* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    min-height: 100vh;
    padding: 20px;
    color: #333;
}

.container {
    max-width: 800px;
    margin: 0 auto;
    background: white;
    border-radius: 20px;
    padding: 40px;
    box-shadow: 0 20px 60px rgba(0, 0, 0, 0.3);
}

h1 {
    color: #667eea;
    font-size: 2.5em;
    margin-bottom: 10px;
    text-align: center;
}

.description {
    text-align: center;
    color: #666;
    margin-bottom: 40px;
    font-size: 1.1em;
}

.download-section {
    margin-bottom: 40px;
    padding: 30px;
    background: #f8f9fa;
    border-radius: 15px;
    border: 2px solid #e9ecef;
}

.download-section h2 {
    color: #495057;
    margin-bottom: 20px;
    font-size: 1.5em;
}

.button-group {
    display: flex;
    flex-wrap: wrap;
    gap: 15px;
}

.download-btn {
    padding: 12px 24px;
    font-size: 16px;
    font-weight: 600;
    color: white;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    border: none;
    border-radius: 8px;
    cursor: pointer;
    transition: all 0.3s ease;
    box-shadow: 0 4px 15px rgba(102, 126, 234, 0.4);
}

.download-btn:hover {
    transform: translateY(-2px);
    box-shadow: 0 6px 20px rgba(102, 126, 234, 0.6);
}

.download-btn:active {
    transform: translateY(0);
}

.download-btn.primary {
    background: linear-gradient(135deg, #f093fb 0%, #f5576c 100%);
    box-shadow: 0 4px 15px rgba(245, 87, 108, 0.4);
}

.download-btn.primary:hover {
    box-shadow: 0 6px 20px rgba(245, 87, 108, 0.6);
}

.custom-download {
    display: flex;
    gap: 10px;
    flex-wrap: wrap;
}

.url-input {
    flex: 1;
    min-width: 200px;
    padding: 12px 16px;
    font-size: 16px;
    border: 2px solid #e9ecef;
    border-radius: 8px;
    transition: border-color 0.3s ease;
}

.url-input:focus {
    outline: none;
    border-color: #667eea;
}

.info-section {
    background: #e7f3ff;
    padding: 25px;
    border-radius: 15px;
    border-left: 4px solid #667eea;
}

.info-section h2 {
    color: #495057;
    margin-bottom: 15px;
    font-size: 1.3em;
}

.info-section ul {
    list-style-position: inside;
    color: #495057;
    line-height: 1.8;
}

.info-section li {
    margin-bottom: 8px;
}

/* Loading 样式 */
.loading-overlay {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(0, 0, 0, 0.6);
    display: none;
    justify-content: center;
    align-items: center;
    z-index: 9999;
    backdrop-filter: blur(4px);
    animation: fadeIn 0.3s ease;
}

.loading-overlay.show {
    display: flex;
}

.loading-content {
    background: white;
    padding: 40px 50px;
    border-radius: 15px;
    box-shadow: 0 10px 40px rgba(0, 0, 0, 0.3);
    text-align: center;
    animation: slideUp 0.3s ease;
}

.spinner {
    width: 50px;
    height: 50px;
    border: 4px solid #f3f3f3;
    border-top: 4px solid #667eea;
    border-radius: 50%;
    animation: spin 1s linear infinite;
    margin: 0 auto 20px;
}

.loading-text {
    color: #495057;
    font-size: 16px;
    font-weight: 500;
    margin: 0;
}

@keyframes spin {
    0% { transform: rotate(0deg); }
    100% { transform: rotate(360deg); }
}

@keyframes fadeIn {
    from {
        opacity: 0;
    }
    to {
        opacity: 1;
    }
}

@keyframes slideUp {
    from {
        transform: translateY(20px);
        opacity: 0;
    }
    to {
        transform: translateY(0);
        opacity: 1;
    }
}

/* 响应式设计 */
@media (max-width: 600px) {
    .container {
        padding: 20px;
    }

    h1 {
        font-size: 2em;
    }

    .button-group {
        flex-direction: column;
    }

    .download-btn {
        width: 100%;
    }

    .custom-download {
        flex-direction: column;
    }

    .url-input {
        width: 100%;
    }

    .loading-content {
        padding: 30px 40px;
        margin: 20px;
    }
}

.top-nav {
    max-width: 800px;
    margin: 0 auto 20px;
    display: flex;
    gap: 12px;
    justify-content: center;
    align-items: center;
    padding: 12px 20px;
    background: rgba(255, 255, 255, 0.85);
    border-radius: 14px;
    box-shadow: 0 12px 40px rgba(0, 0, 0, 0.15);
    backdrop-filter: blur(10px);
}

.nav-link {
    padding: 10px 22px;
    border-radius: 999px;
    font-weight: 600;
    color: #667eea;
    text-decoration: none;
    transition: all 0.3s ease;
}

.nav-link:hover {
    background: rgba(102, 126, 234, 0.15);
    color: #4c63d2;
}

.nav-link.active {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: #fff;
    box-shadow: 0 6px 18px rgba(102, 126, 234, 0.45);
}