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

body {
  font-family: 'Helvetica Neue', Helvetica, sans-serif;
  background: white;
  display: flex;
  justify-content: center;
  align-items: center;
  min-height: 100vh;
}

.calculator {
  background: rgb(60, 60, 60);
  border-radius: 30px;
  padding: 20px;
  width: 340px;
  box-shadow: 0 8px 8px black;
}

.display {
  background: rgb(40, 40, 40);
  color: white;
  font-size: 48px;
  text-align: right;
  padding: 30px 20px;
  margin-bottom: 20px;
  height: 100px;
  display: flex;
  align-items: center;
  justify-content: flex-end;
  border-radius: 12px;
  border: inset black;
}

.btn-container {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 12px;
}

.btn {
  border-radius: 50%;
  width: 64px;
  height: 64px;
  font-size: 32px;
  font-weight: 400;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: 0.3s;
}

.btn:active {
  scale: 0.95;
}

.btn.number {
  background: rgb(40, 40, 40);
  color: white;
}

.btn.number:hover {
  background: rgb(60, 60, 60);
}

.btn.operator,
.btn.equals {
  background: #ff9500;
  color: white;
}

.btn.operator.active,
.btn.equals.active {
  color: #ff9500;
  background: white;
}

.btn.operator:hover,
.btn.equals:hover {
  background: #ffbe64;
}

.btn.function {
  background: rgb(160, 160, 160);
  color: black;
}

.btn.function:hover {
  background: rgb(220, 220, 220);
}

.btn.zero {
  grid-column: span 2;
  border-radius: 32px;
  width: 100%;
  justify-content: flex-start;
  padding-left: 24px;
}

.controls {
  padding: 16px 8px;
  margin-bottom: 16px;
  background-color: wheat;
  color: rgb(40, 40, 40);
  border-radius: 12px;
  box-shadow: inset 0px 2px 4px;
}

.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  overflow: hidden;
}

@media (max-width: 375px) {
  .calculator {
    transform: scale(0.9);
  }
}