:root {
        --signal-blue-light: #e6e9f5;
        --signal-blue-dark: #3a5497;
        --signal-hero-bg: #9DBBF8;
        --signal-footer-bg: #333333;
        --signal-text-dark: #333;
    }

    .navbar-brand { font-weight: 700; color: var(--signal-text-dark) !important; }
    .navbar-brand img { height: 43px; width: auto; }
    .navbar-toggler {
        border: none !important; 
        box-shadow: none !important; 
    }
    
    .hero-section {
        background-color: var(--signal-hero-bg);
        color: black;
        padding: 80px 0 0 0; 
        overflow: visible; 
        position: relative;
        padding-bottom: 200px; 
    }
    .hero-content { z-index: 10; padding-bottom: 50px; }

    .hero-image-placeholder {
        position: absolute;
        bottom: -200px; 
        right: 0%; 
        width: 650px; 
        height: 700px; 
        z-index: 5;
        transform: rotate(25deg); 
    }
    
    .hero-image-placeholder .phone-video {
        position: absolute;
        bottom: 0px; 
        left: -5%; 
        max-width: 280px; 
        height: auto;
        transform: none; 
        z-index: 7;
    }

    .hero-image-placeholder .phone-chat {
        position: absolute;
        bottom: 180px; 
        left: 27%; 
        max-width: 280px;
        height: auto;
        transform: none; 
        z-index: 8; 
    }

    .hero-section .btn {
        background-color: white !important;
        color: #2C6BED !important; 
        border: none !important;
    }

    .section-padding { padding: 80px 0; }
    .section-heading-small {
        font-size: 1.1rem;
        color: #777; 
        margin-bottom: 40px;
    }
    
    .why-signal-img-box {
        border-radius: 12px;
        padding: 40px;
    }
    
    .feature-card {
        border: 1px solid #ddd;
        border-radius: 12px;
        padding: 40px 20px; 
        box-shadow: 0 4px 10px rgba(0, 0, 0, 0.05);
        min-height: 320px; 
        text-align: center; 
        display: flex;
        flex-direction: column;
        align-items: center;
        justify-content: center;
    }
    .feature-card h4 {
         font-size: 1.25rem;
         margin-top: 15px;
         margin-bottom: 10px;
         font-weight: bold;
    }
    .feature-icon-wrapper {
         margin-bottom: 20px;
    }
    .feature-card img {
        float: none;
        max-height: 450px; 
        width: auto;
        margin-right: 0;
        margin-bottom: 0;
    }
    .card-content-wrapper p {
         font-size: 1.3rem;
         color: #555;
         
    }
    .illus-chat { padding: 15px; border-radius: 8px; }
    .illus-video {  padding: 15px; border-radius: 8px; }
    .illus-sticker {  padding: 15px; border-radius: 8px; }
    .illus-group { padding: 15px; border-radius: 8px; }
    
    .no-ads-section { background-color: var(--signal-blue-light); }
    .illustration-box {
        border-radius: 12px;
        padding: 40px;
        min-height: 250px;
        display: flex;
        align-items: center;
        justify-content: center;
    }
    
    .free-cta-btn {
        background-color: #2C6BED;
        border-color: #2C6BED;
    }

    .footer-section {
        background-color: var(--signal-footer-bg);
        color: #ccc;
        padding: 40px 0;
        font-size: 0.85rem;
        text-align: center; 
    }
    .footer-section a { color: #fff; }

    @media (max-width: 991px) {
        .hero-section { 
            padding-bottom: 50px; 
            overflow: hidden; 
        }

        .hero-image-placeholder { 
            position: static; 
            width: 100%; 
            height: auto; 
            margin-top: 30px; 
            display: flex !important; 
            justify-content: center;
            align-items: center;
            flex-direction: row;
            transform: none; 
            bottom: auto; 
        }
        
        .hero-image-placeholder .phone-video,
        .hero-image-placeholder .phone-chat { 
            position: static;
            max-width: 45%; 
            height: auto;
            border-radius: 20px;
            transform: none !important; 
            margin: 0 5px;
            z-index: auto;
        }
        
        .hero-content { padding-bottom: 30px; }
        .section-padding { padding: 40px 0; }
            
    }

    .why-signal-top-spacing {
        margin-top: 80px; 
    }
    
    @media (min-width: 992px) {
        .why-signal-top-spacing {
            margin-top: 140px; 
        }
    }

