*{
  font-family: Avenir, sans-serif;
  font-size: 1em;
  text-align: center;
  margin: 0px;
  padding: 0px;
  box-sizing: border-box;
}

.conteneur{
  width: 90%;
  margin: 10px;
  border: 2px dashed black;
}
.conteneur-flex{
  display: flex;
  flex-flow: row wrap;
  margin: -10px;
}
.conteneur-flex > div{
  flex: 0 0 25%;
  padding: 20px 0px;
  margin: 10px;
  background-color: gold;
  border: 2px solid RGB(120,40,160);
}