:root {
            --primary: #4361ee;
            --secondary: #3a0ca3;
            --accent: #7209b7;
            --light: #f8f9fa;
            --dark: #212529;
            --success: #4cc9f0;
            --gradient-start: #4361ee;
            --gradient-end: #3a0ca3;
            --card-bg: rgba(255, 255, 255, 0.95);
            --shadow: 0 8px 32px rgba(31, 38, 135, 0.15);
            --transition: all 0.3s ease;
        }

        * {
            margin: 0;
            padding: 0;
            box-sizing: border-box;
            font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
        }

        body {
            background: linear-gradient(135deg, #f5f7fa 0%, #c3cfe2 100%);
            color: var(--dark);
            line-height: 1.6;
            min-height: 100vh;
            padding-bottom: 2rem;
        }

        .container {
            max-width: 1200px;
            margin: 0 auto;
            padding: 0 20px;
        }

        header {
            background: linear-gradient(120deg, var(--gradient-start), var(--gradient-end));
            color: white;
            padding: 1.5rem 0;
            box-shadow: var(--shadow);
            position: relative;
            overflow: hidden;
        }

        header::before {
            content: '';
            position: absolute;
            top: -50%;
            left: -50%;
            width: 200%;
            height: 200%;
            background: radial-gradient(circle, rgba(255,255,255,0.1) 0%, rgba(255,255,255,0) 60%);
            transform: rotate(30deg);
        }

        .header-content {
            display: flex;
            justify-content: space-between;
            align-items: center;
            position: relative;
            z-index: 1;
        }

        .logo {
            display: flex;
            align-items: center;
            gap: 10px;
        }

        .logo-icon {
            font-size: 2rem;
            background: white;
            color: var(--primary);
            width: 50px;
            height: 50px;
            border-radius: 50%;
            display: flex;
            align-items: center;
            justify-content: center;
        }

        .logo-text {
            font-size: 1.8rem;
            font-weight: 700;
        }

        nav ul {
            display: flex;
            list-style: none;
            gap: 1.5rem;
        }

        nav a {
            color: white;
            text-decoration: none;
            font-weight: 500;
            transition: var(--transition);
            padding: 5px 10px;
            border-radius: 20px;
        }

        nav a:hover {
            background: rgba(255, 255, 255, 0.2);
        }

        .hero {
            text-align: center;
            padding: 3rem 0;
            background: url('https://images.unsplash.com/photo-1531297484001-80022131f5a1?ixlib=rb-4.0.3&auto=format&fit=crop&w=1200&q=80') no-repeat center center/cover;
            position: relative;
            color: white;
            margin-bottom: 2rem;
            border-radius: 0 0 15px 15px;
            overflow: hidden;
        }

        .hero::before {
            content: '';
            position: absolute;
            top: 0;
            left: 0;
            width: 100%;
            height: 100%;
            background: linear-gradient(120deg, rgba(67, 97, 238, 0.8), rgba(58, 12, 163, 0.8));
        }

        .hero-content {
            position: relative;
            z-index: 1;
            max-width: 800px;
            margin: 0 auto;
        }

        .hero h1 {
            font-size: 2.8rem;
            margin-bottom: 1rem;
            font-weight: 800;
        }

        .hero p {
            font-size: 1.2rem;
            margin-bottom: 2rem;
            opacity: 0.9;
        }

        .converter-container {
            display: grid;
            grid-template-columns: 1fr 2fr;
            gap: 2rem;
            margin-top: -50px;
            position: relative;
            z-index: 2;
        }

        @media (max-width: 768px) {
            .converter-container {
                grid-template-columns: 1fr;
            }
        }

        .categories {
            background: var(--card-bg);
            border-radius: 15px;
            padding: 1.5rem;
            box-shadow: var(--shadow);
            height: fit-content;
            max-height: 600px;
            overflow-y: auto;
        }

        .categories h2 {
            margin-bottom: 1.2rem;
            color: var(--primary);
            font-size: 1.5rem;
            display: flex;
            align-items: center;
            gap: 10px;
            position: sticky;
            top: 0;
            background: var(--card-bg);
            padding: 10px 0;
            z-index: 1;
        }

        .category-list {
            display: grid;
            grid-template-columns: repeat(auto-fill, minmax(120px, 1fr));
            gap: 0.8rem;
        }

        .category-btn {
            background: white;
            border: 1px solid #e2e8f0;
            padding: 12px 10px;
            border-radius: 10px;
            text-align: center;
            cursor: pointer;
            transition: var(--transition);
            font-weight: 500;
            display: flex;
            flex-direction: column;
            align-items: center;
            gap: 5px;
        }

        .category-btn:hover, .category-btn.active {
            background: var(--primary);
            color: white;
            border-color: var(--primary);
            transform: translateY(-3px);
            box-shadow: 0 5px 15px rgba(67, 97, 238, 0.3);
        }

