:root {
  --primary-color: #ed7014;
  --light-grey: #ddd;
}
*,
*::after,
*::before {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

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

.calculator {
  background: #999;
  width: 300px;
  height: 500px;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: space-evenly;
  box-shadow: 2px 2px 10px 3px rgba(0, 0, 0, 0.3);
  border-radius: 10px;
}

.calculator__display {
  width: 90%;
  height: 20%;
  background: #333;
  color: #ddd;
  box-shadow: 2px 2px 3px 1px rgba(0, 0, 0, 0.3);
  display: flex;
  font-size: 2rem;
  padding: 1rem 0.5rem;
  text-align: right;
  justify-content: flex-end;
  align-items: center;
  border-radius: 15px;
  overflow: auto;
}

.calculator__keys {
  width: 90%;
  height: 70%;
  display: grid;
  grid-template-columns: repeat(4, 1fr);
}

.key {
  border-radius: 15px;
  margin: 0.2rem;
  border: none;
  font-size: 1.2rem;
  box-shadow: 2px 2px 3px 1px rgba(0, 0, 0, 0.3);
  background: #ddd;
}

.key:active {
  box-shadow: none;
  background: #ccc;
  transform: scale(0.9);
}

.key:nth-child(6) {
  grid-column: 4;
}

.key:nth-child(5) {
  grid-column: 4;
}

.key:nth-child(9),
.key:nth-child(8),
.key:nth-child(7) {
  grid-row: 2;
}

.key:nth-child(12),
.key:nth-child(11),
.key:nth-child(10) {
  grid-row: 3;
}

.key:nth-child(16) {
  grid-row: 5;
  grid-column: span 2;
}

.key:nth-child(17) {
  grid-row: 5;
}

.key:last-child {
  grid-row: 4 / span 2;
}

.key--result {
  background-color: var(--primary-color);
  color: #ddd;
}

.key--operator {
  color: var(--primary-color);
}

.key--result:active {
  background: rgb(223, 97, 8);
}