*, *::before, *::after {
  box-sizing: border-box;
  font-family: "Georgia", serif;
  font-weight: 400;
  font-size: 14px;
}

body {
  padding: 0;
  margin: 0;
  background: linear-gradient(to top, #000080, #81D8D0);
}

.calculator-grid {
  margin: 0 auto;
  display: grid;
  width: 350px;
  min-height: 100vh;
  grid-template-columns: repeat(4, 80px);
  grid-template-rows: minmax(100px, auto) repeat(6, 70px);
  grid-gap: 10px;
  background-color: white;
}

.prompt-label {
  display: block;
  position: absolute;
  top: 20%;
  right: calc((100% - 430px) / 2);
  transform: translate(-30%, -20%);
  width: 20px;
  height: 20px;
  border-radius: 50%;
  border: 2px solid #2F2F2F;
  padding-top: 1px;
  padding-left: 4px;
  color: white;
  background-color: #191919;
}

.prompt-label:hover {
  cursor: pointer;
  background-color: #2F2F2F;
}

.prompt-label:hover + .prompt {
  opacity: 1;
  transition: 2s;
}

.prompt {
  display: block;
  opacity: 0;
  position: absolute;
  top: 15%;
  right: calc((100% - 1050px) / 2);
  padding: 10px;
  border-radius: 20px;
  font-size: 1.2em;
  width: 250px;
  color: white;
  background-color: #2F2F2F;
}

.prompt:hover {
  cursor: default;
}

.calculator-grid > button {
  cursor: pointer;
  font-size: 2rem;
  border: none;
  border-radius: 5px;
  outline: none;
  background-color: #B8D6FD;
}

.calculator-grid > button:hover {
  background-color: #8095B1;
}

button.operator {
  background-color: #D1FF19;
}

button.operator:hover {
  background-color: #A7CC14;
}

button.del {
  background-color: #FF3232;
}

button.del:hover {
  background-color: #B22323;
}

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

.span-four {
  grid-column: span 4;
}

.output {
  grid-column: 1 / -1;
  background-color: rgba(0, 0, 0, .75);
  display: flex;
  align-items: flex-end;
  justify-content: space-around;
  flex-direction: column;
  padding: 10px;
  word-wrap: break-word;
  word-break: break-all;
}

.output .previous-operand {
  color: rgba(255, 255, 255, .75);
  font-size: 1.5rem;
}

.output .current-operand {
  color: white;
  font-size: 2.1rem;
}