    /* ========== 多平台下载板块 ========== */
    .download-section {
        background: linear-gradient(180deg, #f0f4ff 0%, #ffffff 100%);
        padding: 60px 0;
    }
    .download-card {
        border-radius: 16px;
        transition: transform 0.3s ease, box-shadow 0.3s ease;
    }
    .download-card:hover {
        transform: translateY(-6px);
        box-shadow: 0 14px 40px rgba(0,0,0,0.12) !important;
    }
    .download-card .btn-primary {
        background-color: #4A4AFF;
        border-color: #4A4AFF;
        border-radius: 8px;
        padding: 10px 0;
        font-weight: 600;
    }
    .download-card .btn-outline-secondary {
        border-radius: 8px;
        padding: 10px 0;
    }

    /* ========== 竞品对比表格 ========== */
    .comparison-section {
        background-color: #f8f9fc;
    }
    .comparison-table {
        font-size: 0.95rem;
        border-collapse: separate;
        border-spacing: 0;
        border-radius: 12px;
        overflow: hidden;
        box-shadow: 0 2px 20px rgba(0,0,0,0.08);
    }
    .comparison-table thead th {
        border-bottom: 2px solid #dee2e6;
        font-size: 1.05rem;
        padding: 16px 12px;
        vertical-align: middle;
    }
    .comparison-table .signal-col {
        background-color: #e8f0fe;
        color: #1a56db;
    }
    .comparison-table tbody td {
        padding: 14px 12px;
        vertical-align: middle;
        border-color: #e9ecef;
    }
    .comparison-table tbody tr:hover {
        background-color: #f1f5fd;
        transition: background-color 0.2s ease;
    }
    .comparison-table tbody td:first-child {
        font-weight: 600;
        background-color: #fafbff;
    }

    /* ========== 名人背书 (E-E-A-T) ========== */
    .endorsements-section {
        background-color: #f0f2f5;
    }
    .endorsement-card {
        border-radius: 16px;
        transition: transform 0.3s ease, box-shadow 0.3s ease;
    }
    .endorsement-card:hover {
        transform: translateY(-6px);
        box-shadow: 0 12px 40px rgba(0,0,0,0.12) !important;
    }
    .endorsement-card .blockquote p {
        font-style: italic;
        color: #333;
        font-size: 0.95rem;
        line-height: 1.7;
    }
    .endorsement-card .blockquote p::before {
        content: open-quote;
        font-size: 2rem;
        color: #4A4AFF;
        line-height: 0;
        vertical-align: -0.4em;
    }
    .endorsement-card .blockquote p::after {
        content: close-quote;
        font-size: 2rem;
        color: #4A4AFF;
        line-height: 0;
        vertical-align: -0.4em;
    }

    /* ========== FAQ (People Also Ask) ========== */
    .faq-section {
        background-color: #ffffff;
    }
    .faq-section .accordion-button {
        font-size: 1.05rem;
        color: #1a1a1a;
        background-color: #f8f9fa;
        border-radius: 8px !important;
        padding: 18px 24px;
    }
    .faq-section .accordion-button:not(.collapsed) {
        background-color: #e8f0fe;
        color: #1a56db;
        font-weight: 700;
    }
    .faq-section .accordion-button:focus {
        box-shadow: 0 0 0 3px rgba(74,74,255,0.25);
        border-color: #4A4AFF;
    }
    .faq-section .accordion-body {
        padding: 20px 24px;
        font-size: 0.98rem;
        line-height: 1.8;
        color: #444;
        background-color: #fdfdfd;
    }
    .faq-section .accordion-item {
        border: 1px solid #e0e0e0 !important;
    }
    .disclaimer-box a:hover {
        color: #ffc107 !important;
        text-decoration: underline !important;
    }

    /* ========== 多列 Footer ========== */
    .footer-section {
        background-color: var(--signal-footer-bg);
        color: #ccc;
        padding: 50px 0 40px;
        font-size: 0.88rem;
    }
    .footer-section a { color: #ccc; transition: color 0.2s ease; }
    .footer-section a:hover { color: #fff !important; }
    .footer-brand-col p { line-height: 1.7; }
    .footer-links li {
        margin-bottom: 8px;
        list-style-type: none;
        position: relative;
        padding-left: 0;
    }
    .footer-links a {
        display: inline-block;
        text-decoration: none;
        color: #bbb;
        font-size: 0.9rem;
    }
    .footer-links a:hover {
        color: #fff;
        text-decoration: none;
    }

    @media (max-width: 767px) {
        .comparison-table {
            font-size: 0.8rem;
        }
        .comparison-table thead th,
        .comparison-table tbody td {
            padding: 10px 6px;
        }
        .endorsement-card {
            margin-bottom: 16px;
        }
    }