;
}
.site-footer a {
  color: var(--color-fg-muted);
}
.site-footer a:hover {
  color: var(--color-fg);
}

/* ---------- 移动端微调 ---------- */
@media (max-width: 600px) {
  .hero { padding: 48px 24px 32px; }
  .hero h1 { font-size: 32px; }
  .hero .lead { font-size: 17px; }
  main h1 { font-size: 26px; }
  main h2 { font-size: 19px; }
  .site-footer-inner { flex-direction: column; }
}