/* ============================================================
   纸飞机 官网 - 独立样式表
   文件: css/style.css
   说明: 包含全局变量、布局、组件及响应式
   ============================================================ */

/* ---------- 全局变量 ---------- */
* {
            margin: 0;
            padding: 0;
            box-sizing: border-box;
        }

        body {
            font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
            background-color: #ffffff;
            color: #1e1e1e;
            line-height: 1.6;
            -webkit-font-smoothing: antialiased;
            scroll-behavior: smooth;
        }

        .container {
            max-width: 1200px;
            margin: 0 auto;
            padding: 0 24px;
        }

        /* ===== Telegram 蓝 (主色) ===== */
        :root {
            --telegram-blue: #0088cc;
            --telegram-blue-hover: #006699;
            --telegram-light-bg: #f5f9fc;
        }

        /* ===== 导航栏 ===== */
        .navbar {
            display: flex;
            align-items: center;
            justify-content: space-between;
            padding: 20px 0;
            border-bottom: 1px solid rgba(0, 136, 204, 0.08);
            flex-wrap: wrap;
            gap: 16px;
        }

        .nav-logo {
            display: flex;
            align-items: center;
            text-decoration: none;
        }

        .nav-logo img {
            height: 44px;
            width: auto;
            display: block;
        }

        .nav-links {
            display: flex;
            align-items: center;
            gap: 36px;
            list-style: none;
            flex-wrap: wrap;
        }

        .nav-links a {
            font-size: 16px;
            font-weight: 500;
            color: var(--telegram-blue);
            text-decoration: none;
            transition: color 0.2s, border-bottom 0.2s;
            padding-bottom: 4px;
            border-bottom: 2px solid transparent;
            cursor: pointer;
        }

        .nav-links a:hover {
            color: var(--telegram-blue-hover);
            border-bottom-color: var(--telegram-blue);
        }

        /* ===== 下载区域 (居中) ===== */
        .download-section {
            display: flex;
            flex-direction: column;
            align-items: center;
            text-align: center;
            padding: 60px 0 48px 0;
        }

        .download-logo {
            margin-bottom: 24px;
        }

        .download-logo img {
            height: 120px;
            width: auto;
            object-fit: contain;
        }

        .download-title {
            font-size: 42px;
            font-weight: 700;
            letter-spacing: -0.5px;
            color: #1e1e1e;
            margin-bottom: 12px;
        }

        .download-desc {
            font-size: 18px;
            color: #3a3a3a;
            max-width: 560px;
            margin: 0 auto 28px auto;
            line-height: 1.7;
        }

        .download-buttons {
            display: flex;
            flex-wrap: wrap;
            justify-content: center;
            gap: 16px 24px;
        }

        .download-btn {
            background-color: var(--telegram-blue);
            color: #fff;
            border: none;
            padding: 14px 36px;
            border-radius: 40px;
            font-size: 18px;
            font-weight: 600;
            cursor: pointer;
            transition: background 0.2s, transform 0.1s, box-shadow 0.2s;
            box-shadow: 0 4px 12px rgba(0, 136, 204, 0.25);
            display: inline-flex;
            align-items: center;
            gap: 14px;
            text-decoration: none;
            font-family: inherit;
        }

        .download-btn i {
            font-size: 20px;
        }

        .download-btn:hover {
            background-color: var(--telegram-blue-hover);
            transform: translateY(-2px);
            box-shadow: 0 8px 20px rgba(0, 136, 204, 0.35);
        }

        .download-btn:active {
            transform: scale(0.97);
        }

        .btn-outline {
            background: transparent;
            color: var(--telegram-blue);
            border: 2px solid var(--telegram-blue);
            padding: 12px 28px;
            border-radius: 40px;
            font-size: 16px;
            font-weight: 500;
            cursor: pointer;
            transition: all 0.2s;
            text-decoration: none;
            display: inline-flex;
            align-items: center;
            gap: 8px;
        }

        .btn-outline:hover {
            background: var(--telegram-blue);
            color: #fff;
        }

