body {
    font-family: Arial, sans-serif;
    margin: 0;
    background: #f5f5f5;
}

header {
    background: #1a73e8;
    color: white;
    padding: 20px;
    text-align: center;
}

#tool-selector {
    display: flex;
    justify-content: center;
    gap: 15px;
    padding: 20px;
}

#tool-selector button {
    padding: 12px 20px;
    border: none;
    background: #333;
    color: white;
    border-radius: 6px;
    cursor: pointer;
}

#tool-selector button:hover {
    background: #555;
}

#app {
    max-width: 900px;
    margin: 20px auto;
    background: white;
    padding: 25px;
    border-radius: 8px;
    box-shadow: 0 0 10px rgba(0,0,0,0.1);
}