.expression {
    text-align: center;
    font-size: 36px;
    font-weight: bold;
    color: #333;
    margin-bottom: 30px;
}

.expression input {
    width: 80px;
    padding: 8px;
    font-size: 24px;
    text-align: center;
    border: 2px solid #4caf50;
    border-radius: 5px;
}

.score {
    text-align: center;
    font-size: 18px;
    color: #555;
    margin-bottom: 20px;
}

.correct {
    text-align: center;
    font-size: 20px;
    font-weight: bold;
    color: white;
    background-color: #4caf50;
    padding: 10px;
    border-radius: 5px;
    margin-bottom: 20px;
}

.incorrect {
    text-align: center;
    font-size: 20px;
    font-weight: bold;
    color: white;
    background-color: #f44336;
    padding: 10px;
    border-radius: 5px;
    margin-bottom: 20px;
}

button {
    width: 100%;
    padding: 12px;
    background-color: #4caf50;
    color: white;
    border: none;
    border-radius: 5px;
    font-size: 18px;
    font-weight: bold;
    cursor: pointer;
    margin-top: 20px;
}

button:hover {
    background-color: #274829;
}

a {
    display: block;
    text-align: center;
    margin-top: 20px;
    font-size: 18px;
    color: #4caf50;
    font-weight: bold;
}