* {
  margin: 0;
  padding: 0;
}

.mainDiv {
  width: 650px;
  height: 550px;
  margin: 6% 0 0 30%;
  background-color: lightgray;
}

.first {
  border: 4px dotted black;
}

.firstDiv {
  width: 125px;
  height: 125px;
  display: inline-block;
  padding: 10px;
  margin: 2% 2% 2% 7%;
}

#div1 {
  background-color: orange;
}
#div2 {
  border-radius: 20px;
  background-color: lightgoldenrodyellow;
}
#div3 {
  background-color: green;
}
#div4 {
  width: 130px;
  height: 130px;
  background-color: blue;
  border-radius: 50%;
  margin: -2%;
}