:root {
    --primary: #2563eb;
    --primary-dark: #1d4ed8;
    --bg: #ffffff;
    --bg-secondary: #f8fafc;
    --text: #1e293b;
    --text-muted: #64748b;
    --border: #e2e8f0;
    --card-shadow: 0 1px 3px rgba(0,0,0,.08);
    --header-height: 64px;
}

[data-theme="dark"] {
    --primary: #3b82f6;
    --primary-dark: #2563eb;
    --bg: #0f172a;
    --bg-secondary: #1e293b;
    --text: #f1f5f9;
    --text-muted: #94a3b8;
    --border: #334155;
    --card-shadow: 0 1px 3px rgba(0,0,0,.4);
}

* { box-sizing: border-box; }
body { font-family: 'Nunito', 'Segoe UI', system-ui, -apple-system, sans-serif; color: var(--text); background: var(--bg); line-height: 1.6; }
a { color: var(--primary); text-decoration: none; }
a:hover { color: var(--primary-dark); }

/* Inner pages header — Omni style */
.page-inner {
    font-family: 'Nunito', 'Segoe UI', system-ui, sans-serif;
    background: #f5f7fa;
}

.omni-inner-header {
    background: #fff;
    border-bottom: 1px solid #eef1f5;
    z-index: 1030;
}

.omni-header-top {
    display: grid;
    grid-template-columns: auto 1fr auto;
    align-items: center;
    gap: 1.5rem;
    padding: 0.85rem 0;
    position: relative;
}

.omni-inner-logo {
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    text-decoration: none !important;
    flex-shrink: 0;
}

.omni-inner-logo-mark {
    width: 28px;
    height: 28px;
    border-radius: 50%;
    background: conic-gradient(from 180deg, #ff6b4a, #f5c518, #3498db, #9b59b6, #ff6b4a);
    flex-shrink: 0;
}

.omni-inner-logo-text {
    font-size: 1.35rem;
    line-height: 1;
    white-space: nowrap;
}

.omni-inner-logo-bold {
    font-weight: 800;
    color: #1e3a5f;
}

.omni-inner-logo-light {
    font-weight: 600;
    color: #288dfd;
}

.omni-header-search {
    position: relative;
    max-width: 640px;
    width: 100%;
    margin: 0 auto;
}

.omni-header-search-input {
    width: 100%;
    height: 46px;
    padding: 0 3rem 0 1.25rem;
    border: none;
    border-radius: 50px;
    background: #f0f3f7;
    font-family: inherit;
    font-size: 0.95rem;
    font-weight: 600;
    color: #2d3a4a;
    outline: none;
    transition: background 0.2s, box-shadow 0.2s;
}

.omni-header-search-input::placeholder {
    color: #8a96a8;
}

.omni-header-search-input:focus {
    background: #fff;
    box-shadow: inset 0 0 0 2px #288dfd;
}

.omni-header-search-btn {
    position: absolute;
    right: 6px;
    top: 50%;
    transform: translateY(-50%);
    width: 36px;
    height: 36px;
    border: none;
    background: transparent;
    color: #288dfd;
    font-size: 1rem;
    cursor: pointer;
    border-radius: 50%;
}

.omni-header-actions {
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.omni-header-icon-btn {
    width: 40px;
    height: 40px;
    border-radius: 50%;
    border: none;
    background: #f0f3f7;
    color: #5a6a7e;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: background 0.15s;
}

.omni-header-icon-btn:hover {
    background: #e8ecf1;
}

.omni-mobile-toggle {
    display: none;
    position: absolute;
    right: 0;
    top: 50%;
    transform: translateY(-50%);
    border: none;
    background: transparent;
    font-size: 1.25rem;
    color: #2d3a4a;
    padding: 0.5rem;
}

/* Category navigation strip */
.omni-cat-nav {
    border-top: 1px solid #f0f3f7;
    background: #fff;
}

.omni-cat-nav-list {
    display: flex;
    align-items: center;
    gap: 0;
    list-style: none;
    margin: 0;
    padding: 0;
    overflow-x: auto;
    scrollbar-width: none;
    -ms-overflow-style: none;
}

