* {
  box-sizing: border-box;
}

.mainblock {
  overflow: scroll;
  border: 2px solid #000000;
  border-radius: 10px 0 0 10px;
  height: 500px;
  
}

.block {
  width: 200px;
  height: 200px;
  background: rgb(148, 136, 221);
  padding: 20px;
  margin: 10px;
  display: inline-block;
  border-radius: 20px;
  box-shadow: inset 0 0 10px;
}