html {
  font-size: 62.5%;
  box-sizing: border-box;
}

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

body {
  background-color: #1e1e1e;
}

.calculator {
  background-color: #444444;

  border: 3px solid #030303;
  border-radius: 5px;
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  width: 400px;
  padding: 2rem;
}

.display {
  font-family: "Press Start 2P", cursive;

  display: flex;
  background-color: darkolivegreen;
  border: 2px solid black;
  color: #1b1b1b;
  border-radius: 5px;

  font-size: 5rem;
  height: 80px;
  padding: 0 10px;
  margin-bottom: 1rem;
}
.display * {
  font-size: 3rem;
  display: flex;
  justify-content: center;
  align-items: center;
}
.display :nth-child(1) {
  margin-right: auto;
}
.result {
  display: block;
  margin-top: 1rem;
  font-size: 1.5rem;
}

.buttons {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  grid-gap: 0.5rem;
}

.buttons button {
  font-weight: 600;

  height: 60px;
  background-color: #282828;
  border-radius: 3px;
  border: 2px solid #030303;
  font-size: 3rem;
  color: #b3b3b3;
}

.buttons button:hover {
  background-color: #444444;
}

.buttons .all-clear {
  background-color: #f0595f;
  color: #fff;
}

.buttons .all-clear:hover {
  background-color: #f17377;
}

.buttons .equal {
  background-color: #c06d2e;
  color: #fff;
  height: 100%;
  grid-row-start: 4;
  grid-row-end: 6;
  grid-column-start: 4;
}

.buttons .equal:hover {
  background-color: #d28245;
}