.omni-cat-nav-list::-webkit-scrollbar {
    display: none;
}

.omni-cat-nav-list li {
    flex-shrink: 0;
}

.omni-cat-nav-link {
    display: block;
    padding: 0.85rem 1.1rem;
    font-size: 0.95rem;
    font-weight: 700;
    color: #3d4f63 !important;
    text-decoration: none !important;
    white-space: nowrap;
    border-bottom: 3px solid transparent;
    transition: color 0.15s, border-color 0.15s;
}

.omni-cat-nav-link:hover {
    color: #288dfd !important;
}

.omni-cat-nav-link.is-active {
    color: #288dfd !important;
    border-bottom-color: #288dfd;
}

@media (max-width: 991.98px) {
    .omni-header-top {
        grid-template-columns: 1fr auto;
        gap: 0.75rem;
        padding-right: 2.5rem;
    }

    .omni-header-search {
        grid-column: 1 / -1;
        order: 3;
        max-width: 100%;
    }

    .omni-header-actions {
        order: 2;
    }

    .omni-inner-logo {
        order: 1;
    }

    .omni-mobile-toggle {
        display: block;
    }

    .omni-cat-nav.collapse:not(.show) {
        display: none;
    }

    .omni-cat-nav-list {
        flex-direction: column;
        align-items: stretch;
        padding: 0.5rem 0 1rem;
    }

    .omni-cat-nav-link {
        border-bottom: none;
        border-left: 3px solid transparent;
        padding: 0.65rem 0.5rem;
    }

    .omni-cat-nav-link.is-active {
        border-left-color: #288dfd;
        background: #f0f6ff;
    }
}

/* Legacy header (unused) */
.site-header { background: var(--bg); border-bottom: 1px solid var(--border); z-index: 1030; }

/* Omni search dropdown (global — header + hero) */
.omni-search-wrap { position: relative; z-index: 100; }

.omni-search-dropdown {
    display: none;
    position: absolute;
    top: calc(100% + 6px);
    left: 0;
    right: 0;
    background: #fff;
    border: 1px solid #e8ecf1;
    border-radius: 14px;
    box-shadow: 0 12px 40px rgba(0, 0, 0, 0.12);
    z-index: 9999;
    max-height: 380px;
    overflow-y: auto;
    padding: 0.35rem 0;
}

.omni-search-dropdown.is-open { display: block; }

.omni-search-item {
    display: flex;
    align-items: center;
    gap: 0.45rem;
    padding: 0.85rem 1.25rem;
    color: #2d3a4a !important;
    text-decoration: none !important;
    font-size: 1rem;
    font-weight: 600;
    transition: background 0.12s;
}

.omni-search-item:hover,
.omni-search-item.is-highlighted { background: #f0f6ff; }

.omni-search-item-title { color: #2d3a4a; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
.omni-search-item-dot { color: #e74c3c; font-size: 1.1rem; flex-shrink: 0; }
.omni-search-item-cat { color: #8a96a8; font-weight: 600; flex-shrink: 0; }
.omni-search-empty { padding: 1rem 1.25rem; color: #8a96a8; font-weight: 600; }

.mega-menu { min-width: 700px; border: none; box-shadow: 0 12px 40px rgba(0,0,0,.15); border-radius: 12px; }
.mega-cat-link { display: block; font-weight: 600; margin-bottom: .5rem; color: var(--text); }
.mega-sub-link { display: block; font-size: .85rem; color: var(--text-muted); padding: .15rem 0; }

/* Hero */
.hero-section { background: linear-gradient(135deg, #1e40af 0%, #2563eb 50%, #3b82f6 100%); color: #fff; padding: 4rem 0; }
.hero-content h1 { font-size: 2.75rem; font-weight: 800; margin-bottom: 1rem; }
.hero-search { max-width: 600px; margin-top: 2rem; }
.hero-search .form-control { border: none; }
.hero-search .btn { background: #f59e0b; border-color: #f59e0b; }

/* Sections */
.section-title { font-weight: 700; margin-bottom: 1.5rem; font-size: 1.5rem; }
.bg-light { background: var(--bg-secondary) !important; }

