.calculator {
  width: 300px;
  margin: 50px auto;
  background: #000;
  border-radius: 20px;
  padding: 20px;
  box-shadow: 0 10px 30px rgba(0,0,0,0.3);
}

.calculator__display {
  background: #000;
  color: white;
  font-size: 70px;
  text-align: right;
  padding: 20px 10px;
  font-family: 'Helvetica Neue', sans-serif;
  font-weight: 300;
  overflow-x: auto;
  white-space: nowrap;
}

.calculator__keys {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 10px;
  padding: 10px;
}

button {
  background: #333;
  color: white;
  border: none;
  font-size: 30px;
  padding: 20px;
  border-radius: 50px;
  cursor: pointer;
  transition: all 0.2s;
  font-family: 'Helvetica Neue', sans-serif;
}

button:active {
  transform: scale(0.95);
}

.key--operator {
  background: #f0a33b;
}

.key--operator.is-depressed {
  background: #fff;
  color: #f0a33b;
}

.key--equal {
  background: #f0a33b;
}

button[data-action="clear"] {
  background: #9e9e9e;
  color: #000;
}

button[data-action="decimal"] {
  background: #333;
}

button:not(.key--operator):not(.key--equal):not([data-action="clear"]):not([data-action="decimal"]) {
  background: #505050;
}

button:hover {
  opacity: 0.8;
}