body {
    background: #f5f7fa;
}

.base64-tool-container {
    max-width: 900px;
    margin: 0 auto;
    padding: 2rem;
}

.tabs {
    display: flex;
    gap: 0.5rem;
    margin-bottom: 1.5rem;
    border-bottom: 2px solid #e0e0e0;
    padding-bottom: 0;
}

.tab-btn {
    padding: 1rem 2rem;
    border: none;
    background: transparent;
    color: #666;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s;
    border-bottom: 3px solid transparent;
    margin-bottom: -2px;
}

.tab-btn:hover {
    color: #667eea;
}

.tab-btn.active {
    color: #667eea;
    border-bottom-color: #667eea;
}

.tab-content {
    display: none;
}

.tab-content.active {
    display: block;
}

.input-section,
.output-section {
    background: white;
    border-radius: 16px;
    padding: 1.5rem;
    margin-bottom: 1.5rem;
    box-shadow: 0 4px 20px rgba(0,0,0,0.08);
}

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

.section-header h3 {
    color: #444;
    font-size: 1.3rem;
}

textarea {
    width: 100%;
    min-height: 150px;
    padding: 1rem;
    border: 2px solid #e0e0e0;
    border-radius: 8px;
    font-size: 1rem;
    font-family: inherit;
    resize: vertical;
}

textarea:focus {
    outline: none;
    border-color: #667eea;
    box-shadow: 0 0 0 3px rgba(102,126,234,0.1);
}

textarea[readonly] {
    background: #f8f9fa;
}

.action-bar {
    display: flex;
    justify-content: center;
    gap: 1rem;
    margin-bottom: 1.5rem;
}

.btn {
    padding: 0.8rem 1.5rem;
    border: none;
    border-radius: 8px;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s;
}

.btn:hover {
    transform: translateY(-2px);
}

.btn-primary {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
}

.btn-primary:hover {
    box-shadow: 0 8px 20px rgba(102,126,234,0.3);
}

.btn-secondary {
    background: #f0f0f0;
    color: #666;
}

.btn-secondary:hover {
    background: #e0e0e0;
}

.info-section {
    background: #f0fdf4;
    border: 1px solid #d1fae5;
    border-radius: 12px;
    padding: 1.5rem;
}

.info-section h3 {
    color: #065f46;
    margin-bottom: 1rem;
}

.info-section ul {
    padding-left: 1.5rem;
    margin: 0;
}

.info-section li {
    color: #374151;
    margin-bottom: 0.5rem;
    line-height: 1.6;
}

@media (max-width: 768px) {
    .base64-tool-container {
        padding: 1rem;
    }
    
    .tabs {
        flex-wrap: wrap;
    }
    
    .tab-btn {
        padding: 0.8rem 1.2rem;
        font-size: 0.9rem;
    }
    
    .action-bar {
        flex-direction: column;
    }
    
    .btn {
        width: 100%;
    }
}