/* ==============================================
   响应式适配
   ============================================== */

/* 汉堡菜单按钮（默认隐藏） */
.menu-toggle { display: none; background: none; border: none; cursor: pointer; padding: 8px; }
.menu-toggle span { display: block; width: 24px; height: 3px; background: #1a5276; border-radius: 2px; margin: 4px 0; transition: all 0.3s; }
.menu-toggle.active span:nth-child(1) { transform: rotate(45deg) translate(5px, 5px); }
.menu-toggle.active span:nth-child(2) { opacity: 0; }
.menu-toggle.active span:nth-child(3) { transform: rotate(-45deg) translate(7px, -7px); }

@media (max-width: 1024px) {
    .container { padding: 0 15px; }
    .header-main .container { flex-wrap: wrap; gap: 15px; }
    .header-search { order: 3; flex: 1 1 100%; }
    .compact-two-col { grid-template-columns: 1fr; }
    .product-grid { grid-template-columns: repeat(3, 1fr); }
    .footer-grid { grid-template-columns: repeat(2, 1fr); }
    .detail-main { grid-template-columns: 1fr; }
    .detail-img-box { max-width: 400px; }
    .features-grid { grid-template-columns: repeat(2, 1fr); }
    .hvac-features-grid { grid-template-columns: repeat(2, 1fr); }
    .flow-steps { flex-wrap: wrap; }
    .flow-arrow { display: none; }
    .category-children { grid-template-columns: repeat(4, 1fr); }
    .engineering-cate-sidebar { width: 170px; }

    .stats-grid { grid-template-columns: repeat(3, 1fr); }
    .eng-cate-product-grid { grid-template-columns: repeat(3, 1fr); }
    .platform-services-list { grid-template-columns: repeat(3, 1fr); }
    .member-levels-grid { grid-template-columns: 1fr; }
    .guarantee-grid { grid-template-columns: repeat(2, 1fr); }
    .article-grid { grid-template-columns: repeat(2, 1fr); }
    .merchant-grid { grid-template-columns: repeat(2, 1fr); }
    .hvac-modules-grid { grid-template-columns: repeat(2, 1fr); }
    .examples-grid { grid-template-columns: repeat(2, 1fr); }
}

/* 移动端顶部登录注册按钮区（默认隐藏，移动端显示） */
.header-user-mobile { display: none; align-items: center; gap: 8px; }
.header-user-mobile-btn {
    display: inline-flex; align-items: center; justify-content: center;
    padding: 6px 14px; font-size: 13px; border-radius: 4px;
    text-decoration: none; white-space: nowrap; line-height: 1.4; cursor: pointer;
}
.header-user-mobile-login { background: #1a5276; color: #fff; border: none; }
.header-user-mobile-register { background: #fff; color: #1a5276; border: 1px solid #1a5276; }
.header-user-mobile-logout { background: #fff; color: #c0392b; border: 1px solid #c0392b; }

@media (max-width: 768px) {
    .header-top { display: none; }
    .menu-toggle { display: block; order: 3; }
    .header-user-mobile { display: flex; order: 2; margin-left: auto; }
    .header-search { order: 4; }
    .header-nav { display: none; flex-direction: column; gap: 0; order: 5; flex: 1 1 100%; }
    .header-nav.active { display: flex; }
    .header-nav .nav-link { padding: 12px 0; border-bottom: 1px solid #f0f0f0; }
    .header-nav .nav-user-menu { display: none; }
    .header-category { display: none; }
    .logo-text { font-size: 20px; }
    .logo-img { height: 42px; }
    .hero-wrapper { flex-direction: column; }
    .engineering-cate-sidebar { width: 100%; }
    .engineering-cate-list { display: flex; flex-wrap: wrap; }
    .engineering-cate-item { flex: 1 1 33.33%; border-bottom: none; border-right: 1px solid #f5f5f5; }
    .engineering-cate-item a { padding: 8px 10px; }
    .banner-wrapper { height: 250px; }
    .eng-other-cate-grid { grid-template-columns: repeat(3, 1fr); }
    .eng-page-header { padding: 25px 15px; }
    .eng-page-icon { width: 60px; height: 60px; font-size: 30px; }
    .eng-page-info h1 { font-size: 22px; }
    .eng-page-info p { font-size: 13px; }
    .banner-content { padding: 0 30px; }
    .banner-content h2 { font-size: 24px; }
    .banner-content p { font-size: 14px; }
    .compact-two-col { grid-template-columns: 1fr; }
    .product-grid { grid-template-columns: repeat(2, 1fr); }
    .footer-grid { grid-template-columns: 1fr; }
    .guarantee-bar { flex-wrap: wrap; gap: 15px; }
    .section-header h2 { font-size: 22px; }
    .filter-bar { flex-direction: column; align-items: flex-start; }
    .filter-form { width: 100%; }
    .detail-info-grid { grid-template-columns: 1fr; }
    .detail-actions { flex-direction: column; }
    .features-grid { grid-template-columns: 1fr; }
    .tech-grid { grid-template-columns: repeat(2, 1fr); }
    .hvac-features-grid { grid-template-columns: 1fr; }
    .pricing-grid { grid-template-columns: 1fr; }
    .contact-grid { grid-template-columns: 1fr; }
    .help-grid { grid-template-columns: 1fr; }
    .store-list-grid { grid-template-columns: 1fr; }
    .category-children { grid-template-columns: repeat(2, 1fr); }
    .flow-step { width: 100%; }
    .section-more { position: static; display: block; margin-top: 5px; }
    .stats-bar-inner { flex-wrap: wrap; gap: 4px; }

