.tile{
  width:100%;
  height:100px;
  border: 5px solid black;
  margin: 5px;
  border-radius: 15%;
  display: inline-block;
}

main{
  width: 1000px;
  margin: auto 0;
  background-color: blue;
  padding: 10px;
}

.tile:hover{
  background-color: red;

}