body {
    transition: background-color 0.5s, color 0.5s;
}

header, nav, .scientist-card {
    transition: background-color 0.5s, color 0.5s;
}

body.dark-mode {
    background-color: #121212;
    color: #e0e0e0;
}

header.dark-mode, nav.dark-mode, .scientist-card.dark-mode {
    background-color: #1e1e1e;
    color: #e0e0e0;
}