body {
    font-family: Arial, sans-serif;
    margin: 0;
    padding: 0;
    display: flex;
    justify-content: center;
    align-items: center;

    background-color: #f4f4f9;
}

#app {
    background: #ffffff;
    padding: 20px;
    border-radius: 10px;
    box-shadow: 0 4px 10px rgba(0, 0, 0, 0.2);
    max-width: 500px;
    width: 100%;
}

h1 {
    text-align: center;
    font-size: 1.5em;
    color: #333;
}

#problem-container {
    margin: 20px 0;
}

#problem {
    font-size: 1.2em;
    color: #444;
    text-align: center;
}

input {
    width: calc(100% - 20px);
    padding: 10px;
    margin: 10px 0;
    border: 1px solid #ccc;
    border-radius: 5px;
    font-size: 1em;
}

button {
    width: 100%;
    padding: 10px;
    background-color: #007BFF;
    color: white;
    border: none;
    border-radius: 5px;
    font-size: 1em;
    cursor: pointer;
    transition: background-color 0.3s ease;
}

button:hover {
    background-color: #0056b3;
}

#feedback {
    font-size: 1.1em;
    font-weight: bold;
    text-align: center;
    margin: 10px 0;
}

#solution-container {
    margin-top: 20px;
    background: #f9f9f9;
    padding: 10px;
    border: 1px solid #ddd;
    border-radius: 5px;
}