        .platform-icons {
            margin-top: 24px;
            display: flex;
            justify-content: center;
            gap: 28px;
            font-size: 28px;
            color: var(--telegram-blue);
            flex-wrap: wrap;
        }

        .platform-icons span {
            color: var(--telegram-blue);
            transition: color 0.2s, transform 0.2s;
            cursor: default;
        }

        .platform-icons span:hover {
            color: var(--telegram-blue-hover);
            transform: scale(1.05);
        }

        /* ===== 功能介绍区域 ===== */
        .features-section {
            padding: 60px 0 40px 0;
            border-top: 1px solid #f0f0f0;
        }

        .section-title {
            font-size: 32px;
            font-weight: 700;
            text-align: center;
            margin-bottom: 48px;
            letter-spacing: -0.3px;
        }
        .section-title i {
            color: var(--telegram-blue);
            margin-right: 8px;
        }

        .features-grid {
            display: grid;
            grid-template-columns: repeat(4, 1fr);
            gap: 32px 24px;
        }

        @media (max-width: 992px) {
            .features-grid {
                grid-template-columns: repeat(2, 1fr);
            }
        }

        @media (max-width: 540px) {
            .features-grid {
                grid-template-columns: 1fr;
            }
        }

        .feature-item {
            text-align: center;
            padding: 16px 8px;
            background: #fafcfe;
            border-radius: 24px;
            transition: box-shadow 0.2s;
            border: 1px solid transparent;
        }

        .feature-item:hover {
            box-shadow: 0 8px 24px rgba(0, 136, 204, 0.06);
            border-color: #e6f0f8;
        }

        .feature-item i {
            font-size: 38px;
            color: var(--telegram-blue);
            margin-bottom: 16px;
            display: inline-block;
        }

        .feature-item h3 {
            font-size: 20px;
            font-weight: 600;
            margin-bottom: 8px;
        }

        .feature-item p {
            font-size: 15px;
            color: #3d3d3d;
            line-height: 1.6;
        }

        /* ===== 版本介绍 ===== */
        .version-section {
            padding: 40px 0 32px 0;
            border-top: 1px solid #f0f0f0;
        }

        .version-grid {
            display: grid;
            grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
            gap: 24px;
            margin-top: 16px;
        }

        .version-card {
            background: #f8fafc;
            border-radius: 24px;
            padding: 24px 16px;
            text-align: center;
            transition: box-shadow 0.2s;
            border: 1px solid #eef2f6;
        }

        .version-card:hover {
            box-shadow: 0 8px 20px rgba(0,0,0,0.04);
        }

        .version-card i {
            font-size: 32px;
            color: var(--telegram-blue);
            margin-bottom: 10px;
        }
        .version-card h4 {
            font-size: 20px;
            font-weight: 600;
        }
        .version-card .badge {
            display: inline-block;
            background: var(--telegram-blue);
            color: #fff;
            font-size: 12px;
            padding: 2px 14px;
            border-radius: 30px;
            margin-top: 6px;
        }

        .download-center-wrapper {
            text-align: center;
            margin-top: 36px;
        }

        .btn-download-center {
            background: transparent;
            color: var(--telegram-blue);
            border: 2px solid var(--telegram-blue);
            padding: 12px 48px;
            border-radius: 40px;
            font-size: 18px;
            font-weight: 600;
            cursor: pointer;
            transition: all 0.25s;
            text-decoration: none;
            display: inline-flex;
            align-items: center;
            gap: 12px;
        }

        .btn-download-center:hover {
            background: var(--telegram-blue);
            color: #fff;
            box-shadow: 0 6px 16px rgba(0, 136, 204, 0.2);
        }

        /* ===== 安装 & 汉化步骤 ===== */
        .steps-section {
            padding: 48px 0 32px 0;
            border-top: 1px solid #f0f0f0;
        }

        .steps-wrapper {
            display: grid;
            grid-template-columns: 1fr 1fr;
            gap: 40px;
            margin-top: 16px;
        }

