/* a > div       { display: none; }
a:hover > div { display: block; } */

.centered               { text-align: center;   }
.hover_img a            { position:   relative; }
.hover_img a span       { z-index:    99;
                          display:    none;
                          position:   absolute; }
.hover_img a:hover span { display:    block;    }
.derived                { color:      blue;     }
.adaptation             { color:      red;      }
.extension              { color:      maroon;   }