/* Category cards */
.category-card { display: block; background: var(--bg); border: 1px solid var(--border); border-radius: 12px; padding: 1.5rem; text-align: center; transition: all .2s; color: var(--text); height: 100%; }
.category-card:hover { transform: translateY(-4px); box-shadow: 0 8px 24px rgba(0,0,0,.1); border-color: var(--primary); }
.cat-icon { width: 56px; height: 56px; border-radius: 12px; display: flex; align-items: center; justify-content: center; margin: 0 auto 1rem; font-size: 1.5rem; }
.category-card h3 { font-size: 1rem; font-weight: 600; margin-bottom: .25rem; }
.cat-count { font-size: .8rem; color: var(--text-muted); }

/* Calculator cards */
.calc-card { display: block; background: var(--bg); border: 1px solid var(--border); border-radius: 14px; padding: 1.35rem 1.25rem; transition: all .22s ease; color: var(--text); height: 100%; text-decoration: none !important; position: relative; overflow: hidden; }
.calc-card::before { content: ''; position: absolute; top: 0; left: 0; right: 0; height: 3px; background: linear-gradient(90deg, #288dfd, #3b82f6); opacity: 0; transition: opacity .22s; }
.calc-card:hover { transform: translateY(-4px); box-shadow: 0 12px 32px rgba(40, 141, 253, 0.12); border-color: #93c5fd; }
.calc-card:hover::before { opacity: 1; }
.calc-card-icon {
    width: 44px;
    height: 44px;
    border-radius: 12px;
    display: flex;
    align-items: center;
    justify-content: center;
    margin-bottom: .75rem;
    font-size: 1.15rem;
    box-shadow: 0 3px 10px rgba(0, 0, 0, 0.1);
    transition: transform 0.2s;
}
.calc-card:hover .calc-card-icon { transform: scale(1.06); }
.calc-card-icon i { font-weight: 900; }
.calc-card-title { font-size: 1rem; font-weight: 700; margin-bottom: .5rem; line-height: 1.35; color: #1e293b; }
.calc-card-desc { font-size: .82rem; color: var(--text-muted); margin-bottom: .85rem; line-height: 1.5; display: -webkit-box; -webkit-line-clamp: 2; -webkit-box-orient: vertical; overflow: hidden; }
.calc-card-meta { display: flex; justify-content: space-between; align-items: center; font-size: .75rem; gap: 0.5rem; padding-top: 0.65rem; border-top: 1px solid #f1f5f9; }
.calc-card-meta .views { color: var(--text-muted); }

/* Category page */
.category-banner { padding: 2rem 0; }
.category-header { display: flex; align-items: center; gap: 1.5rem; }
.category-header h1 {
    font-size: clamp(1.5rem, 3vw, 2rem);
    font-weight: 800;
    margin-bottom: 0.35rem;
    color: #1e3a5f;
}
.category-header p {
    margin: 0;
    color: #5a6a7e;
    font-size: 0.95rem;
    max-width: 640px;
}

.category-listing {
    padding: 1.75rem 0 3rem;
    font-family: 'Nunito', 'Segoe UI', system-ui, sans-serif;
}

.category-content-section {
    padding: 0 0 3rem;
    background: #f8fafc;
    border-top: 1px solid #e8ecf1;
}

.category-content-section .category-article {
    margin-top: 0;
}

.cat-toolbar {
    background: #fff;
    border: 1px solid #e8ecf1;
    border-radius: 16px;
    padding: 1.1rem 1.25rem;
    margin-bottom: 1.75rem;
    box-shadow: 0 4px 20px rgba(30, 58, 95, 0.06);
    overflow: visible;
}

.cat-toolbar-row {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 1rem 1.5rem;
    flex-wrap: wrap;
}

.cat-search-form {
    flex: 1 1 320px;
    min-width: 0;
    max-width: 520px;
}

.cat-search-wrap {
    position: relative;
    display: flex;
    align-items: center;
    gap: 0.5rem;
    background: #f5f7fa;
    border: 1px solid #e2e8f0;
    border-radius: 12px;
    padding: 0.35rem 0.4rem 0.35rem 0.9rem;
    transition: border-color 0.2s, box-shadow 0.2s, background 0.2s;
    z-index: 20;
}