        @media (max-width: 700px) {
            .steps-wrapper {
                grid-template-columns: 1fr;
                gap: 32px;
            }
        }

        .step-block h3 {
            font-size: 22px;
            font-weight: 600;
            margin-bottom: 20px;
            color: #1e1e1e;
            display: flex;
            align-items: center;
            gap: 10px;
        }
        .step-block h3 i {
            color: var(--telegram-blue);
        }

        .step-list {
            list-style: none;
            counter-reset: step-counter;
        }

        .step-list li {
            counter-increment: step-counter;
            padding: 12px 0 12px 48px;
            position: relative;
            border-bottom: 1px solid #f2f2f2;
            font-size: 16px;
        }

        .step-list li::before {
            content: counter(step-counter);
            background: var(--telegram-blue);
            color: #fff;
            font-weight: 600;
            width: 28px;
            height: 28px;
            border-radius: 50%;
            display: flex;
            align-items: center;
            justify-content: center;
            position: absolute;
            left: 0;
            top: 10px;
            font-size: 14px;
        }

        .step-list li:last-child {
            border-bottom: none;
        }

        /* ===== 常见问题 FAQ ===== */
        .faq-section {
            padding: 48px 0 40px 0;
            border-top: 1px solid #f0f0f0;
        }

        .faq-grid {
            display: grid;
            grid-template-columns: repeat(2, 1fr);
            gap: 20px 32px;
            margin-top: 20px;
        }

        @media (max-width: 700px) {
            .faq-grid {
                grid-template-columns: 1fr;
            }
        }

        .faq-item {
            background: #f9fbfd;
            border-radius: 20px;
            padding: 20px 24px;
            border: 1px solid #edf2f7;
            transition: background 0.2s;
        }

        .faq-item:hover {
            background: #f2f7fc;
        }

        .faq-item h4 {
            font-size: 17px;
            font-weight: 600;
            color: #0b1a2a;
            display: flex;
            align-items: flex-start;
            gap: 10px;
            margin-bottom: 6px;
        }

        .faq-item h4 i {
            color: var(--telegram-blue);
            font-size: 18px;
            margin-top: 2px;
        }

        .faq-item p {
            font-size: 15px;
            color: #3d4a5a;
            margin-left: 32px;
        }

        /* ===== 页脚 ===== */
        .footer {
            border-top: 1px solid #eaeef2;
            padding: 40px 0 32px 0;
            margin-top: 20px;
            background: #fafcfe;
        }

        .footer-content {
            display: flex;
            flex-wrap: wrap;
            justify-content: space-between;
            align-items: center;
            gap: 20px;
        }

        .footer-copy {
            font-size: 14px;
            color: #5d6b7a;
        }

        .footer-social a {
            color: var(--telegram-blue);
            margin-left: 20px;
            font-size: 20px;
            transition: color 0.2s;
            text-decoration: none;
        }

        .footer-social a:hover {
            color: var(--telegram-blue-hover);
        }

        .footer-links a {
            color: #3d4a5a;
            text-decoration: none;
            margin: 0 12px;
            font-size: 14px;
        }

        .footer-links a:hover {
            color: var(--telegram-blue);
        }

        .text-center { text-align: center; }
        .mt-8 { margin-top: 8px; }
        .mb-8 { margin-bottom: 8px; }
        
        /* 友情链接模块样式 */
.links-section {
    padding: 40px 0;
    margin-top: 30px;
}

.links-grid {
    display: flex;
    flex-wrap: wrap;
    gap: 15px;
    justify-content: center;
    margin-top: 20px;
}

.link-item {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    padding: 10px 18px;
    background-color: #ffffff;
    border: 1px solid #e2e8f0;
    border-radius: 8px;
    color: #334155;
    text-decoration: none;
    font-size: 14px;
    transition: all 0.3s ease;
}

.link-item:hover {
    color: #0088cc;
    border-color: #0088cc;
    transform: translateY(-2px);
    box-shadow: 0 4px 12px rgba(0, 136, 204, 0.15);
}