/* ============================================
   瑞泉水处理 - 响应式样式
   断点：1200 / 992 / 768 / 576
   ============================================ */

/* 大屏到中屏 (≤1200) */
@media (max-width: 1200px) {
  .container { padding: 0 20px; }
  :root { --header-height: 72px; }
  .brand-text, .brand-divider, .brand-sub { font-size: 19px; }
  .main-menu a { padding: 8px 12px; font-size: 14px; }
  .product-grid { grid-template-columns: repeat(3, 1fr); }
  .flow-grid { grid-template-columns: repeat(3, 1fr); }
  .flow-step::after { display: none; }
  .city-list { grid-template-columns: repeat(5, 1fr); }
}

/* 中屏 (≤992) */
@media (max-width: 992px) {
  :root { --header-height: 64px; }
  .top-nav { gap: 12px; }
  .brand-text, .brand-divider, .brand-sub { font-size: 17px; }
  .brand-logo { width: 40px; height: 40px; }
  .brand-logo svg { width: 30px; height: 30px; }
  .header-phone { display: none; }
  .main-menu {
    position: absolute;
    top: var(--header-height);
    left: 0; right: 0;
    flex-direction: column;
    background: rgba(10, 74, 126, 0.98);
    padding: 16px 20px;
    gap: 4px;
    align-items: stretch;
    display: none;
    backdrop-filter: blur(8px);
    border-top: 1px solid rgba(255, 255, 255, 0.1);
  }
  .main-menu.open { display: flex; }
  .main-menu a {
    padding: 12px 16px;
    text-align: left;
    border-radius: 8px;
  }
  .menu-toggle { display: inline-flex; align-items: center; gap: 6px; }
  .menu-toggle svg { width: 16px; height: 16px; }

  .hero { padding: 60px 0 80px; }
  .hero-stats { grid-template-columns: repeat(2, 1fr); gap: 12px; }
  .hero-stat { padding: 18px 10px; }

  .biz-grid, .biz-grid-extra { grid-template-columns: repeat(2, 1fr); }
  .advantage-grid { grid-template-columns: repeat(2, 1fr); }
  .app-grid { grid-template-columns: repeat(3, 1fr); }
  .sister-grid { grid-template-columns: repeat(2, 1fr); }

  .about-wrap { grid-template-columns: 1fr; gap: 32px; }
  .about-visual { max-width: 480px; margin: 0 auto; }

  .contact-wrap { grid-template-columns: 1fr; padding: 28px; }

  .city-list { grid-template-columns: repeat(4, 1fr); }
  section { padding: 60px 0; }
  .section-head { margin-bottom: 40px; }
}

/* 平板 (≤768) */
@media (max-width: 768px) {
  .container { padding: 0 16px; }
  body { font-size: 15px; }
  .hero h1 { font-size: 28px; line-height: 1.4; }
  .hero-sub { font-size: 14.5px; }
  .hero-actions { flex-direction: column; align-items: stretch; }
  .hero-actions .btn { justify-content: center; }

  .product-grid { grid-template-columns: repeat(2, 1fr); gap: 14px; }
  .flow-grid { grid-template-columns: repeat(2, 1fr); }
  .app-grid { grid-template-columns: repeat(2, 1fr); }
  .sister-grid { grid-template-columns: 1fr; }
  .city-list { grid-template-columns: repeat(3, 1fr); }
  .biz-grid, .biz-grid-extra { grid-template-columns: 1fr; }
  .advantage-grid { grid-template-columns: 1fr 1fr; }
  .about-list { grid-template-columns: 1fr; }

  .footer-top { flex-direction: column; align-items: center; gap: 8px; text-align: center; }
  .footer-divider { display: none; }

  section { padding: 48px 0; }
}

/* 手机 (≤576) */
@media (max-width: 576px) {
  .brand-text { font-size: 15px; }
  .brand-divider { margin: 0 8px; font-size: 16px; }
  .brand-sub { font-size: 15px; }
  .brand { gap: 8px; }
  .brand-logo { width: 36px; height: 36px; }
  .brand-logo svg { width: 26px; height: 26px; }

  .hero { padding: 40px 0 60px; }
  .hero-eyebrow { font-size: 12px; padding: 5px 12px; }
  .hero h1 { font-size: 24px; }
  .hero-sub { font-size: 13.5px; line-height: 1.7; }
  .hero-stats { grid-template-columns: 1fr 1fr; gap: 10px; }
  .hero-stat { padding: 14px 8px; }
  .hero-stat-num { font-size: 22px; }
  .hero-stat-label { font-size: 11.5px; }

  .product-grid { grid-template-columns: 1fr 1fr; gap: 10px; }
  .product-name { font-size: 13.5px; min-height: 40px; }
  .product-desc { font-size: 12px; }
  .product-info { padding: 12px; }
  .product-tab { font-size: 12.5px; padding: 6px 12px; }

  .city-list { grid-template-columns: repeat(2, 1fr); }
  .flow-grid { grid-template-columns: 1fr; }

  .contact-wrap { padding: 20px; }
  .contact-item-value.phone { font-size: 18px; }
  .contact-qr img { width: 130px; height: 130px; }

  section { padding: 40px 0; }
  .section-head h2 { font-size: 22px; }
  .section-eyebrow { font-size: 12px; letter-spacing: 2px; }

  .footer-copy { font-size: 12.5px; padding: 16px 12px 0; }
}

/* 大屏 (≥1400) */
@media (min-width: 1400px) {
  :root { --header-height: 88px; }
  .brand-text, .brand-divider, .brand-sub { font-size: 24px; }
  .brand-logo { width: 52px; height: 52px; }
  .brand-logo svg { width: 40px; height: 40px; }
  .main-menu a { font-size: 16px; padding: 10px 18px; }
  .hero { padding: 100px 0 120px; }
  .container { padding: 0 32px; }
}