* {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: Arial;
}

.header {
  text-align: center;
  padding: 32px;
}

#listado_temas {
    width: 22%;
    min-width: 200px;
    float: left;
    border: 1px solid #dedede;
    margin-top: 10px;
    margin-left: 10px;
    margin-bottom: 10px;
    text-align: center;
}

#grid {
  display: -ms-flexbox; /* IE10 */
  display: flex;
  -ms-flex-wrap: wrap; /* IE10 */
  flex-wrap: wrap;
  padding: 30px 4px 30px 4px;
}

/* Create four equal columns that sits next to each other */
.column {
  -ms-flex: 33.3%; /* IE10 */
  flex: 33.3%;
  max-width: 33.3%;
  padding: 0 4px;
}

.column img {
  margin-top: 8px;
  vertical-align: middle;
  width: 100%;
}

.cell {
    position: relative;
    border: 1px solid #dedede;
    margin-top: 10px;
    height: 212px;
}

.cell_title {
    height: 60%;
    width: 100%;
    background-color: rgba(255,255,255,.8);
    position: absolute;
    color: #05a1a0;
    font-size: 18px;
    font-weight: bold;
    padding: 10px;
}

.cell img {
  width: 98%; 
  margin: 1%; 
  height: 98%;
}

.filter {
    margin: 4px;
    display: inline-block;
    font-size: 14px;
    font-weight: normal;
}

/* Responsive layout - makes a two column-layout instead of four columns */
@media screen and (max-width: 991px) {
  .column {
    -ms-flex: 50%;
    flex: 50%;
    max-width: 50%;
  }
}

/* Responsive layout - makes the two columns stack on top of each other instead of next to each other */
@media screen and (max-width: 600px) {
  .column {
    -ms-flex: 100%;
    flex: 100%;
    max-width: 100%;
  }
  #listado_temas {
    width: 100%;
  }
}