:root {
            --primary: #1b4d3e;
            --primary-hover: #143d31;
            --accent: #f39c12;
            --bg: #f4f7f6;
            --card-bg: #ffffff;
            --text-dark: #1e293b;
            --text-muted: #64748b;
            --border: #e2e8f0;
            --radius: 16px;
        }

        * {
            box-sizing: border-box;
            margin: 0;
            padding: 0;
            font-family: system-ui, -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
        }

        body {
            background-color: var(--bg);
            color: var(--text-dark);
            line-height: 1.8;
        }

         /* Header & Navigation */
        header {
            background-color: var(--primary);
            color: #ffffff;
            box-shadow: 0 4px 20px rgba(0,0,0,0.08);
            position: sticky;
            top: 0;
            z-index: 100;
        }

        .header-container {
            max-width: 1100px;
            margin: 0 auto;
            padding: 14px 20px;
            display: flex;
            justify-content: space-between;
            align-items: center;
        }

      .logo {
            font-size: 1.3rem;
            font-weight: 700;
            color: #ffffff;
            text-decoration: none;
            display: flex;
            align-items: center;
            gap: 8px;
        }


        .nav-links {
            display: flex;
            gap: 20px;
        }

        .nav-links a {
            color: #e2e8f0;
            text-decoration: none;
            font-size: 0.95rem;
            transition: color 0.2s;
        }

        .nav-links a:hover {
            color: var(--accent);
        }

        .burger-icon {
            display: none;
            flex-direction: column;
            gap: 5px;
            cursor: pointer;
            background: none;
            border: none;
            padding: 4px;
        }

        .burger-icon span {
            width: 25px;
            height: 3px;
            background-color: #ffffff;
            border-radius: 2px;
            transition: all 0.3s ease;
        }

        /* Mobile Nav Dropdown */
        @media (max-width: 768px) {
            .burger-icon { display: flex; }
            .nav-links {
                display: none;
                position: absolute;
                top: 100%;
                right: 0;
                left: 0;
                background-color: var(--primary-hover);
                flex-direction: column;
                padding: 16px 24px;
                gap: 14px;
                box-shadow: 0 10px 15px rgba(0,0,0,0.1);
            }
            .nav-links.show { display: flex; }
        }

        /* Main Article Layout */
        .article-container {
            max-width: 850px;
            margin: 32px auto;
            padding: 0 16px;
        }

        .article-card {
            background: var(--card-bg);
            padding: 36px 30px;
            border-radius: var(--radius);
            box-shadow: 0 10px 30px rgba(0,0,0,0.04);
            border: 1px solid var(--border);
        }

        .article-header {
            background-color: var(--primary);
            color: #ffffff;
            box-shadow: 0 4px 20px rgba(0,0,0,0.08);
            margin-bottom: 24px;
            border-bottom: 1px solid var(--border);
            padding-bottom: 20px; 
        }

        .article-category {
            display: inline-block;
            background: #f0fdf4;
            color: var(--primary);
            padding: 4px 12px;
            border-radius: 20px;
            font-size: 0.85rem;
            font-weight: 700;
            margin-bottom: 12px;
            margin: 10px;
        }

        .article-title {
            font-size: 1.4rem;
            color: #fff;
            line-height: 1.3;
            margin-bottom: 12px;
            margin: 10px;
        }

        .article-meta {
            font-size: 0.60rem;
            color: #fff;
            display: flex;
            gap: 16px;
            margin: 10px;
        }

        /* Table of Contents */
        .toc-box {
            background: #f8fafc;
            border: 1px solid var(--border);
            border-radius: 12px;
            padding: 18px 22px;
            margin: 24px 0;
        }

        .toc-title {
            font-weight: 700;
            color: var(--primary);
            margin-bottom: 8px;
            font-size: 1rem;
        }

        .toc-list {
            padding-right: 20px;
            font-size: 0.93rem;
        }

        .toc-list a {
            color: #334155;
            text-decoration: none;
        }

        .toc-list a:hover {
            color: var(--accent);
            text-decoration: underline;
        }

        /* Article Typography */
        .article-body h2 {
            color: var(--primary);
            font-size: 1.4rem;
            margin: 32px 0 14px 0;
            scroll-margin-top: 80px;
        }

        .article-body h3 {
            color: #334155;
            font-size: 1.15rem;
            margin: 20px 0 10px 0;
        }

        .article-body p {
            font-size: 1.02rem;
            color: #475569;
            margin-bottom: 16px;
        }

        .article-body ul, .article-body ol {
            padding-right: 24px;
            margin-bottom: 16px;
            color: #475569;
        }

        /* Calculator CTA Box Inside Article */
        .cta-box {
            background: linear-gradient(135deg, #1b4d3e, #143d31);
            color: #ffffff;
            padding: 24px;
            border-radius: 14px;
            text-align: center;
            margin: 36px 0;
            box-shadow: 0 8px 20px rgba(27, 77, 62, 0.15);
        }

        .cta-box h3 {
            color: #ffffff;
            font-size: 1.3rem;
            margin-bottom: 8px;
        }

        .cta-box p {
            color: #e2e8f0;
            font-size: 0.92rem;
            margin-bottom: 16px;
        }

        .cta-btn {
            display: inline-block;
            background: var(--accent);
            color: #ffffff;
            padding: 12px 28px;
            border-radius: 10px;
            text-decoration: none;
            font-weight: 700;
            font-size: 1rem;
            transition: transform 0.2s, background 0.2s;
        }

        .cta-btn:hover {
            background: #d35400;
            transform: translateY(-2px);
        }

        /* Footer */
        footer {
            background-color: #0f2d24;
            color: #94a3b8;
            padding: 32px 16px;
            text-align: center;
            font-size: 0.88rem;
            margin-top: 60px;
        }

         /* Footer & Modal */
        footer {
            background-color: #0f2d24;
            color: #94a3b8;
            padding: 32px 16px;
            text-align: center;
            font-size: 0.88rem;
            margin-top: 60px;
        }

        footer a {
            color: #cbd5e1;
            text-decoration: underline;
            margin: 0 10px;
            cursor: pointer;
        }

        .modal-overlay {
            position: fixed;
            top: 0; left: 0; right: 0; bottom: 0;
            background: rgba(15, 23, 42, 0.65);
            backdrop-filter: blur(4px);
            display: flex;
            justify-content: center;
            align-items: center;
            z-index: 1000;
            padding: 20px;
            opacity: 0;
            pointer-events: none;
            transition: opacity 0.25s ease;
        }

        .modal-overlay.active { opacity: 1; pointer-events: auto; }

        .modal-card {
            background: #ffffff;
            padding: 28px;
            border-radius: var(--radius);
            max-width: 480px;
            width: 100%;
        }

        .close-btn {
            width: 100%;
            padding: 10px;
            background: var(--primary);
            color: #ffffff;
            border: none;
            border-radius: 8px;
            font-weight: 600;
            cursor: pointer;
            margin-top: 16px;
        }