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

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    line-height: 1.6;
    color: #333;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    min-height: 100vh;
}

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

/* 导航栏样式 */
.navbar {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 40px;
}

.nav-brand h1 {
    color: white;
    font-size: 2rem;
}

.language-selector {
    padding: 8px 16px;
    border: none;
    border-radius: 6px;
    background: white;
    color: #333;
    cursor: pointer;
}

/* 主要内容区域 */
.main-content {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 30px;
}

.upload-card {
    background: white;
    padding: 40px;
    border-radius: 15px;
    box-shadow: 0 10px 30px rgba(0, 0, 0, 0.2);
    text-align: center;
    width: 100%;
    max-width: 600px;
}

.upload-icon {
    font-size: 3rem;
    margin-bottom: 20px;
}

.upload-card h2 {
    margin-bottom: 10px;
    color: #333;
}

.upload-card p {
    color: #666;
    margin-bottom: 30px;
}

/* 上传区域样式 */
.upload-area {
    border: 2px dashed #ddd;
    border-radius: 10px;
    padding: 40px;
    margin-bottom: 20px;
    cursor: pointer;
    transition: all 0.3s ease;
}

.upload-area:hover {
    border-color: #667eea;
    background: #f8f9ff;
}

.upload-area.dragover {
    border-color: #667eea;
    background: #f0f4ff;
}

.upload-icon-large {
    font-size: 4rem;
    margin-bottom: 15px;
}

.file-info {
    margin-bottom: 20px;
}

.file-details {
    display: flex;
    justify-content: space-between;
    align-items: center;
    background: #f8f9fa;
    padding: 15px;
    border-radius: 8px;
    border-left: 4px solid #667eea;
}

.btn-remove {
    background: none;
    border: none;
    font-size: 1.5rem;
    cursor: pointer;
    color: #666;
}

.btn-remove:hover {
    color: #ff4757;
}

/* 转换选项 */
.conversion-options {
    text-align: left;
    margin-bottom: 30px;
}

.option-label {
    display: block;
    margin-bottom: 10px;
    font-weight: 600;
}

.format-options {
    display: flex;
    gap: 20px;
}

.radio-option {
    display: flex;
    align-items: center;
    gap: 8px;
    cursor: pointer;
}

/* 按钮样式 */
.btn-convert {
    background: linear-gradient(135deg, #667eea, #764ba2);
    color: white;
    border: none;
    padding: 15px 40px;
    border-radius: 8px;
    font-size: 1.1rem;
    cursor: pointer;
    transition: all 0.3s ease;
    width: 100%;
}

.btn-convert:hover:not(:disabled) {
    transform: translateY(-2px);
    box-shadow: 0 5px 15px rgba(102, 126, 234, 0.4);
}

.btn-convert:disabled {
    background: #ccc;
    cursor: not-allowed;
    transform: none;
}

/* 结果区域样式 */
.result-card {
    background: white;
    padding: 40px;
    border-radius: 15px;
    box-shadow: 0 10px 30px rgba(0, 0, 0, 0.2);
    width: 100%;
    max-width: 800px;
}

.result-header {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 15px;
    margin-bottom: 30px;
}

.success-icon {
    font-size: 2rem;
}

/* 表格预览 */
.preview-section {
    margin-bottom: 30px;
}

.preview-section h4 {
    margin-bottom: 15px;
    color: #333;
}

.table-container {
    max-height: 400px;
    overflow: auto;
    border: 1px solid #ddd;
    border-radius: 8px;
}

table {
    width: 100%;
    border-collapse: collapse;
}

th, td {
    padding: 12px;
    text-align: left;
    border-bottom: 1px solid #ddd;
}

th {
    background: #f8f9fa;
    font-weight: 600;
    position: sticky;
    top: 0;
}

tr:hover {
    background: #f8f9fa;
}

/* 下载按钮 */
.download-actions {
    display: flex;
    gap: 15px;
    justify-content: center;
}

.btn-download {
    background: linear-gradient(135deg, #00b894, #00a085);
    color: white;
    border: none;
    padding: 12px 30px;
    border-radius: 8px;
    cursor: pointer;
    transition: all 0.3s ease;
}

.btn-secondary {
    background: #6c757d;
    color: white;
    border: none;
    padding: 12px 30px;
    border-radius: 8px;
    cursor: pointer;
    transition: all 0.3s ease;
}

.btn-download:hover, .btn-secondary:hover {
    transform: translateY(-2px);
    box-shadow: 0 5px 15px rgba(0, 0, 0, 0.2);
}

/* 加载动画 */
.loading-section {
    text-align: center;
    color: white;
}

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

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

/* 特性介绍 */
.features-section {
    margin-top: 60px;
    text-align: center;
    color: white;
}

.features-section h2 {
    margin-bottom: 40px;
    font-size: 2rem;
}

.features-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 30px;
}

.feature-card {
    background: rgba(255, 255, 255, 0.1);
    padding: 30px;
    border-radius: 15px;
    backdrop-filter: blur(10px);
}

.feature-icon {
    font-size: 3rem;
    margin-bottom: 20px;
}

.feature-card h3 {
    margin-bottom: 15px;
}

/* 响应式设计 */
@media (max-width: 768px) {
    .container {
        padding: 10px;
    }
    
    .upload-card, .result-card {
        padding: 20px;
    }
    
    .download-actions {
        flex-direction: column;
    }
    
    .features-grid {
        grid-template-columns: 1fr;
    }
    
    .navbar {
        flex-direction: column;
        gap: 15px;
    }
}