/* Single molecule viewer — larger than pKa-pairs two-up layout */
.mol-card {
    display: flex;
    flex-direction: column;
    align-items: center;
}

.viewer-wrap {
    position: relative;
}

#mol-viewer {
    min-height: 300px;
    min-width: 350px;
}

#mol-viewer svg {
    cursor: crosshair;
}

/* pKa overlay shown after answer */
.pka-overlay {
    display: none;
    position: absolute;
    bottom: 8px;
    left: 50%;
    transform: translateX(-50%);
    background: rgba(255, 255, 255, 0.9);
    padding: 2px 10px;
    border-radius: 12px;
    font-size: 0.9rem;
    font-weight: 700;
    color: #c0392b;
    white-space: nowrap;
}

/* Difficulty toggle pills */
#difficulty-toggle {
    display: flex;
    justify-content: center;
    gap: 6px;
    margin-bottom: 1rem;
}

.difficulty-pill {
    padding: 5px 16px;
    border: 2px solid #dee2e6;
    border-radius: 20px;
    cursor: pointer;
    font-size: 0.85rem;
    background: #fff;
    color: #555;
    transition: all 0.15s;
}

.difficulty-pill:hover {
    border-color: #6153cc;
    color: #6153cc;
}

.difficulty-pill.active {
    background: #6153cc;
    border-color: #6153cc;
    color: #fff;
}

/* Hover indicator — translucent teal bubble on mouseover (matches arrow-engine) */
.hover-indicator {
    fill: rgba(42, 157, 143, 0.12);
    stroke: #2a9d8f;
    stroke-width: 1.5;
    opacity: 0.7;
    pointer-events: none;
}

/* Post-answer atom highlights */
.atom-highlight {
    pointer-events: none;
    stroke: none;
    opacity: 0.4;
}

.atom-highlight.correct {
    fill: #28a745;
}

.atom-highlight.incorrect {
    fill: #dc3545;
}

.atom-highlight.revealed {
    fill: #ffc107;
}

/* Compound name shown after answer */
#compound-name {
    text-align: center;
    margin-top: 0.25rem;
    font-size: 0.85rem;
    color: #666;
}