.cat-search-wrap .omni-search-dropdown {
    top: calc(100% + 8px);
    border-radius: 12px;
}

.cat-search-wrap:focus-within {
    background: #fff;
    border-color: #288dfd;
    box-shadow: 0 0 0 3px rgba(40, 141, 253, 0.15);
}

.cat-search-icon {
    color: #8a96a8;
    font-size: 0.9rem;
    flex-shrink: 0;
}

.cat-search-input {
    flex: 1;
    min-width: 0;
    border: none;
    background: transparent;
    font-size: 0.95rem;
    font-weight: 600;
    color: #1e3a5f;
    padding: 0.45rem 0;
    outline: none;
}

.cat-search-input::placeholder {
    color: #a0aec0;
    font-weight: 500;
}

.cat-search-clear {
    display: flex;
    align-items: center;
    justify-content: center;
    width: 28px;
    height: 28px;
    border-radius: 8px;
    color: #8a96a8;
    text-decoration: none;
    flex-shrink: 0;
    transition: background 0.15s, color 0.15s;
}

.cat-search-clear:hover {
    background: #e8ecf1;
    color: #1e3a5f;
}

.cat-search-btn {
    display: inline-flex;
    align-items: center;
    gap: 0.4rem;
    border: none;
    border-radius: 9px;
    padding: 0.55rem 1rem;
    background: linear-gradient(135deg, #288dfd 0%, #1a6fd4 100%);
    color: #fff;
    font-size: 0.85rem;
    font-weight: 800;
    white-space: nowrap;
    cursor: pointer;
    transition: transform 0.15s, box-shadow 0.15s;
    box-shadow: 0 2px 8px rgba(40, 141, 253, 0.35);
}

.cat-search-btn:hover {
    transform: translateY(-1px);
    box-shadow: 0 4px 12px rgba(40, 141, 253, 0.4);
}

.cat-result-badge {
    display: inline-flex;
    align-items: baseline;
    gap: 0.35rem;
    padding: 0.55rem 1rem;
    background: linear-gradient(135deg, #f0f7ff 0%, #e8f4fd 100%);
    border: 1px solid #d4e8fc;
    border-radius: 12px;
    flex-shrink: 0;
}

.cat-result-num {
    font-size: 1.35rem;
    font-weight: 800;
    color: #288dfd;
    line-height: 1;
}

.cat-result-label {
    font-size: 0.85rem;
    font-weight: 700;
    color: #5a6a7e;
}

.cat-subnav {
    display: flex;
    align-items: flex-start;
    gap: 0.85rem;
    margin-top: 1rem;
    padding-top: 1rem;
    border-top: 1px solid #eef2f6;
    flex-wrap: wrap;
}

.cat-subnav-label {
    display: inline-flex;
    align-items: center;
    gap: 0.4rem;
    font-size: 0.78rem;
    font-weight: 800;
    text-transform: uppercase;
    letter-spacing: 0.04em;
    color: #8a96a8;
    padding-top: 0.45rem;
    flex-shrink: 0;
}

.cat-subnav-label i {
    font-size: 0.72rem;
    opacity: 0.85;
}

.cat-subnav-pills {
    display: flex;
    flex-wrap: wrap;
    gap: 0.5rem;
    flex: 1;
}

.cat-sub-pill {
    display: inline-flex;
    align-items: center;
    gap: 0.45rem;
    padding: 0.4rem 0.85rem 0.4rem 0.45rem;
    background: #f8fafc;
    border: 1px solid #e8ecf1;
    border-radius: 999px;
    color: #1e3a5f;
    font-size: 0.85rem;
    font-weight: 700;
    text-decoration: none;
    transition: all 0.2s;
}

.cat-sub-pill:hover {
    background: #fff;
    border-color: #288dfd;
    color: #288dfd;
    transform: translateY(-1px);
    box-shadow: 0 4px 12px rgba(40, 141, 253, 0.12);
}

.cat-sub-pill-icon {
    width: 26px;
    height: 26px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 0.7rem;
    flex-shrink: 0;
}

.cat-search-hint {
    margin: -0.75rem 0 1.25rem;
    font-size: 0.9rem;
    color: #5a6a7e;
    font-weight: 600;
}

