body {
    background-color: white;
    color: black;
    font-family: Arial, sans-serif;
    font-size: 24px;
    margin: 0;
    padding: 20px;
}

#container {
    max-width: 800px;
    margin: 0 auto;
}

.output {
    margin: 15px 0;
}

.big {
    font-size: 48px;
}

.output.correct {
    color: darkgreen;
}

.output.wrong {
    color: darkred;
}

.options {
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
    gap: 10px;
    margin: 20px 0;
}

.options button {
    padding: 15px 30px;
    font-size: 24px;
    cursor: pointer;
    background-color: lightblue;
    border: none;
    border-radius: 10px;
}

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

.options button.selected {
    background-color: lightyellow;
}

.options button.selected:disabled {
    background-color: lightyellow;
    opacity: 1;
}