/* ── RESEARCH SECTION ── */
.research-section {
        padding: 2rem 1rem;
        margin-top: 150px;
}

.research-section h2 {
        text-align: center;
        font-size: 2rem;
        margin-bottom: 1.5rem;
        color: var(--primary-color);
}

/* grid of topic cards */
.interest-grid {
        display: grid;
        grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
        gap: 1rem;
}

/* each topic card */
.interest-card {
        background: #fff;
        border: 1px solid #eee;
        border-radius: 8px;
        padding: 1rem;
        box-shadow: 0 1px 4px rgba(0, 0, 0, 0.05);
}

.interest-card h3 {
        margin: 0 0 0.75rem;
        font-size: 1.125rem;
        color: #222;
}

/* row of teacher thumbnails */
.teacher-thumbs {
        display: flex;
        flex-wrap: wrap;
        gap: 0.5rem;
}

/* circular thumbnail */
.profile-thumb {
        width: 40px;
        height: 40px;
        border-radius: 50%;
        object-fit: cover;
        cursor: pointer;
        border: 2px solid #fff;
        box-shadow: 0 1px 3px rgba(0, 0, 0, 0.2);
}

/* tooltip wrapper */
.tooltip {
        position: relative;
        display: inline-block;
}

/* hidden by default */
.tooltiptext {
        visibility: hidden;
        width: max-content;
        background-color: rgba(0, 0, 0, 0.75);
        color: #fff;
        text-align: center;
        padding: 4px 8px;
        border-radius: 4px;
        position: absolute;
        z-index: 20;
        bottom: 125%;
        /* above the image */
        left: 50%;
        transform: translateX(-50%);
        opacity: 0;
        transition: opacity 0.2s ease-in-out;
}

.tooltip:hover .tooltiptext {
        visibility: visible;
        opacity: 1;
}

/* ── Responsive Tweaks ── */
@media (max-width: 768px) {
        .nav-list {
                flex-wrap: wrap;
                gap: 1rem;
        }

        .interest-grid {
                grid-template-columns: repeat(auto-fit, minmax(160px, 1fr));
        }     }