* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}
body {
  background: rgb(201, 218, 234, 0.5);
}
.calculator {
  margin: 4rem auto;
  padding: 2rem 1rem;
  height: 500px;
  width: 350px;
  display: grid;
  grid: repeat(6, 1fr) / repeat(4, 1fr);
  grid-gap: 10px;
  text-align: center;
  background: #03254e;
  border-radius: 15px;
  box-shadow: 10px 13px 10px #fcfff7;
}
.display,
.btn {
  border: none;
  outline: none;
  border-radius: 7px;
  font-size: 2rem;
  color: #011c27;
  display: flex;
  align-items: center;
}
.display {
  padding: 0 10px;
  grid-area: 1/1/2/5;
  width: 100%;
  justify-content: left;
  background: #f8f8f8;
}
.btn {
  background: #d3d5d7;
  justify-content: center;
  box-shadow: 0 4px #666;
}
.btn:active {
  box-shadow: 0 2px #666;
  transform: translateY(2px);
}
.number:hover {
  background: #e5fcff;
}
.changeNumBackground {
  background: #e5fcff;
}
.clear:hover,
.backspace:hover,
.operator:hover,
.equal:hover {
  background: #7ea8be;
}
.changeBtnBackground {
  background: #7ea8be;
}
.clear {
  grid-area: 2/1/3/3;
}
.zero {
  grid-area: 6/1/7/3;
}
.selected {
  background: #7ea8be;
}