        .category-icon {
            font-size: 1.5rem;
        }

        .converter {
            background: var(--card-bg);
            border-radius: 15px;
            padding: 2rem;
            box-shadow: var(--shadow);
        }

        .converter-header {
            display: flex;
            justify-content: space-between;
            align-items: center;
            margin-bottom: 1.5rem;
            flex-wrap: wrap;
            gap: 1rem;
        }

        .converter-title {
            font-size: 1.8rem;
            color: var(--primary);
        }

        .decimal-control {
            display: flex;
            align-items: center;
            gap: 10px;
        }

        .decimal-control label {
            font-weight: 600;
        }

        .decimal-control select {
            padding: 8px 12px;
            border-radius: 6px;
            border: 1px solid #e2e8f0;
        }

        .converter-body {
            display: grid;
            grid-template-columns: 1fr 1fr;
            gap: 1.5rem;
        }

        @media (max-width: 576px) {
            .converter-body {
                grid-template-columns: 1fr;
            }
        }

        .input-group, .output-group {
            display: flex;
            flex-direction: column;
            gap: 0.8rem;
        }

        label {
            font-weight: 600;
            color: var(--dark);
        }

        input, select {
            padding: 12px 15px;
            border: 1px solid #e2e8f0;
            border-radius: 8px;
            font-size: 1rem;
            transition: var(--transition);
        }

        input:focus, select:focus {
            outline: none;
            border-color: var(--primary);
            box-shadow: 0 0 0 3px rgba(67, 97, 238, 0.2);
        }

        input {
            background: #f8f9fa;
        }

        .output {
            background: #f8f9fa;
            padding: 12px 15px;
            border-radius: 8px;
            min-height: 46px;
            border: 1px solid #e2e8f0;
            font-size: 1.1rem;
            font-weight: 600;
            color: var(--primary);
            display: flex;
            align-items: center;
        }

        .swap-btn {
            align-self: center;
            background: var(--accent);
            color: white;
            border: none;
            width: 40px;
            height: 40px;
            border-radius: 50%;
            display: flex;
            align-items: center;
            justify-content: center;
            cursor: pointer;
            transition: var(--transition);
            margin-top: 1.8rem;
        }

        .swap-btn:hover {
            transform: rotate(180deg);
            background: var(--secondary);
        }

        .features {
            margin: 4rem 0;
        }

        .section-title {
            text-align: center;
            margin-bottom: 2.5rem;
            color: var(--primary);
            font-size: 2.2rem;
        }

        .feature-grid {
            display: grid;
            grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
            gap: 2rem;
        }

        .feature-card {
            background: var(--card-bg);
            border-radius: 15px;
            padding: 1.5rem;
            box-shadow: var(--shadow);
            transition: var(--transition);
        }

        .feature-card:hover {
            transform: translateY(-5px);
            box-shadow: 0 15px 30px rgba(31, 38, 135, 0.15);
        }

        .feature-icon {
            font-size: 2.5rem;
            color: var(--primary);
            margin-bottom: 1rem;
        }

        .feature-title {
            font-size: 1.3rem;
            margin-bottom: 0.8rem;
            color: var(--dark);
        }

        footer {
            text-align: center;
            margin-top: 4rem;
            padding: 2rem 0;
            color: var(--dark);
            opacity: 0.8;
        }

        /* 响应式设计 */
        @media (max-width: 768px) {
            .header-content {
                flex-direction: column;
                gap: 1rem;
            }
            
            nav ul {
                flex-wrap: wrap;
                justify-content: center;
            }
            
            .hero h1 {
                font-size: 2.2rem;
            }
            
            .category-list {
                grid-template-columns: repeat(3, 1fr);
            }
        }

        @media (max-width: 480px) {
            .logo-text {
                font-size: 1.5rem;
            }
            
            .hero h1 {
                font-size: 1.8rem;
            }
            
            .category-list {
                grid-template-columns: repeat(2, 1fr);
            }
            
            .converter-header {
                flex-direction: column;
                align-items: flex-start;
                gap: 1rem;
            }
        }
        
        .friend-links-container {
            width: 100%;
        }
        
        .friend-links {
            display: flex;
            flex-wrap: wrap;
            justify-content: center;
            gap: 1rem;
            max-width: 1200px;
            margin: 0 auto;
        }
        
        .friend-links a {
            color: #333;
            text-decoration: none;
            font-size: 0.95rem;
            transition: all 0.3s ease;
            border-radius: 4px;
        }
        
        .friend-links a:hover {
            color: #007bff;
            transform: translateY(-2px);
        }
        
        @media (max-width: 768px) {
            .friend-links {
                gap: 1rem;
                padding: 0.5rem;
            }
            
            .friend-links a {
                font-size: 0.85rem;
            }
        }

	
        .logo-image {
    height: 40px;
        }