.cat-search-hint a {
    margin-left: 0.5rem;
    color: #288dfd;
    font-weight: 700;
    text-decoration: none;
}

.cat-search-hint a:hover {
    text-decoration: underline;
}

.cat-grid {
    margin-top: 0.25rem;
}

.cat-collection-section {
    margin-bottom: 2.5rem;
}

.cat-collection-title {
    font-size: 1.25rem;
    font-weight: 800;
    color: #1e3a5f;
    margin: 0 0 1.25rem;
    display: flex;
    align-items: center;
    gap: 0.55rem;
    padding-bottom: 0.65rem;
    border-bottom: 2px solid #eef2f6;
}

.cat-collection-title i {
    color: #f97316;
    font-size: 1.1rem;
}

.page-inner .category-banner[style*="construction"] .cat-collection-title i,
.category-listing .cat-collection-title i {
    color: #f59e0b;
}

.cat-pagination {
    margin-top: 2.5rem;
}

.cat-pagination .page-link {
    border-radius: 8px;
    margin: 0 2px;
    font-weight: 700;
    color: #5a6a7e;
    border-color: #e8ecf1;
}

.cat-pagination .page-item.active .page-link {
    background: #288dfd;
    border-color: #288dfd;
}

@media (max-width: 767.98px) {
    .cat-toolbar-row {
        flex-direction: column;
        align-items: stretch;
    }

    .cat-search-form {
        max-width: none;
    }

    .cat-result-badge {
        justify-content: center;
    }

    .cat-subnav {
        flex-direction: column;
        gap: 0.65rem;
    }

    .cat-subnav-label {
        padding-top: 0;
    }

    .cat-search-btn span {
        display: none;
    }

    .cat-search-btn {
        padding: 0.55rem 0.75rem;
    }
}
.cat-banner-icon-wrap,
.omni-cat-icon {
    width: 56px;
    height: 56px;
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: 14px;
    box-shadow: 0 4px 14px rgba(0, 0, 0, 0.12);
    font-size: 1.45rem;
}
.cat-banner-icon-wrap { width: 72px; height: 72px; font-size: 1.75rem; margin-bottom: 0; flex-shrink: 0; }
.omni-cat-icon i,
.cat-banner-icon-wrap i { font-weight: 900; }

/* Calculator page */
.calc-panel { background: var(--bg); border: 1px solid var(--border); border-radius: 16px; padding: 2rem; }
.calc-title { font-size: 1.75rem; font-weight: 700; }
.calc-subtitle { color: var(--text-muted); margin-bottom: 1.5rem; }
.unit-label { font-weight: 400; color: var(--text-muted); font-size: .85rem; }
.calc-actions { display: flex; flex-wrap: wrap; gap: .5rem; margin-top: 1rem; padding-top: 1rem; border-top: 1px solid var(--border); }

.results-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(200px, 1fr)); gap: 1rem; }
.result-card { background: linear-gradient(135deg, var(--primary), var(--primary-dark)); color: #fff; border-radius: 12px; padding: 1.25rem; }
.result-label { font-size: .8rem; opacity: .9; margin-bottom: .25rem; }
.result-value { font-size: 1.5rem; font-weight: 700; }

.formula-box { background: var(--bg-secondary); border-left: 4px solid var(--primary); padding: 1rem 1.5rem; border-radius: 0 8px 8px 0; margin: 1rem 0; }
.calc-article h2 { margin-top: 2rem; font-size: 1.35rem; font-weight: 700; }

.sidebar-card { background: var(--bg); border: 1px solid var(--border); border-radius: 12px; padding: 1.25rem; margin-bottom: 1rem; }
.sidebar-card h4 { font-size: 1rem; font-weight: 600; margin-bottom: 1rem; }
.related-list { list-style: none; padding: 0; margin: 0; }
.related-list li { padding: .5rem 0; border-bottom: 1px solid var(--border); }
.related-list li:last-child { border-bottom: none; }
.related-list a { color: var(--text); font-size: .9rem; }
.related-list i { color: var(--primary); margin-right: .5rem; }

/* Footer v2 */
.footer-v2 {
    font-family: 'Nunito', 'Segoe UI', system-ui, sans-serif;
    margin-top: 0;
    background: #fff;
}

