.square, .circle {
  width: 100px;
  height: 100px;
  display: inline-block;
  float: left;
}
.circle {
  border-radius: 50%;
}

#container{
  background-color: black;
  margin: 0px auto;
  padding: 0px;
  width: 600px;
  height: 600px;
}

#blockPink{
  background-color: pink;
}
#blockYellow{
  background-color: yellow;
}
#blockBlue{
  background-image:url('ocean.jpg')
}