*{
  padding: 0;
  margin: 0;
  box-sizing: border-box;
}

body{
  display: flex;
  justify-content: center;
  align-items: center;
  margin-top: 40px;
}

.calculator{
  border: 1px solid rgb(161, 154, 154);
  width: 400px;
  height: 600px;
}

.calculator h1 {
  text-align: center;
  font-size: 50px;
}

#display-area{
  height: 50px;
  width: 350px;
  margin-top: 10px;
  margin-left: 24px;
  font-size: 30px;
}

.cal-buttons{
  display: flex;
  justify-content: center;
  flex-wrap: wrap;
}

.btn{
  width: 80px;
  height: 60px;
  margin: 10px;
}