.footer-main {
    background: #fff;
    border-top: 1px solid #e8ecf1;
    padding: 3.5rem 0 2.5rem;
}

.footer-brand {
    max-width: 320px;
}

.footer-logo-link {
    display: inline-block;
    margin-bottom: 1rem;
}

.footer-logo {
    height: 44px;
    width: auto;
    max-width: 100%;
    object-fit: contain;
}

.footer-tagline {
    font-size: 1.35rem;
    font-weight: 800;
    color: #1e3a5f;
    margin: 0 0 0.75rem;
    line-height: 1.3;
}

.footer-desc {
    font-size: 0.9rem;
    font-weight: 600;
    color: #8a96a8;
    line-height: 1.65;
    margin-bottom: 1.5rem;
}

.footer-social {
    display: flex;
    gap: 0.6rem;
    flex-wrap: wrap;
}

.footer-social a {
    display: flex;
    align-items: center;
    justify-content: center;
    width: 38px;
    height: 38px;
    border-radius: 10px;
    background: #fff;
    border: 1px solid #e8ecf1;
    color: #5a6a7e !important;
    font-size: 0.9rem;
    text-decoration: none;
    transition: all 0.2s;
    box-shadow: 0 1px 4px rgba(0, 0, 0, 0.04);
}

.footer-social a:hover {
    background: #288dfd;
    border-color: #288dfd;
    color: #fff !important;
    transform: translateY(-2px);
}

.footer-heading {
    font-size: 0.8rem;
    font-weight: 800;
    text-transform: uppercase;
    letter-spacing: 0.06em;
    color: #1e3a5f;
    margin-bottom: 1.25rem;
}

.footer-cat-grid {
    list-style: none;
    padding: 0;
    margin: 0;
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 0.5rem 1rem;
}

.footer-cat-grid a {
    display: flex;
    align-items: center;
    gap: 0.55rem;
    color: #3d4f63 !important;
    text-decoration: none !important;
    font-size: 0.88rem;
    font-weight: 700;
    padding: 0.35rem 0;
    transition: color 0.15s;
}

.footer-cat-grid a:hover {
    color: #288dfd !important;
}

.footer-cat-icon {
    width: 28px;
    height: 28px;
    border-radius: 8px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 0.75rem;
    flex-shrink: 0;
}

.footer-links {
    list-style: none;
    padding: 0;
    margin: 0;
}

.footer-links li {
    margin-bottom: 0.65rem;
}

.footer-links a {
    color: #5a6a7e !important;
    text-decoration: none !important;
    font-size: 0.9rem;
    font-weight: 700;
    transition: color 0.15s;
}

.footer-links a:hover {
    color: #288dfd !important;
}

.footer-bottom {
    background: #fff;
    border-top: 1px solid #e8ecf1;
    padding: 1.15rem 0;
}

.footer-bottom-inner {
    display: flex;
    align-items: center;
    justify-content: center;
    text-align: center;
}

.footer-copyright {
    margin: 0;
    font-size: 0.85rem;
    font-weight: 600;
    color: #8a96a8;
}

@media (max-width: 767.98px) {
    .footer-main {
        padding: 2.5rem 0 2rem;
    }

    .footer-cat-grid {
        grid-template-columns: 1fr;
    }
}

/* Responsive */
@media (max-width: 768px) {
    .hero-content h1 { font-size: 1.75rem; }
    .mega-menu { min-width: auto; }
    .calc-panel { padding: 1.25rem; }
    .results-grid { grid-template-columns: 1fr; }
}



.calc-ref-table {
    width: 100%;
    border-collapse: collapse;
    margin: 20px 0;
    font-size: 16px;
    background: #fff;
}

.calc-ref-table th,
.calc-ref-table td {
    border: 1px solid #ddd;
    padding: 12px 15px;
    text-align: left;
    vertical-align: middle;
}

.calc-ref-table th {
    background: #f5f5f5;
    font-weight: 600;
}

.calc-ref-table tbody tr:nth-child(even) {
    background: #fafafa;
}

.calc-ref-table tbody tr:hover {
    background: #f1f1f1;
    transition: background 0.3s ease;
}