html {
  font-size: 62.5%;
  box-sizing: border-box;
  background: #1C1C1C;
}

*, *::before, *::after {
  margin: 0;
  padding: 0;
  box-sizing: inherit;
}

button:focus, button.form-control:focus {
  outline: none !important;
  outline-width: 0 !important;
  box-shadow: none;
  -moz-box-shadow: none;
  -webkit-box-shadow: none;
}

.calculator {
  border-radius: 5px;
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  width: 400px;
}

.calculator-keys {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  grid-gap: 20px;
  padding: 20px;
}

#display {
  width: 100%;
  font-size: 7rem;
  height: 80px;
  border: none;
  background: #1C1C1C;
  color: #fff;
  text-align: right;
  padding-right: 20px;
  padding-left: 10px;
}

button {
  height: 75px;
  border-radius: 50%;
  font-size: 2.5rem;
  border: none;
}

.operators {
  color: white;
  background-color: #FF9500;
}

#divide:hover, #multiply:hover, #equals:hover, #plus:hover, #minus:hover {
  color: #FF9500;
  background-color: white;
}

.numbers, .decimal {
  background-color: #505050;
  color: white;
}

.lightGrey {
  background-color: #D4D4D2;
  color: #1C1C1C;
}

.zero {
  background-color: #505050;
  color: white;
  grid-row-start: 5;
  grid-row-end: 5;
  grid-column-start: 1;
  grid-column-end: 3;
  border-radius: 40px;
  text-align: left;
  padding-left: 15%;
}