*,
*::before,
*::after {
  box-sizing: border-box;
  font-family: "Poppins", sans-serif;
  font-weight: normal;
}
body {
  padding: 0;
  margin: 0;
  background: linear-gradient(to right, #31427c, #851b1b);
}

.calculator-grid {
  display: grid;
  justify-content: center;
  align-content: center;
  min-height: 100vh;
  grid-template-columns: repeat(4, 100px);
  grid-template-rows: minmax(120px, auto) repeat(6, 100px);
}

@media (max-width: 767px) {
  .calculator-grid {
    grid-template-columns: repeat(4, 23%);
    grid-template-rows: minmax(100px, auto) repeat(6, 90px);
  }
}

.calculator-grid > button {
  cursor: pointer;
  font-size: 2rem;
  border: 2px solid rgba(0, 0, 0, 0.85);
  outline: none;
  background-color: rgb(132, 136, 145);
}
.calculator-grid > button:hover {
  background-color: rgba(255, 255, 255, 1);
}

.span-two {
  grid-column: span 2;
}

.output {
  grid-column: 1 / -1;
  grid-row: 1 / 3;
  background-color: rgba(3, 4, 15, 0.85);
  display: flex;
  align-items: flex-end;
  flex-direction: column;
  padding: 20px;
  word-wrap: break-word;
  word-break: break-all;
  justify-content: center;
}

.output .previous-operand {
  color: rgba(255, 235, 255, 0.75);
  font-size: 1.7rem;
}

.output .current-operand {
  color: white;
  font-size: 2.5rem;
}