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

body {
  font-family: "Helvetica Neue", sans-serif;
  width: 100vw;
  height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
}

.calculator {
  background: black;
  border-radius: 50px;
  color: white;
  height: 800px;
  width: 80%;
  max-width: 500px;
  padding: 1rem;
  display: flex;
  flex-direction: column;
  align-items: center;
}

.display {
  height: 15rem;
  width: 100%;
  text-align: right;
  padding: 1rem;
  font-size: 4rem;
  display: flex;
  flex-direction: column;
  justify-content: space-evenly;
}
.previous-display {
  opacity: 0.5;
  font-size: 1.5rem;
  overflow: hidden;
}

.buttons-container {
  width: 100%;
  display: grid;
  grid-gap: 0.5rem;
  grid-template-columns: repeat(4, 1fr);
  grid-template-rows: repeat(5, 1fr);
}

.button {
  display: flex;
  align-items: center;
  justify-content: center;
  background: #333;
  border-radius: 50%;
  cursor: pointer;
  font-size: 3rem;
  height: 6rem;
  width: 6rem;
  transition: filter 0.3s;
}

.button.function {
  color: black;
  background: #a5a5a5;
}

.button.operator {
  background: #f1a33c;
}

.button.number-0 {
  border-radius: 3rem;
  grid-column: 1 / span 2;
  justify-content: flex-start;
  padding-left: 2rem;
  width: 12rem;
}

.button:hover {
  opacity: 0.5;
}

@media screen and (max-width: 576px) {
  .calculator {
    width: 350px;
    height: 600px;
  }
  .display {
    height: 10rem;
    font-size: 3rem;
  }

  .button {
    font-size: 1.7rem;
    height: 4rem;
    width: 4rem;
  }
  .button.number-0 {
    border-radius: 2rem;
    padding-left: 1.3rem;
    width: 8rem;
  }
}