.box {
  position: relative;
  width: 400px;
  height: 400px;
  border: 3px solid black;
  margin: auto;
}

.bubble {
  position: absolute;
  width: 60px;
  height: 60px;
  border-radius: 50%;
  border: 2px solid black;
}

.arrow {
  position: absolute;
  width: 0;
  height: 0;
  border-style: solid;
  border-width: 15px 50px 15px 0;
  border-color: transparent black transparent transparent;
}

.btn {
  margin-top: 10px;
  background-color: green;
  color: white;
  width: 150px;
  height: 50px;
  margin-left: 45%;
  margin-bottom: 30px;
  border: none;
  border-radius: 5px;
  cursor: pointer;
}