    .stats-grid { grid-template-columns: repeat(3, 1fr); }
    .eng-cate-split { flex-direction: column; gap: 20px; }
    .eng-cate-sidebar { width: 100%; }
    .eng-cate-sidebar-list { display: grid; grid-template-columns: repeat(3, 1fr); gap: 8px; }
    .eng-cate-product-grid { grid-template-columns: repeat(3, 1fr); }
    .platform-services-list { grid-template-columns: repeat(2, 1fr); }
    .stat-num { font-size: 28px; }
    .guarantee-grid { grid-template-columns: repeat(2, 1fr); }
    .article-grid { grid-template-columns: 1fr; }
    .merchant-grid { grid-template-columns: 1fr; }
    .eng-cate-topnav { flex-direction: column; align-items: flex-start; }
    .eng-cate-topnav-list { flex-wrap: wrap; }
    .eng-cate-topnav-item { flex: 1 1 calc(25% - 6px); min-width: 80px; }
    .eng-cate-oneline { flex-wrap: wrap; }
    .eng-cate-tag { flex: 1 1 calc(25% - 8px); min-width: 80px; }
    .hvac-modules-grid { grid-template-columns: 1fr; }
    .examples-grid { grid-template-columns: 1fr; }
    .ai-generate-form .form-row { grid-template-columns: 1fr; }
    .hvac-form-box { padding: 20px; }
    .form-hint { display: block; margin-left: 0; margin-top: 10px; }
    .register-modal { width: 95%; padding: 24px 20px; }
    .register-cate-grid { grid-template-columns: repeat(3, 1fr); }
}

@media (max-width: 480px) {
    .product-grid { grid-template-columns: 1fr; }
    .header-search form { flex-direction: column; gap: 5px; }
    .header-search input { border: 2px solid #1a5276; border-radius: 4px; }
    .header-search button { border-radius: 4px; }
    .banner-wrapper { height: 200px; }
    .banner-content h2 { font-size: 18px; }
    .banner-content p { font-size: 12px; }
    .banner-btn { padding: 6px 20px; font-size: 13px; }
    .logo-img { height: 36px; }
    .footer-beian { flex-direction: column; gap: 4px; }
    .beian-sep { display: none; }

    .pwa-modal { width: 95%; max-width: none; }
    .pwa-modal-body { font-size: 14px; }
    .pwa-guide-step { font-size: 13px; }

    .stats-grid { grid-template-columns: repeat(2, 1fr); }
    .eng-cate-sidebar-list { grid-template-columns: repeat(2, 1fr); }
    .eng-cate-product-grid { grid-template-columns: repeat(2, 1fr); }
    .eng-cate-oneline { justify-content: flex-start; }
    .eng-cate-tag { flex: 1 1 calc(50% - 8px); min-width: 70px; font-size: 13px; padding: 8px 4px; }
    .eng-cate-topnav-item { flex: 1 1 calc(50% - 6px); min-width: 70px; }
}

@media (max-width: 768px) {
    .ai-gen-form { padding: 16px; }
    .gen-select-row { flex-direction: column; align-items: stretch; }
    .gen-custom-input { width: 100%; }
    .gen-num-input { width: 100%; flex: 1; }
    .gen-output-row { flex-direction: column; }
    .gen-btn { padding: 10px 24px; font-size: 14px; }
    .ai-gen-hero h1 { font-size: 20px; }
}

@media (max-width: 480px) {
    .gen-export-row { flex-direction: column; align-items: stretch; }
    .gen-export-btn { width: 100%; }
    .gen-action-bar { flex-direction: column; }
    .gen-btn { width: 100%; }
}