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

body {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    min-height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
    padding: 20px;
}

.container {
    background: white;
    border-radius: 20px;
    box-shadow: 0 20px 60px rgba(0, 0, 0, 0.3);
    width: 100%;
    max-width: 800px;
    overflow: hidden;
}

.header {
    background: linear-gradient(135deg, #2c3e50, #3498db);
    color: white;
    padding: 30px;
    text-align: center;
}

.header h1 {
    font-size: 28px;
    margin-bottom: 10px;
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 15px;
}

.subtitle {
    color: rgba(255, 255, 255, 0.8);
    font-size: 16px;
}

.main-content {
    padding: 30px;
}

.drop-zone {
    border: 3px dashed #3498db;
    border-radius: 15px;
    padding: 50px 20px;
    text-align: center;
    cursor: pointer;
    transition: all 0.3s;
    background: rgba(52, 152, 219, 0.05);
    margin-bottom: 30px;
}

.drop-zone:hover {
    border-color: #2980b9;
    background: rgba(52, 152, 219, 0.1);
}

.drop-zone.drag-over {
    border-color: #2ecc71;
    background: rgba(46, 204, 113, 0.1);
    transform: scale(1.02);
}

.drop-content i {
    font-size: 64px;
    color: #3498db;
    margin-bottom: 20px;
}

.drop-content h3 {
    color: #2c3e50;
    margin-bottom: 10px;
    font-size: 22px;
}

.drop-content p {
    color: #7f8c8d;
    margin-bottom: 5px;
}

.file-types {
    font-size: 14px;
    color: #95a5a6;
    margin-top: 15px;
}

.file-list-section {
    margin-bottom: 30px;
}

.section-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 20px;
}

.section-header h3 {
    color: #2c3e50;
    font-size: 20px;
    display: flex;
    align-items: center;
    gap: 10px;
}

.files-container {
    max-height: 300px;
    overflow-y: auto;
    border: 1px solid #e0e0e0;
    border-radius: 10px;
    padding: 15px;
}

.file-item {
    display: flex;
    align-items: center;
    padding: 15px;
    background: #f8f9fa;
    border-radius: 8px;
    margin-bottom: 10px;
    transition: all 0.3s;
}

.file-item:hover {
    background: #e9ecef;
    transform: translateX(5px);
}

.file-icon {
    width: 40px;
    height: 40px;
    background: #3498db;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    color: white;
    font-size: 18px;
    margin-right: 15px;
}

.file-info {
    flex: 1;
}

.file-name {
    font-weight: 600;
    color: #2c3e50;
    margin-bottom: 5px;
}

.file-size {
    color: #7f8c8d;
    font-size: 14px;
}

.file-remove {
    color: #e74c3c;
    cursor: pointer;
    padding: 8px;
    border-radius: 5px;
    transition: background 0.3s;
}

.file-remove:hover {
    background: rgba(231, 76, 60, 0.1);
}

.action-buttons {
    display: flex;
    gap: 15px;
    justify-content: center;
    margin: 30px 0;
}

.btn {
    padding: 15px 30px;
    border: none;
    border-radius: 10px;
    font-size: 16px;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s;
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 10px;
    min-width: 200px;
}

.btn:disabled {
    opacity: 0.5;
    cursor: not-allowed;
}

.btn:not(:disabled):hover {
    transform: translateY(-3px);
    box-shadow: 0 10px 20px rgba(0, 0, 0, 0.2);
}

.merge-btn {
    background: linear-gradient(135deg, #3498db, #2980b9);
    color: white;
}

.merge-btn:not(:disabled):hover {
    background: linear-gradient(135deg, #2980b9, #1c5f8a);
}

.download-btn {
    background: linear-gradient(135deg, #2ecc71, #27ae60);
    color: white;
}

.download-btn:not(:disabled):hover {
    background: linear-gradient(135deg, #27ae60, #219653);
}

.clear-btn {
    background: #e74c3c;
    color: white;
    padding: 8px 15px;
    font-size: 14px;
    min-width: auto;
}

.clear-btn:hover {
    background: #c0392b;
}

.status-section {
    background: #f8f9fa;
    padding: 20px;
    border-radius: 10px;
    text-align: center;
}

.status-text {
    color: #2c3e50;
    font-size: 18px;
    font-weight: 600;
    margin-bottom: 15px;
}

.progress-container {
    background: #e0e0e0;
    border-radius: 10px;
    height: 10px;
    margin: 15px 0;
    overflow: hidden;
}

.progress-bar {
    background: linear-gradient(90deg, #3498db, #2ecc71);
    height: 100%;
    width: 0%;
    border-radius: 10px;
    transition: width 0.5s ease;
}

.file-count {
    color: #7f8c8d;
    font-size: 14px;
}

.footer {
    text-align: center;
    padding: 20px;
    color: #7f8c8d;
    border-top: 1px solid #e9ecef;
    font-size: 14px;
}

/* Scrollbar styling */
.files-container::-webkit-scrollbar {
    width: 8px;
}

.files-container::-webkit-scrollbar-track {
    background: #f1f1f1;
    border-radius: 4px;
}

.files-container::-webkit-scrollbar-thumb {
    background: #3498db;
    border-radius: 4px;
}

.files-container::-webkit-scrollbar-thumb:hover {
    background: #2980b9;
}

/* Responsive design */
@media (max-width: 768px) {
    .container {
        border-radius: 15px;
    }
    
    .header {
        padding: 20px;
    }
    
    .header h1 {
        font-size: 24px;
        flex-direction: column;
        gap: 10px;
    }
    
    .main-content {
        padding: 20px;
    }
    
    .action-buttons {
        flex-direction: column;
    }
    
    .btn {
        min-width: 100%;
    }
    
    .drop-content i {
        font-size: 48px;
    }
    
    .drop-content h3 {
        font-size: 18px;
    }
}