/* ===== 隙间 XiJian 官网 · Apple 风格 ===== */
:root {
  --bg: #000;
  --bg-alt: #0a0a0c;
  --surface: #131316;
  --surface-hover: #1b1b1f;
  --border: rgba(255, 255, 255, 0.1);
  --border-strong: rgba(255, 255, 255, 0.18);
  --text: #f5f5f7;
  --text-dim: #a1a1a6;
  --text-faint: #6e6e73;
  --accent: #8b7cf6;
  --font: -apple-system, BlinkMacSystemFont, "SF Pro SC", "PingFang SC",
    "Hiragino Sans GB", "Microsoft YaHei", "Noto Sans SC", sans-serif;
}

* { margin: 0; padding: 0; box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
  font-family: var(--font);
  background: var(--bg);
  color: var(--text);
  line-height: 1.6;
  font-size: 16px;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
  overflow-x: hidden;
}

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

.sr-only {
  position: absolute;
  width: 1px; height: 1px;
  margin: -1px;
  padding: 0;
  overflow: hidden;
  clip: rect(0 0 0 0);
  white-space: nowrap;
  border: 0;
}

.card-note {
  margin-top: 12px;
  padding-top: 12px;
  border-top: 1px solid var(--border);
  font-size: 12px;
  color: var(--text-faint);
  line-height: 1.6;
}

.container { max-width: 980px; margin: 0 auto; padding: 0 24px; }

/* ===== 按钮 ===== */
.btn {
  display: inline-block;
  padding: 12px 26px;
  border-radius: 980px;
  font-size: 16px;
  font-weight: 500;
  letter-spacing: 0.01em;
  border: 1px solid transparent;
  cursor: pointer;
  transition: background 0.2s ease, color 0.2s ease, border-color 0.2s ease;
}
.btn:active { transform: scale(0.97); }
.btn-primary {
  background: var(--text);
  color: #000;
}
.btn-primary:hover { background: #ffffff; }
.btn-secondary {
  background: transparent;
  color: var(--text);
  border-color: var(--border-strong);
}
.btn-secondary:hover { background: rgba(255, 255, 255, 0.08); }
.btn-sm { padding: 9px 20px; font-size: 14px; }

/* ===== 导航 ===== */
.nav {
  position: fixed;
  top: 0; left: 0; right: 0;
  z-index: 100;
  background: transparent;
  transition: background 0.3s ease, border-color 0.3s ease;
  border-bottom: 1px solid transparent;
}
.nav.scrolled {
  background: rgba(0, 0, 0, 0.72);
  -webkit-backdrop-filter: blur(20px) saturate(180%);
  backdrop-filter: blur(20px) saturate(180%);
  border-bottom-color: rgba(255, 255, 255, 0.08);
}
.nav-inner {
  max-width: 980px;
  margin: 0 auto;
  padding: 0 24px;
  height: 52px;
  display: flex;
  align-items: center;
  justify-content: space-between;
}
.brand { display: flex; align-items: center; gap: 9px; }
.brand-mark { width: 22px; height: 22px; border-radius: 6px; color: var(--text); display: block; }
.brand-text { font-size: 17px; font-weight: 600; letter-spacing: 0.02em; }
.nav-links { display: flex; align-items: center; gap: 28px; font-size: 14px; }
.nav-links a { color: var(--text-dim); transition: color 0.2s ease; }
.nav-links a:hover { color: var(--text); }
.nav-toggle {
  display: none;
  flex-direction: column;
  gap: 5px;
  background: none;
  border: none;
  cursor: pointer;
  padding: 6px;
}
.nav-toggle span {
  width: 18px; height: 1.5px;
  background: var(--text);
  border-radius: 1px;
  transition: transform 0.25s ease, opacity 0.25s ease;
}

/* ===== Hero ===== */
.hero {
  min-height: 92vh;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  text-align: center;
  padding: 140px 24px 100px;
}
.hero-eyebrow {
  font-size: 14px;
  font-weight: 500;
  letter-spacing: 0.04em;
  color: var(--text-dim);
  margin-bottom: 24px;
}
.hero-title {
  font-size: clamp(64px, 12vw, 110px);
  font-weight: 700;
  letter-spacing: -0.03em;
  line-height: 1.05;
  margin-bottom: 28px;
  color: var(--text);
}
.hero-sub {
  font-size: clamp(16px, 2.2vw, 19px);
  color: var(--text-dim);
  line-height: 1.7;
  margin-bottom: 44px;
}
.hero-actions { display: flex; gap: 14px; justify-content: center; flex-wrap: wrap; }
.hero-note { margin-top: 44px; font-size: 13px; color: var(--text-faint); }

/* ===== 通用区块 ===== */
.section { padding: 110px 0; }
.section-tight { padding: 60px 0; }
.section-alt { background: var(--bg-alt); }
.section-title {
  font-size: clamp(30px, 4.5vw, 44px);
  font-weight: 650;
  letter-spacing: -0.02em;
  line-height: 1.15;
  text-align: center;
  margin-bottom: 12px;
}
.section-desc { text-align: center; color: var(--text-dim); margin-bottom: 64px; font-size: 17px; }

/* ===== 理念 ===== */
.philosophy {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 48px;
}
.philosophy-item h3 {
  font-size: 20px;
  font-weight: 600;
  letter-spacing: -0.01em;
  margin-bottom: 10px;
}
.philosophy-item p { font-size: 14.5px; color: var(--text-dim); line-height: 1.7; }

