#difficulty-filter {
    display: flex;
    justify-content: center;
    align-items: center;
    gap: 8px;
    margin: 0.25rem auto 0;
    padding: 6px 14px;
    background: #f4f3f9;
    border: 1px solid #dee2e6;
    border-radius: 8px;
    width: fit-content;
}

.filter-label {
    font-size: 0.8rem;
    color: #495057;
    font-weight: 500;
}

.diff-btn {
    padding: 4px 14px;
    border: 1.5px solid #c5c0e0;
    border-radius: 6px;
    background: #fff;
    color: #6c757d;
    font-size: 0.85rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.15s;
}

.diff-btn:hover {
    border-color: #362A8D;
    color: #362A8D;
    background: #fff;
}

.diff-btn.active {
    background: #362A8D;
    border-color: #362A8D;
    color: white;
}

#problem-prompt {
    text-align: center;
    font-size: 1.1rem;
    margin: 1rem 0;
    color: #495057;
    font-weight: 500;
}

#newman-container {
    display: flex;
    justify-content: center;
    margin: 1rem auto;
    max-width: 340px;
}

#newman-svg {
    width: 100%;
    height: auto;
}

/* Newman diagram elements */
.newman-back-circle {
    fill: none;
    stroke: #333;
    stroke-width: 2;
}

.newman-front-dot {
    fill: #333;
}

.newman-bond {
    stroke: #333;
    stroke-width: 2;
}

.newman-bond.back {
    stroke: #666;
}

.newman-label {
    font-family: Arial, Helvetica, sans-serif;
    font-size: 17px;
    dominant-baseline: central;
    fill: #333;
}

.newman-label.back {
    fill: #666;
}

/* Conformation choice buttons */
#conformation-choices {
    display: flex;
    justify-content: center;
    gap: 8px;
    flex-wrap: wrap;
    margin: 1rem 0;
}

.conf-btn {
    padding: 10px 20px;
    font-size: 1rem;
    min-width: 120px;
}

.conf-btn.correct-choice {
    background-color: #28a745;
    color: white;
}

.conf-btn.incorrect-choice {
    background-color: #dc3545;
    color: white;
}

.conf-btn:disabled {
    opacity: 0.7;
}