/* (A) WRAPPER */
.hoverwrap {
  position: relative; /* required for (c2) */
}

/* (B) RESPONSIVE IMAGE */
.hoverwrap img { width: 100%; }

/* (C) CAPTION */
.hovercap {
  /* (C1) DIMENSIONS */
  box-sizing: border-box;
  width: 100%;
  padding: 10px;
 
  /* (C2) PLACE AT BOTTOM */
  position: absolute;
  bottom: 0; left: 0;
 
  /* (C3) COLORS */
  background-color: rgba(0, 0, 0, 0.5);
  color: white;
}

/* (D) SHOW/HIDE */
.hovercap {
  visibility: none; opacity: 0;
  transition: opacity 0.1s;
}
.hoverwrap:hover .hovercap {
  visibility: visible; opacity: 1;
}

.hovercap > a{
  text-decoration: none;
  color: #fff;
}