/* ===== 功能卡片 ===== */
.cards { display: grid; grid-template-columns: repeat(3, 1fr); gap: 20px; }
.card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 20px;
  padding: 30px 26px;
  transition: background 0.25s ease, border-color 0.25s ease;
}
.card:hover { background: var(--surface-hover); border-color: var(--border-strong); }
.card-icon {
  width: 30px; height: 30px;
  color: var(--accent);
  margin-bottom: 18px;
}
.card h3 { font-size: 17px; font-weight: 600; margin-bottom: 8px; letter-spacing: -0.01em; }
.card p { font-size: 14px; color: var(--text-dim); line-height: 1.65; }

/* ===== 平台 ===== */
.platforms {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 20px;
}
.platform {
  border: 1px solid var(--border);
  border-radius: 20px;
  padding: 34px 28px;
  text-align: center;
  background: var(--surface);
  transition: background 0.25s ease, border-color 0.25s ease;
}
.platform:hover { background: var(--surface-hover); border-color: var(--border-strong); }
.platform h3 { font-size: 19px; font-weight: 600; margin-bottom: 10px; }
.platform p { font-size: 13.5px; color: var(--text-dim); line-height: 1.8; }

/* ===== 开发组 ===== */
.about-text {
  max-width: 560px;
  margin: 0 auto 40px;
  text-align: center;
}
.about-text p {
  font-size: 15px;
  color: var(--text-dim);
  line-height: 1.8;
}
.about-links { display: flex; gap: 14px; justify-content: center; flex-wrap: wrap; }

/* ===== 加入我们 ===== */
.join-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 20px; }
.join-card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 20px;
  padding: 32px 28px;
  display: flex;
  flex-direction: column;
  gap: 14px;
  transition: background 0.25s ease, border-color 0.25s ease;
}
.join-card:hover { background: var(--surface-hover); border-color: var(--border-strong); }
.join-card h3 { font-size: 19px; font-weight: 600; letter-spacing: -0.01em; }
.join-card p { font-size: 14px; color: var(--text-dim); line-height: 1.65; flex: 1; }
.join-qq { font-size: 13.5px; }
.qq-num { color: var(--text); font-weight: 500; }
.copy-btn {
  margin-left: 6px;
  padding: 2px 10px;
  font-size: 12px;
  font-family: inherit;
  color: var(--text-dim);
  background: transparent;
  border: 1px solid var(--border);
  border-radius: 980px;
  cursor: pointer;
  transition: color 0.2s ease, border-color 0.2s ease, background 0.2s ease;
}
.copy-btn:hover { color: var(--text); border-color: var(--border-strong); background: rgba(255, 255, 255, 0.06); }
.copy-btn.copied { color: #6ee7b7; border-color: rgba(110, 231, 183, 0.4); }
.join-card .btn { align-self: flex-start; }

/* ===== 声明 ===== */
.disclaimer {
  max-width: 720px;
  margin: 0 auto;
  text-align: left;
}
.disclaimer h3 {
  font-size: 13px;
  font-weight: 600;
  letter-spacing: 0.04em;
  text-transform: uppercase;
  color: var(--text-faint);
  margin-bottom: 14px;
}
.disclaimer ul { list-style: none; display: flex; flex-direction: column; gap: 8px; }
.disclaimer li {
  font-size: 13px;
  color: var(--text-faint);
  line-height: 1.7;
  padding-left: 14px;
  position: relative;
}
.disclaimer li::before {
  content: "";
  position: absolute;
  left: 0; top: 0.62em;
  width: 4px; height: 4px;
  border-radius: 50%;
  background: var(--text-faint);
}

/* ===== 页脚 ===== */
.footer {
  border-top: 1px solid var(--border);
  padding: 44px 24px;
  text-align: center;
  color: var(--text-faint);
  font-size: 13.5px;
}
.footer p { margin-bottom: 6px; }
.footer a { color: var(--text-dim); transition: color 0.2s ease; }
.footer a:hover { color: var(--text); }
.footer-meta { font-size: 12px; opacity: 0.8; }

/* ===== 响应式 ===== */
@media (max-width: 860px) {
  .philosophy, .cards, .platforms, .join-grid { grid-template-columns: 1fr; }
  .section { padding: 80px 0; }
  .nav-toggle { display: flex; }
  .nav-links {
    position: absolute;
    top: 100%; left: 0; right: 0;
    flex-direction: column;
    align-items: flex-start;
    gap: 0;
    background: rgba(0, 0, 0, 0.92);
    -webkit-backdrop-filter: blur(20px);
    backdrop-filter: blur(20px);
    border-bottom: 1px solid var(--border);
    padding: 0 24px;
    max-height: 0;
    overflow: hidden;
    visibility: hidden;
    transition: max-height 0.3s ease, visibility 0.3s ease;
  }
  .nav-links.open { max-height: 340px; padding: 10px 24px 18px; visibility: visible; }
  .nav-links a { padding: 12px 0; width: 100%; font-size: 16px; }
}

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  .btn, .card, .team-card, .join-card, .platform, .nav, .nav-links { transition: none; }
  .btn:active { transform: none; }
}

@media (prefers-reduced-transparency: reduce) {
  .nav.scrolled, .nav-links { background: #000; -webkit-backdrop-filter: none; backdrop-filter: none; }
}