body {
    font-family: Arial, sans-serif;
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    background-color: #f0f0f0;
    margin: 0;
}

.container {
    background-color: #ffffff;
    padding: 20px;
    border-radius: 10px;
    box-shadow: 0 4px 8px rgba(0, 0, 0, 0.1);
    text-align: center;
    width: 90%;
    max-width: 500px;
}

h1 {
    color: #333;
}

.quiz-box {
    margin-top: 20px;
}

#score-counter {
    font-size: 1.2em;
    font-weight: bold;
    color: #0056b3;
    margin-bottom: 10px;
    text-align: right;
    padding-right: 10px;
}

#question {
    font-size: 2em;
    margin-bottom: 20px;
    color: #555;
}

#answer-buttons {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 10px;
    margin-bottom: 20px;
}

.btn {
    background-color: #007bff;
    color: white;
    border: none;
    padding: 15px;
    font-size: 1.2em;
    border-radius: 5px;
    cursor: pointer;
    transition: background-color 0.3s;
}

.btn:hover {
    background-color: #0056b3;
}

.btn:disabled {
    background-color: #cccccc;
    cursor: not-allowed;
}

#feedback {
    font-size: 1.2em;
    font-weight: bold;
    min-height: 20px;
}

.correct {
    color: green;
}

.incorrect {
    color: red;
}

#next-btn {
    background-color: #28a745;
    color: white;
    border: none;
    padding: 10px 20px;
    font-size: 1em;
    border-radius: 5px;
    cursor: pointer;
    transition: background-color 0.3s;
}

#next-btn.hidden {
    display: none;
}

#next-btn i {
    margin-right: 5px;
}

#next-btn:hover {
    background-color: #218838;
}

#level-selection,
#operation-selection {
    margin-bottom: 20px;
}

#level-selection h3,
#operation-selection h3 {
    margin-bottom: 10px;
    color: #555;
}

.level-btn {
    background-color: #17a2b8;
    color: white;
    border: none;
    padding: 10px 20px;
    font-size: 1em;
    border-radius: 5px;
    cursor: pointer;
    margin: 0 5px;
    transition: background-color 0.3s;
}

.level-btn:hover {
    background-color: #138496;
}

.active-level {
    background-color: #0056b3;
    box-shadow: 0 0 5px rgba(0, 0, 0, 0.5);
    border: 2px solid white;
}

.selection-container {
    display: flex;
    justify-content: space-around;
    margin-bottom: 20px;
}

.choice-btn {
    background-color: #17a2b8;
    color: white;
    border: none;
    padding: 10px 15px;
    margin: 5px;
    border-radius: 5px;
    cursor: pointer;
    transition: background-color 0.3s;
}

.choice-btn:hover {
    background-color: #138496;
}

/* The active state styling for both groups */
.choice-btn.active {
    background-color: #0056b3;
    box-shadow: 0 0 5px rgba(0, 0, 0, 0.5);
    border: 2px solid white;
}